Victoria River Research Station
Kidman Springs Field Day 2012
Hand Book
Victoria River Research Station, Kidman Springs Field Day
Wednesday 1st August 2012
Local Research, Local Knowledge…
Wednesday 1st August 2012
Time
9.30-10.00
10.00-10.15
Activity
Smoko and Registration
Welcome and Opening address
10.15-11.00
Northern Grazing Systems – Synopsis of rangelands research
that has been completed including a producer presentation on
the benefits of working in collaboration with researchers
Crossbreeding – the use of different breeds to meet our desired
outcomes e.g. fertility, polledness, weight gain
Breeding the horns out of your herd – Polledness 101 and
practical considerations
11.00-11.30
11.35-12.05
12.05-13.00
13.00-13.15
13.15-13.40
13.45-14.45
Lunch
Q and A session on heifers, the launch of the Heifer
Management in northern beef herds manual
Breeder Mortality – outcomes from the Breeder Mortality Study
Short Talks:



Cost effective HGP strategies – Producer Demonstration Site
Weaner management and the launch of the weaner book
Brunchilly Phosphorus trial – Interim results
14.45-15.15
Factors affecting the live weight gain of steers in northern
Australia – results from NT Live Weight Gain project
15.15-15.45
15.45-16.45
Afternoon Smoko
Profitable supplementation – realistic supplementation
strategies for the NT
16.45-18.15
Station Tour – talks on Selected Brahmans and Shruburn
– the results from 20 years of burning
Speakers
Richard Galton,
Keith Holzwart –
Avago
Dionne Walsh, Dan
Sedon –Limbunya
Tim Schatz
Trisha Cowley,
Roxie Holzwart –
Avago
Tim Schatz
Nigel Perkins
Trisha Cowley
Kieren McCosker
Casey Collier
Nigel Perkins
Garry Riggs –
Lakefield
Matt Callaghan
Rohan Sullivan –
Cave Creek
Tim Schatz
Dionne Walsh
Thursday 2nd August 2012
Time
8.00-10.00
Activity
Break out session – Supplementation
Bring along your figures to discuss options for your business with DoR staff
Enquiries please contact:
Whitney Dollemore
Phone 08 8973 9749
Email whitney.dollemore@nt.gov.au
Alison Haines
Phone 08 8975 0762
Email: alison.haines@nt.gov.au
Table of Contents
Resilient Businesses – from the ground up …………………………………………………………2
Northern grazing systems and Climate Clever Beef projects – giving pastoralists the
ability to improve or maintain land condition without compromising on profitability
Crossbreeding to improve production in the NT…………………………………………………5
The purposes of crossbreeding to overcome environmental or genetic constraints to
production, Case study: Senepol Brahman cross
Breeding the horns out of your herd…………….…………………………………………………12
Understanding Polled genetics, testing and application in a breeding situation
NT Heifer Research……………………………………………………………………………………………18
Introducing “Heifer management in northern beef herds” – available from MLA
Outcomes from the Breeder Mortality Study……………………………………………………20
What is the true extent of breeder mortality in northern Australia and effectiveness of
strategies to reduce breeder mortality?
Expected growth results from HGPs at the Hayfield PDS…………………………………28
HGP results and strategies based on the Producer Demonstration Site at Hayfield Station
Weaner Management in northern beef herds…………………………………………………34
Introducing “Weaner management in northern beef herds” – available from MLA
Validation and demonstration of a diagnostic tool for phosphorus status of beef
cattle in northern Australia……………………………………………………………....................36
Brunchilly Phosphorus trial design and results to date
Factors affecting liveweight gain in north Australian beef herds………………………39
Main findings from the Liveweight Gain Project investigating factors that affect the
performance of growing steers from weaning to turnoff
The Selected Brahmans…………..…………………………………………………………………………43
Comparison between selected brahmans and breed average
Managing Woody Vegetation Using Fire in the Victoria River District………………46
Frequency of burning effects on woody thickening and pasture composition
VRRS (Kidman Springs) Field Day Handbook 2012
Page 1
Resilient businesses – from the ground up
Dionne Walsh – Rangeland Program Coordinator – Darwin – dionne.walsh@nt.gov.au
Introduction
Unfortunately, today we see many businesses in the northern beef industry under great
pressure. Property values have fallen since the global financial crisis which has eroded business
equity for many. The enforcement of the 350kg weight limit to Indonesia has also impacted
heavily on the cash flows of beef businesses that are remote from domestic markets. The VRD is
no exception and about 25% of the properties in the district are currently for sale in what has
traditionally been a tightly-held area.
So it comes as no surprise to hear northern beef producers telling us they need to run high cattle
numbers and have every bit of their country in production to service debt and/or remain viable
(Walsh 2009). But what they are also telling us is that they are worried that they might be
putting undue pressure on their pastures as a result. This is a sombre backdrop to the message
that maintaining good land condition will be essential for running a profitable and productive
enterprise in the VRD in the long term (Whish et al. 2012).
Local Research, Local Knowledge
Over the past three years, the Northern Grazing Systems and Climate Clever Beef projects have
been investigating local solutions to four common issues impacting on the productivity,
profitability and sustainability of the industry. The project identified several “best bet”
recommendations for the VRD based on their economic performance and their ability to
improve and maintain land condition for the long term:
ISSUES
The constant challenge of matching animal
demand to pasture supply
Significant areas of “C” (poor) land condition
Under-utilised pastures too far from water
Woody vegetation thickening
BEST BET RECOMMENDATIONS
Stock close to the long term carrying capacity of
paddocks and make only moderate adjustments
to stock numbers seasonally in response to feed
conditions
Wet season spell one year in four, and use
stocking rates consistent with long term
carrying capacity
Develop new water and paddock infrastructure
- in the most productive country first
Use fire to manage woody vegetation and keep
pastures in good condition on affected land
types
Although these recommendations are based on very solid research and are used by many
successful producers, others have told us that adoption rates are low because they can’t afford
to reduce stocking rates, burn cattle feed or lock up country. Thus, strategies that will allow
producers to run safe stocking rates whilst maintaining or improving turn-off will be a
prerequisite to adoption of practices that will improve and maintain the pasture asset.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 2
So where will the productivity gains come from?
The main opportunities available to VRD producers include much of which is being covered at
this field day:




Improving breeder herd performance by reducing mortality rates and increasing
branding rates - strategies include selecting breeders for fertility, bull selection, early
weaning, increasing heifer fertility rates, using improved pastures, strategic
supplementation, optimising pasture quality and bulk.
Improving live weight gain and reducing turnoff time – strategies include genetic
selection, establishing improved pastures, strategic supplementation, HGPs, optimising
pasture quality and bulk, finishing cattle elsewhere.
Increasing sale returns and/or reducing operating costs.
Increasing carrying capacity on properties that aren’t currently fully developed by
reducing paddock size and/or increasing the watered area of paddocks.
But which of these are most relevant to my business?
Every business is different and there’s an enormous number of things to spend money on. How
can producers identify the options that will deliver the biggest bang for their investment buck?
The Department of Resources recently used funding from the Climate Clever Beef project to test
a process for identifying options with a business in the VRD. We worked with an agribusiness
consultant and the manager and owner to benchmark the current economic and herd situation
and identify areas for potential improvement. A range of practical options was identified and the
likely performance of each of these was tested via herd and economic modelling. This process
helped to clarify which options would provide the best return on investment and some of these
options are now being implemented on the property. Producers wishing to learn more about
business planning and benchmarking are encouraged to attend a Business EDGE workshop (for
more details contact DoR Katherine or check the MLA website).
A look to the future
As part of the Climate Clever Beef funding from the Australian Government, we are required to
assess the greenhouse gas emissions performance of the productivity options identified above.
Early modelling indicates that improving breeder herd performance and increasing cattle growth
rates both reduce emissions intensity. This may be relevant to the future participation of
northern beef producers in the Australian Government’s “Clean Energy Legislative Package”. As
part of this package, primary producers will be encouraged to generate income through reducing
greenhouse gas emissions or increasing carbon storage. The DoR has recently received funding
from the Carbon Farming Initiative Program to determine (1) what opportunities are realistically
available for northern beef producers to participate in the carbon economy and (2) whether
there is a business case for them to do so. The three-year project is expected to provide
independent, evidence-based advice for northern beef producers in these uncertain times.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 3
Acknowledgements
The Northern Grazing Systems and Climate Clever Beef projects have been funded by the NT
Department of Resources, the Australian Government and Meat & Livestock Australia. The
collaboration of producers in the VRD is gratefully acknowledged.
References
Walsh, D. (2009). ‘Northern Grazing Systems project. Victoria River District & East Kimberley
region. Report of Workshop 1, Katherine Research Station, 20th April 2009’. Department of
Regional Development, Primary Industry, Fisheries & Resources, Katherine.
.
Whish, G., Pahl, L., Cowley, R., Scanlan, J. & MacLeod, N. (2012)
Bio-economic modelling of
climate change impacts and identification of promising adaptive management strategies. Final
Report for “Developing improved on-ground practices and industry strategies for adapting to
climate change within beef production enterprises across northern Australia”. Project B.NBP.
0616. Meat & Livestock Australia, Brisbane.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 4
Crossbreeding to improve production in the NT
Tim Schatz – Principal Pastoral Production Officer – Darwin – tim.schatz@nt.gov.au
Crossbreeding can be used to increase cattle production through combining the desirable
attributes of different breeds (eg. heat tolerance, tick resistance, fertility, growth rate) and to
produce hybrid vigour (also known as heterosis). Hybrid vigour is the improvement in
performance of crossbred offspring over the average performance of the parental breeds. It is
greatest in the first (F1) generation and declines in subsequent generations if the offspring are
back crossed to either of the parental breeds or are interbred to form a stabilised breed. The
loss of hybrid vigour is less if more breeds are involved in the cross and this reason for
multibreed composites.
Different breeds and combinations of breeds have different traits and attributes that make them
better suited to different environments. Generally Brahman and other Bos indicus breeds have
superior resistance to heat, ticks, intestinal parasites and buffalo fly, can walk longer distances
and are more efficient at digesting low-quality pastures. However, they have lower potential for
fertility and growth under more favourable conditions than Bos taurus breeds. In northern
Australia the most productive genotype often has a combination of the adaptive attributes of
the Bos indicus and the productive attributes of the Bos taurus. The most productive genotype
varies with the environment but in general, the harsher the conditions the higher the Bos indicus
content that is required.
In the past attempts have been made to crossbreed with pure British breed Bos taurus bulls (eg.
Angus, Hereford) with Brahman cows in the tropical north but the bulls have often not been able
to survive and produce calves. Now days there are a number of tropically adapted Bos taurus
breeds or Sangas (eg. Tuli, Belmont Red, Senepol, Boran), that are better suited to harsher
environments can be used as bulls in crossbreeding programs in northern Australia.
The DoR has done crossbreeding research with a number of different breeds over the years (eg.
Charolais, Tuli, Belmont Red, and Composites) however currently it has a major crossbreeding
project underway with Senepols. The aim of this project is to investigate whether crossbreeding
Senepol bulls and Brahman cows (current NT commercial genotypes) will produce offspring that
perform well under NT conditions and have better meat quality than pure Brahmans. If this is
the case then this strategy would increase the marketing options for NT cattle stations as they
could produce cattle that would be in demand in both the live export and Australian domestic
markets.
The Senepol breed was formed around 100 years ago on the island of St Croix in the Caribbean
when the N’dama (a native Bos taurus from Senegal, North West Africa) was crossed with the
British breed, Red Poll. The environment on St Croix has both wet tropics with high humidity and
rainfall and hot, dry savanna country. Tropical parasites and cattle tick are abundant and the
native feed low in quality. Natural selection under these conditions produced a tropically
adapted Bos taurus breed. Senepols are also naturally polled.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 5
The NT Senepol crossbreeding project has been underway since late 2008 when Senepol Bulls
were mated to Brahman cows for the first time in the NT Department of Resources herds at
Victoria River Research Station and Manbulloo (NT DoR leases a paddock at Manbulloo). The first
year group of calves was weaned in 2010 and the last year group will be weaned in 2013 (ie. the
past 2011/12 wet season is the last time the Senepol bulls will be used).
The project is still quite a way from completion but results so far are:
Weaning weight
In each year the average weight of the F1 Senepol cross first round weaners was heavier than
the Brahman weaners. At VRRS the F1 Senepol cross calves were an average of 23 kg heavier
than Brahman calves over 3 years (Table 1). At Manbulloo the F1 Senepol cross calves were an
average of 19 kg heavier than Brahman calves over 2 years (Table 2).
Table 1. Average weaning weights of calves weaned at VRRS at the first weaning round
(number in brackets).
2010
2011
2012
Brahman
178 (137)
184 (123)
200 (176)
F1 Senepol
196 (38)
204 (143)
230 (193)
+18 kg
+ 20 kg
+ 30 kg
Difference (F1 Sen)
Table 2. Average weaning weights of calves weaned at Manbulloo at the first weaning round
(n in brackets).
2010
2012
Brahman
153 (114)
181 (82)
F1 Senepol
173 (39)
200 (35)
+19 kg
Difference (F1 Sen)
+ 20 kg
*There was an insufficient number of animals with data available weaned at Manbulloo in 2011 to
present.
Post weaning performance of heifers
Each year shortly after weaning the heifers that had been born at Manbulloo were transported
to VRRS and added to the heifers that were born at VRRS. From that point onwards each year
group of heifers were managed together in one group.
Performance of 2010 weaned (#10) heifers at VRRS (native pasture)
The raw data shows that on average the #10 F1 Senepol x Brahman heifers were heavier at
weaning (184 kg vs 166 kg), grew more over the post weaning dry season (14 kg vs 6 kg), and
grew slightly more over the following wet season (104 kg vs 100 kg). By the time that the pre
joining weight was recorded on 6/9/11 the F1 Senepol heifers were on average 31 kg heavier
than the Brahmans and their resultant pregnancy rates were 10% higher (94% vs 84%) (Table 3).
VRRS (Kidman Springs) Field Day Handbook 2012
Page 6
Table 3. Performance of #10 Brahman and F1 Senepol cross heifers at VRRS.
N
Avg
Wean Wt
(kg)
165.8
184.0
Avg DS
Growth
2010 (kg)
5.7
14.3
Avg WS Growth
2010/11
(kg)
100.0
104.4
Avg Pre Join
Wt 6/9/11
(kg)
299.7
331.2
Avg Post Jn
Wt* 18/5/12
(kg)
404.8
441.9
Pregnancy
rate
(%)
84
94
Brahman 122
F1
33
Senepol
DS (Dry season) Growth = from 25/5/10 – 14/9/10, WS (wet season) Growth= from 14/9/10 – 27/4/11,
Post Jn = post joining. There were some animals that could not be included in the above data as they got
pregnant at the wrong time ie. a year earlier than intended.
Performance of 2011 weaned (#11) heifers at VRRS (native pasture)
The F1 Senepol cross heifers that were bred on VRRS were on average 22.1 kg heavier at
weaning, and on average grew 5.1 kg more than their Brahman counterparts over the following
(2011) dry season (DS). More heifers were added later on (some of which were from Manbulloo
and some were weaned at the 2nd round muster in September) and so it was possible to
calculate growth rates over the 2011/12 wet season for a greater number of animals (Table 4).
During this period (ie 11/9/11 to mid May 2012) on average the F1 Senepol cross heifers grew 15
kg more than the Brahman heifers (117.3 kg vs 102.3 kg). As a result on average the F1 Senepol
cross heifers are about 45 kg heavier a year after weaning than the Brahman heifers.
Table 4. Performance of #11 Brahman and F1 Senepol cross heifers at VRRS.
Brahman
F1 Senepol
difference
n VRRS
weaned
heifers
n All heifers
at WR1
2012
Avg Wt on
31/5/12
(kg)
Avg DS
growth
(kg)
86
41
133
68
175.9
198
+22.1 kg
0.9
6
+5.1 kg
Avg WS
growth (post
wean)
(kg)
102.3
117.3
+15.0 kg
Avg Wt
May 2012
(kg)
281
326
+ 45 kg
Post weaning performance of males.
Each year the 1st round male weaners from VRRS and Manbulloo were transported to the
Douglas Daly Research Farm (DDRF) shortly after weaning where they grazed improved Buffel
pasture for a year. They run together in the same paddocks (they were all a part of a cell grazing
mob that was rotated around paddocks) and were weighed periodically. Their post weaning
performance was recorded and is presented below.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 7
Growth of 2010 weaned steers at DDRF (improved pasture).
The average liveweight gain of steers weaned in 2010 is shown in Figure 1 and summarised in
Tables 5 and 6.
Figure 1. The growth of #10 F1 Seneopl cross and Brahman steers in the year after weaning at
DDRF.
Table 5. Full* growth of males at DDRF. (*Un-fasted weights were used to calculate growth).
Avg Wt
Avg DS
Avg Total growthF
F
F
Avg Wt
26/5/11
growth
Avg WS
(8/6/10 - 26/5/11)
n
8/6/10F (kg)
(kg)
(kg)
growthF (kg)
(kg)
Cell Bra
74
160.2
321.0
15.9
144.4
160.3
F1 Senepol
31
185.7
353.2
14.3
152.6
167.5
difference
25.5
32.2
-1.6
8.2
7.3
DS (Dry season) Growth = from 8/6/10 to 26/10/10, WS (wet season) Growth = from 26/10/10 to 26/5/11.
Table 6. “Empty”* growth of males at DDRF. (*Fasted weights are used to calculate growth –
ie. animals were curfewed over night before weighing the next day).
Cell Bra
F1 Senepol
Difference
n
74
31
Avg WtE
9/6/10
(kg)
154.5
177.5
23.0
Avg WtE
21/6/11
(kg)
315.6
343.3
27.7
Avg DS
growthE
(kg)
10.1
9.9
-0.2
VRRS (Kidman Springs) Field Day Handbook 2012
Avg WS
growthE
(kg)
151.1
155.8
4.7
Avg Total growthE
(9/6/10 - 27/5/11)
(kg)
161.2
165.7
4.5
Page 8
As can be seen from Figure 1 and Tables 5 and 6 the F1 Senepol cross steers were heavier at the
start (+25 kg) and grew slightly more over the post weaning year (+7 kg) on improved pasture at
DDRF. As a result at the end of the post weaning year they were on average 32 kg heavier (using
un-fasted weights) than the Brahman steers that they grazed with. Fat depth at the P8 site was
measured ultrasonically at the end of the trial period and the average fat depths were very
similar (3.3 mm for the F1 Senepol cross steers and 3.7 mm for the Brahman steers).
Growth of 2011 weaned steers at DDRF (improved pasture).
The steers which were weaned in 2011 were managed in the same way as those weaned in 2011
(ie. the 2 genotypes grazed together on improved pasture at DDRF as part of a mob being
rotated around paddocks in a cell grazing operation. The main difference was that the cattle
were kept longer than usual due to the live export situation.
As can be seen from Figure 2 and Tables 7 and 8 the F1 Senepol cross steers were heavier at the
start (+17 kg) and grew slightly more over the post weaning year (+15 kg) on improved pasture
at DDRF. As a result at the end of the post weaning year they were on average 31 kg heavier
(using un-fasted weights recorded on 1/5/12) than the Brahman steers that they grazed with.
Fat depth at the P8 site was measured ultrasonically at the end of the trial period and the
average P8 fat depths were lower for the F1 Senepol cross steers (2.9 mm) than the Brahman
steers (4.3 mm).
Figure 2. The growth of #11 F1 Seneopl cross and Brahman steers in the year after weaning at
DDRF.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 9
Table 7. Full* growth of steers at DDRF. (*Un-fasted weights were used to calculate growth).
n
Avg Wt
18/7/11
Avg Wt
1/5/12
330.6
Avg
Wt
3/7/1
2
337.4
Avg DS
GrowthF
(19/10/11 18/7/11)
4.8
Avg WS
growthF
(1/5/12 19/10/11)
120.2
Avg Total
growthF
(1/5/12 –
18/7/11)
125.3
F1 Senepol
58
205.1
Brahman
46
188.1
299.4
313.5
-0.3
110.5
110.1
17.0
31.2
23.9
5.0
9.7
15.2
difference
Table 8. “Empty”* growth and P8 fat depth of steers at DDRF. (*Fasted weights are used to
calculate growth – ie. animals were curfewed over night before weighing the next day).
Avg Total growthE
(4/7/12 - 19/7/11) (kg)
P8 fat
4/7/12
(mm)
F1 Senepol
125.3
2.9
Brahman
119.9
4.3
5.5
-1.4
Difference
Incidence of polledness in progeny
At the start of the project the current thinking was that all the F1 progeny should be polled. This
work has found that this is not the case however; the majority of animals are polled. Only a very
small percentage (<5%) grow horns and the rest have scurrs that don’t seem to get longer than
about 5cm. The horn status of the progeny is summarised in the following tables.
Table 9. Incidence of polledness in F1 Senepol cross Brahman offspring.
Gender
Females
Males
Year weaned
2010
Polled
Scurred
Horned
N
79%
13%
8%
2011
66%
33%
1%
38
79
2012
69%
28%
2%
88
All years
2010
70%
81%
27%
13%
3%
6%
205
31
2011
62%
32%
6%
53
2012
39%
57%
3%
105
53%
43%
4%
188
All years
VRRS (Kidman Springs) Field Day Handbook 2012
Page 10
Coat colour
Most of the cross bred progeny ranged from dark red to yellow but a few were black or creamy
and some were brindle (about 11% of the 2012 weaned males were brindle).
Calf siring ability of bulls
The common experience of cattle producers in northern parts of the NT in the past is that pure
Bos taurus bulls have struggled with the conditions and not performed well in producing calves.
Our experience was that when the Senepol bulls were introduced to paddocks in which Brahman
bulls were already established that they appeared to be out-competed by the Brahman bulls,
and often about two thirds of the calves were sired by Brahman bulls. However when the
Senepol bulls were the only breed of bulls in the paddock they sired plenty of calves and
weaning rates were normal.
Preliminary observations/conclusions
-
-
-
The F1 Senepol cross calves were heavier at weaning than the Brahmans. This is a typical
result when crossbreds are compared to a pure breds due to hybrid vigour.
The F1 Senepol cross heifers appear to grow more than Brahman heifers following
weaning and so this combined with their heavier weaning weights means that they are
heavier at joining. Pregnancy rates were 10% higher in the F1 Senepol cross heifers in
the one year group that there is data for so far. However the number of heifers in that
1st year group is low (n=33), so while the data can give an indication of performance it
should not be relied on to draw solid conclusions (this can be done once data from
several year groups is available).
The performance of both year groups of steers (2010 and 2011 weaned) grazing
improved pasture at DDRF over the post weaning year showed that the F1 Senepol cross
steers grew slightly better than Brahmans (+7 kg and +15 kg in #10 and # 11 steers
respectively). This combined with their heavier weaning weights resulted in them being
considerably heavier (about 30 kg) at the end of the year after weaning.
These preliminary results indicate that the F1 Senepol cross progeny are performing
better than Brahmans in these conditions. The main reason for breeding these crossbred
animals was to produce animals that have better meat quality than pure Bos indicus
animals and hence increase the marketing options for producers. As they are 50% Bos
taurus they should grade better when assessed in Australian abattoirs and so be more
marketable in Australian domestic markets. The fact that F1 Senepol crossbred offspring
appear to perform at least as well as Brahmans in northern environments is important
for producers considering crossbreeding with Senepols.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 11
Breeding the horns out of your herd
Trisha Cowley – Pastoral Production Officer – Katherine – trisha.cowley@nt.gov.au
This article will first look at the inheritance of polledness and then will explore some of the
practical considerations of introducing polledness to your breeding program.
The Polled gene
In many Bos Taurus breeds (but not Bos indicus) a single gene determines whether animals are
polled or horned; the polled gene. The polled gene has 2 forms; polled (P) or horned (H). Every
animal has two copies of the polled gene, so potentially they could have PP, PH or HH. An
animal that has 2 of the same copies of the polled gene (e.g. PP or HH) is called homozygous,
while an animal that has one of each of form of the gene is heterozygous (e.g. PH). The polled
form is dominant over the horned form. This means that even if an animal has only one copy of
the polled form it is still visually polled (i.e. both PP and PH animals are visually polled). HH
animals are horned.
An animal gets one copy of the polled gene from its mother and one copy from its father, and
consequently randomly passes on one of its copies to its progeny. PP animals are considered
“true polled” as they pass on the polled copy to 100% of their progeny. However, PH animals
are carriers of horn, and will only pass on a polled copy to half of their progeny. Therefore, using
PP sires in preference to PH sires will speed up the time taken to reach a polled herd. Since PP
and PH animals look the same, it is desirable to be able to distinguish between them.
Several tests exist that can do just that, however they only work well in European breeds where
polledness is controlled by the polled gene only. Until recently there were no tests available that
worked in the Bos indicus breeds where the inheritance of polledness is more complex.
Inheritance of polledness in Bos indicus cattle
We still have more to learn about the inheritance of polledness in Bos indicus cattle. It was
thought that the inheritance of polledness was controlled by 3 unrelated genes: the “Polled”,
“African Horn” and “Scur” genes (scurs are loose horny growths that are not attached to the
skull). However, a study carried out by the Beef CRC, CSIRO and MLA found very little evidence
for the African horn gene in the animals studied. Further, it seems that the underlying genetics
of scurs acts in combination with the Polled gene in some breeds. We still don’t know too much
about the inheritance of scurs, but what we do know for certain is that Bos indicus animals (and
some Bos Taurus breeds such as Hereford) can be polled, scurred or horned due to the
interaction of the Polled gene with scurs. There is also some evidence that scurs are sex linked,
with scurs being more prevalent in males than females and that the prevalence of scurs differs in
different breeds and in different lines of cattle.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 12
Polled Gene Marker Test
Excitingly, a test has been released that works very well in Brahmans in determining whether
animals are true polled (PP) or carriers of horns (PH), regardless of the interaction of scurs. The
test uses gene markers (fragments of DNA that are not directly responsible for polled status, but
are closely associated with the polled gene) to determine whether an animal is PP, PH or HH.
The test also works well in Santa Gertrudis, Droughtmaster, Hereford and Simmental.
To assess the usefulness of the Polled Gene Marker Test, 402 animals from 38 Brahman studs
were tested and then their result was compared to their actual poll/horn status (i.e. what they
look like). The results are presented in Table 1 below.
Table 1: Percentage of Brahmans tested within the Polled Gene Marker validation studies that
were visually polled, scurred or horned
Genotype
PP
PH
HH
Visual Appearance
Polled Scurred Horned
(%)
(%)
(%)
98
1
1
40
50
10
2
6
92
Thus, in Brahmans scurred animals are highly likely be carriers of horns (PH) while polled animals
are likely to be homozygous polled (PP), but could also be heterozygous polled (PH).
It is important to note that the Polled Gene Marker Test does not provide a conclusive result
every time. In Brahmans, 11% of the test results were inconclusive (i.e. the test could not say
whether the animal was PP, PH or HH). Of all breeds tested, the Brahman had the least number
of ambiguous results. The test is currently being updated and researchers involved are confident
that the new test will have 99% accuracy in Brahmans and increased accuracy in other breeds.
How do I organise a Polled Gene Marker Test?
The Pfizer Animal Genetics arm and the University of Queensland Animal Genetics Laboratory
(through ABBA) both carry out Polled Gene Marker Testing. The cost per animal is
approximately $30 and involves collecting a tail hair sample that is sent to the lab. After which,
you should receive your results in about 2-3 weeks. The test is currently only suitable for use in
Brahman, Santa Gertrudis, Droughtmaster, Hereford and Simmental breeds (and any
combination of them).
What can you expect from using PP, PH or HH Brahman bulls?
Most Brahman herds will be largely HH, with very little polled influence. Obviously using a PP
bull will infuse the largest amount of polled genetics into a herd. For example, PP sires over HH
cows will give 100% PH progeny, whereas on average PH sires over HH cows will give you 50%
PH progeny and 50% HH progeny.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 13
Table 2: Expected percentage of Brahman progeny that will be PP, PH or HH for different
poll/horn crosses
Potential
polled/horned
crosses
PP x PP
PP x PH
PP x HH
PH x PH
PH x HH
HH x HH
Genotype of resulting Brahman progeny
% Progeny PP
% Progeny PH
% Progeny HH
100
50
0
25
0
0
0
50
100
50
50
0
0
0
0
25
50
100
While Table 2 displays the genetic make-up of the progeny, it doesn’t show what percentage of
animals that will be visually polled, scurred or horned. This is displayed in Table 3.
Table 3: Expected percentage of Brahman progeny that will be polled, scurred or horned for
different poll/horn crosses
Potential
polled/horned
crosses
PP x PP
PP x PH
PP x HH
PH x PH
PH x HH
HH x HH
Visual appearance of resulting Brahman progeny
% Progeny
Polled
% Progeny
Scurred
% Progeny
Horned
98
69
40
44.5
21
2
1
25.5
50
27
28
6
1
5.5
10
28.5
51
92
Hence, on average a PP bull over HH cows will give you 40% polled progeny, 50% scurred and
10% horned, as opposed to a PH bull over HH cows which will give you 21% polled, 28% scurred
and 51% horned. As the prevalence of the African horn gene and scurs are thought to differ in
different breeds and in different lines of cattle, it is likely that the real world percentages will
differ to those depicted in Table 3. However, this is the best estimate that we can give based on
current knowledge. Regardless of the current prevalence of these, the use of true polled bulls
will reduce scurs and horns in your herd. The key message is that about 90% of progeny from PP
bulls and HH cows will not need dehorning, while about 50% of progeny from PH bulls and HH
cows will need dehorning. Using PP bulls will almost immediately solve your dehorning issues,
though it will take a lot longer to reach a 100% polled herd.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 14
So is it that simple?
It’s never that simple! While the use of PP bulls over PH and HH bulls will certainly move you
more quickly towards a polled herd, there are some considerations that should be taken into
account when planning a polled breeding program.
Let’s put polledness into perspective
Polledness has obvious advantages such as better welfare outcomes and increased productivity
and safety. However, it is not likely to be a trait that is critical to your bottom line, and as such
your selection methods should reflect this. The major traits of importance are those that drive
your profitability (reproductive performance and growth), those that ensure bulls will get calves
on the ground (structural and reproductive soundness), those that ensure you are producing a
product the market wants (carcass traits etc) and last but not least, temperament. Don’t choose
a bull because he is polled, choose a bull because he meets your primary breeding objectives
AND is polled.
How long will it take to achieve a polled herd?
Unfortunately the best answer to this question probably is “How long is a piece of string”. It will
depend on factors such as:
 the current proportion of polledness in your herd
 the proportion of PP, PH and HH bulls that you use
 the prevalence of the scur and African Horn gene in your herd/breed
 the current herd structure – are you still building up herd numbers?
 number of replacements retained – less heifers retained will mean less genetic progress
 calving and weaning percentages as this influences the potential number of
replacements
Without using the Polled Gene Marker Test it has been estimated that it would take about 35
years to achieve a 100% polled herd. However, if the test is used to select all PP bulls it is
estimated that it would take 8 years (assuming that female selection is based only on polledness,
that bulls are only used for 2 years and that heifers are yearling mated and are kept in the herd
for 7 years). In reality it is going to take longer in NT herds due to differences in management
and due to the availability of Brahman polled genetics. What we can be sure of is that the
journey is going to be a long one.
Availability of polled genetics
Currently the low prevalence of polled animals in the national Brahman herd (more so among
the greys than reds) means that if tomorrow everyone decided to start breeding polled, there
simply wouldn’t be enough PP or PH bulls to go around. High prices are already being seen, with
two polled Red Brahman bulls selling for $50 000 and $55 000 in 2011 and Brahman PP semen
selling for between $80-$200 per straw. Until more studs start breeding polled animals, prices
will stay high, particularly for PP bulls.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 15
It is currently very difficult to find polled Brahmans with estimated breeding values (EBVs - which
offer the best indication of an animal’s genetic merit for specific traits). Most operations will
need to select HH and PH sires as well as PP sires to source enough Brahman bulls that meet all
selection criteria.
Other tropically adapted breeds with strong polled lines include
Droughtmaster, Belmont Red, Senepol and Bonsmara.
Buyer beware!
As with any trend, when a particular trait or breed is in favour many people get on the band
wagon. There is a danger that some studs will attempt to cash in on the current demand for
polled genetics by hasty breeding programs without proper attention to other important traits.
Currently there are only a handful of studs that have a long history of breeding polled Brahmans.
The same principles apply with any bull purchasing venture – do your research! Establish a good
relationship with the stud and make sure their breeding philosophies match yours. Ask for
information on the bulls that will provide more evidence of their breeding value, such as dam
calving history, EBVs, BBSE and so on. And if you want PP bulls rather than PH – make sure they
are poll gene marker tested because you won’t know the difference by looking at them!!
Potential breeding strategies
Depending on your breeding goals, there are a number of strategies that could be used to
introduce polled genetics. You could introduce Brahman PH or PP sires to your herd, but you
will have difficulty sourcing them, particularly if looking for large numbers. Another option
within Brahman is to start a small nucleus bull breeding herd and introducing PP sires into it,
either through AI or natural mating. This breeding strategy is currently being demonstrated at
both Avago Station and Lakefield Station as part of a Producer Demonstration Site (PDS) looking
at the use of the Polled Gene Marker test to breed home grown polled bulls. The next article in
this series will cover Avago and Lakefield’s polled breeding strategies and their involvement in
this PDS.
Cross-breeding with a tropically adapted polled breed is another option which has the additional
benefits of hybrid vigour and potentially increasing market options. It could simply be a short
term solution to the lack of Brahman sires available, with the option to return to Brahman sires
in the future when more polled Brahmans are available.
Links between polledness and other traits
The major criticisms that polled cattle often cop is that they don’t have good bone, are small,
have poor growth, poor fertility, breeding soundness abnormalities, etc. However a review of all
scientific literature comparing polled to horned cattle did not find any evidence to support these
views. Polled Bos indicus cattle were found to have a higher incidence of pizzle injuries but this
was a function of sheath structure rather than a trait of polledness. Fortunately sheath
structure is moderately heritable so appropriate selection for sound sheath structure will
overcome potential issues. Like any breed, there are lines of lower quality cattle regardless of
the presence or absence of horns as the number of polled Brahmans increase there will be
greater opportunity to select animals that meet your specific breeding objectives.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 16
In summary
Breeding for polledness has many benefits, but it should be secondary to breeding for calves on
the ground, weight on the boat, cattle you can handle and a quality product that the market
desires. Current availability of polled Brahmans may mean looking at cross-breeding options, or
moving more slowly towards a polled Brahman herd through the use of PP, PH and HH sires.
Whatever your strategy, it will take a long time to achieve a 100% polled herd. The good news is
that in Brahmans the first cross of PP bulls over HH cows will result in about 90% of progeny not
requiring dehorning (scurred or polled), while PH bulls over HH cows will result in about 49% –
so you will see positive outcomes very quickly.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 17
NT Heifer Research
Tim Schatz – Principal Pastoral Production Officer – Darwin – tim.schatz@nt.gov.au
The NT heifer research projects were reported on in depth at the previous VRRS field day. Since
then a best practice manual for heifer management in northern Australia has been produced
and published. It is a concise, readable guide to best practice management written for graziers,
station managers, head and other stockmen and for students of animal husbandry.
Copies are available at the field day or:
Digital copies can be downloaded at:
http://www.mla.com.au/Publications-tools-and-events/Publication-details?pubid=5823
Hard copies can be ordered by calling the MLA membership services hotline on 1800 675 717 or
email publications@mla.com.au - or from the Department of Resources - Email:
technical.publications@nt.gov.au
VRRS (Kidman Springs) Field Day Handbook 2012
Page 18
Key messages for heifer Management:
Improving reconception rates in first calf heifers can significantly improve herd profitability.
General principles that can be applied to the management of replacement heifers include:
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Body condition at mating has the greatest effect on heifer fertility
Conservative stocking and good pasture in heifer paddocks are the cheapest ways to
achieve good body condition. Supplements may be cost effective.
Heifers should be segregated from the breeder herd, gazed on the best paddocks and
may need supplements over the post-weaning dry season to reach critical mating
weight.
The majority of heifers should be at or above the critical mating weight (CMW) at the
start of joining. The CMW for Bos indicus heifers is 320-340kg.
Bos indicus heifers tend to reach puberty at heavier weights and at a later age than Bos
taurus heifers.
The heifer needs to have a body condition score (BCS) of 3.5 (on a BCS scale of 1-5) or
higher at calving to maximise the chance of getting pregnant again while rearing her calf.
If heifers are selected before joining, this should be based on growth over the postweaning year, and not on weight at weaning, which largely depends on age.
Mate more heifers than are needed for replacements using young bulls evaluated for
breeding soundness, ‘calving ease’ and ‘low birth weight’.
Select replacement heifers from those that get pregnant early in the joining period – and
on temperament.
Ideally, heifers should be mated for only 3 cycles (63 days). On extensive properties,
pregnancy diagnosis can be used to identify heifers that conceived early in the mating
period.
Yearling mating will give good results only if heifers are heavy enough (on good country)
and are of early maturing breed types.
The best type of heifer will be suited to the environment and target market.
Genetic improvement is faster through crossbreeding than through selection.
Bull selection will have a much greater impact on herd improvement than selecting
heifers or cows.
Calf losses in first-calf heifers are often high (>20%) and mostly occur around the time of
birth.
Muster and wean first-calf heifers before the main breeder herd.
Wean calves early, down to 100kg (3 months), or even earlier if heifer survival is at risk.
Vaccinate all heifers against botulism and against any other diseases that could have
significant economic impact.
Maiden heifers are a good group to use if an artificial insemination program is planned.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 19
Outcomes from the Breeder Mortality Study
Nigel Perkins - AusVet Animal Health Services – nigel@ausvet.com.au
Alastair Henderson – Mirroong Pty Ltd, Steve Banney – Steve Banney Agribusiness
Introduction
Breeder mortality and reproduction rates directly influence herd productivity and enterprise
profit. Past RD&E and producer experience has demonstrated that annual breeder mortality
rates in extensive pastoral regions may exceed 10%, and that reduction in breeder mortality may
be possible through strategies such as early weaning, botulism vaccination, wet season
phosphorus (P), dry season urea (NPN) and conservative stocking rates. The recent NT Pastoral
Survey (2006) suggests that beef producers estimate average breeder and heifer mortality rates
at 3%.
There have been concerns that breeder mortality rates in the Northern Territory, Kimberley and
Pilbara regions of WA and possibly the north-west and north Qld could be much higher than
expected and may be an important factor limiting profitability for many properties in the Alice
Springs, Katherine and Pilbara regions.
Property-level mortality rates are particularly difficult, if not impossible to measure directly,
which may partially explain the disparity between general industry estimates and emerging
regional evidence.
This project aimed to quantify property-level breeder cow mortality throughout the extensive
pastoral regions of northern Australia. It has developed a simple, but robust indirect method of
retrospectively estimating breeder mortality over a period of at least 3 years using propertylevel herd and turnoff data combined with simple inventory analysis. Data was collected from a
sample of at least five properties identified throughout the NT, Kimberley and Pilbara regions of
WA and north-west and northern regions of Qld.
Method development
Initial approaches involved using BCOWPLUS and working with producers to get the model to
the point where it was replicating actual property level performance. BCOWPLUS is a steady
state herd model that assumes that the herd composition and size remains the same at the end
of the year as it was at the beginning. It represents a stabilised herd in which the same number
of heifers comes into the breeding herd every year, and the same numbers and classes of cattle
are turned off every year. The data used for BCOWPLUS should be average for a run of years.
There were a number of problems associated with this approach (lack of steady state, relatively
complicated model set up and parameterisation, involvement of assumptions concerning key
parameters in the model set up that were directly related to the outcomes we were interested
in).
VRRS (Kidman Springs) Field Day Handbook 2012
Page 20
A decision was made to use available livestock scheduling data (opening and closing counts of
cattle by class) in a simpler process that made fewer assumptions. The scheduling approach
involves collecting annual counts of cattle in a small number of classes. These data were entered
into a spreadsheet and then summed to produce totals over the period they were collected (3 to
9 years).
There were then two main assumptions. The first was that the percentage of deaths in nonbreeding females (such as weaner heifers) was 3% per year (3 deaths per 100 non-breeding
females). The second was that the total count of animals branded in a given year was made up
of 50% females and 50% males.
Opening females (Starting total female count)
Opening breeders
Branded (ans branded that year)
Female sales
Female purchases
Closing females from BOOK
Opening steers
Sales of steers
Purchase of steers
Closing steers from BOOK
ASSUMPTIONS
proportion of branded animals that are female
mortality rate in non-breeding females
CALCULATED CELLS
Est'd branded heifers (0.5*Branded)
Est'd branded steers (Branded - Est'd branded heifers)
Closing females from data (op_fem - fem_sales + fem_purch + brnd_heif)
Estimated deaths in all females (clos_fem_bk - clos_fem_data)
DENOMINATORS - females at risk of dying
Adj'd females at risk (op_fem+0.5*brd_heif+0.5*purchase)
Adj'd non-breeding females (op_fem - op_brdr + 0.5*brnd_heifer)
PARTITIONING DEATHS
count of deaths in non-breeders (0.03*Adj'd non-breeders)
count of deaths in breeders (total female deaths - deaths in non-breeders)
DEATHS AS % OF ADJ'D AT RISK
female deaths as % of adj'd females at risk
breeder deaths as % of opening breeders
Year 1
25,505
18,293
11,527
1,698
0
29,311
6,686
864
0
11,101
Year 2
29,311
16,331
10,183
1,248
0
32,799
11,101
3,324
2,666
16,264
Year 3
32,799
17,896
9,194
8,173
0
22,836
16,264
17,272
0
576
Year 4
22,836
18,860
9,238
6,029
0
22,508
576
4,743
0
585
Year 5
22,508
18,920
12,375
3,526
0
23,624
585
5,664
0
735
ALL
132,959
90,300
52,517
20,674
0
131,078
35,212
31,867
2,666
29,261
5,764
5,764
29,571
260
5,092
5,092
33,155
356
4,597
4,597
29,223
6,387
4,619
4,619
21,426
-1,082
6,188
6,188
25,170
1,546
26,259
26,259
138,544
7,466
28,387
10,094
31,857
15,526
35,098
17,202
25,146
6,286
25,602
6,682
146,088
55,788
0.50
0.03
1,674
5,792
5.1%
6.4%
Figure 1: Example spreadsheet showing the data collected from property staff (grey shading)
and the calculated fields
In developing the methodology we have trialled the approach with data from several properties.
In this process a decision was made to not adjust denominators based on sales. Adjustments
were made to allow for increases in animals at risk due to brandings and purchases. Adding half
of the annual total for branded heifers and female purchases was intended to allow for the fact
that additions could occur at any time through the year.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 21
Results
Table 1: Female mortality (deaths per 100 females per year) and 95% confidence interval for
each region and overall
Female mortality
Region
rate
95%CI_low
95%CI_up
QLDsthGulf
4.12
2.29
5.95
QLDnthGulf
11.14
2.65
19.64
Barkly
4.58
3.20
5.96
GKSt
5.86
0.83
10.89
Alice
12.84
3.86
21.81
VRD
7.16
5.61
8.70
KE
6.89
6.09
7.69
KW
3.90
1.57
6.22
Pilb
7.14
3.32
10.97
ALL
6.49
4.85
8.13
The overall female mortality rate may be interpreted as an overall population level estimate of
annual expected female mortalities.
Table 2: Breeder mortality rate by region (breeder deaths per 100 breeders per year)
Mort
Region
Region
rate
95%CI_low
95%CI_up
1
QLD SthGulf
4.40
1.97
6.84
2
QLD NthGulf
17.84
2.42
33.26
3
NT Barkly
5.12
3.25
6.98
4
NT GKSt
11.30
5.73
16.87
5
NT Alice Spr
17.07
3.76
30.39
6
NT VRD
10.13
7.17
13.09
7
WA KE
10.16
8.67
11.64
8
WA KW
5.35
1.80
8.90
9
WA Pilb
10.68
3.40
17.97
ALL
9.06
6.44
11.68
VRRS (Kidman Springs) Field Day Handbook 2012
Page 22
Figure 2: Separate mortality rates estimated for each station, ordered from smallest to
largest. Bars represent 95% confidence intervals. The lower and upper dotted lines
represent the 25th (3%) and 75th percentiles (8%) and the solid line represents the
median (6%) mortality rate. 10% mortality rate represents about the 87 th percentile.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 23
Table 3: Mean mortality rate estimates (deaths per 100 animals per year) derived from
multivariable models for females & breeders.
Variable
Region
Age at last weaning
Supplementary P
Segregation of dry breeders
Age last weaned # P-supplementation
Age wean
<11yrs
<11yrs
<11yrs
11+ yrs
11+ yrs
11+ yrs
Level
QLD S Gulf
Qld N Gulf
NT Barkly
NT GKSt
NT Alice Spr
NT VRD
Kimberley E
Kimberley W
Pilbara
<11 yrs
11+ yrs
No
Whole herd
Part herd
Yes
No
P-suppl
No
Whole herd
Part herd
No
Whole herd
Part herd
Mortality rates
Females
Breeders
5.8
5.5
12.1
19.2
6.1
5.9
3.4
5.9
11.3
15.0
22.8
30.9
12.3
19.1
4.2
5.6
2.8
4.5
4.1
7.0
9.0
11.7
8.9
11.9
9.1
12.4
4.2
5.6
4.1
5.7
8.0
10.9
4.9
9.7
3.9
16.2
8.0
4.7
6.7
12.3
5.7
21.2
12.6
5.4
There are a number of interesting findings from the multivariable modelling exercise.
The mean mortality rate estimates derived from the multivariable model for each region are
different to the univariable or screening results reported earlier. The most likely explanation for
this is that some regions had relatively few properties represented and also when additional
factors were added to the model there were some gaps in the data. For example, NT VRD did not
have properties represented in all combinations of other factors. For these reasons, caution is
urged in interpreting mean mortality rate estimates for regions. Region has been included in the
model to adjust the measured impact of other factors and where it is possible to account for
unmeasured influences at the level of region.
A number of factors were dropped during the model building process because they were found
to be non-significant when included in the multivariable model (age of cows at culling, botulism
vaccination). Again some caution is urged in interpreting these findings. For example there were
only two properties that did not vaccinate for botulism and this may have limited the ability to
assess effects of botulism in a multivariable model.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 24
Similar final models were run with either age at last joining or age at last weaning. The model
with age at last weaning was found to be a better fit to the data than the model with age at last
joining.
It was not possible to consider interactions between regions and other factors in the model
because some levels of explanatory factors were missing in some regions. This is a short coming
of the relatively small sample size. It seems plausible that there could be region interactions. For
example, the effect of dry season segregation or P-supplementation may be more or less
prominent in some regions than in others. This would be consistent with the possibility that
some regions might be more prone to P-deficiency. In addition if one region were considered to
be noticeably more productive country there may be less impact of dry season segregation of
breeders in that region when compared with another region that might represent a more
extreme or challenging environment. Because there were insufficient data these questions were
unable to be addressed in the models.
The only interaction considered for the model was the interaction between age at last weaning
and P-supplementation to test whether cow age could have an impact on the influence of Psupplementation.
The findings from that interaction are suggestive of a major benefit for P-supplementation in
older cows in particular.
The female mortality rates estimated for the combinations of age at last weaning and Psupplementation suggest that there is less impact for P in younger cows. The important
comparison is the very large increase in female mortality rate in properties where cows are older
at last weaning and do not supplement with P (16.2 deaths per 100 females per year). In
contrast, properties where cows were older at last weaning and that did supplement part of the
herd with P, were found to have a female mortality rate of 4.7 deaths per 100 females per year.
This death rate was not different to the mortality rates reported for properties that last weaned
their cows at a younger age. These findings suggest that supplementing older cows with P may
help to avoid the age-associated increase in female mortality rate.
It is not clear why the whole herd P-supplementation might be associated with an elevated
female mortality rate as indicated in the previous table. There may be some management
differences between properties that supplement whole herds vs those that supplement just part
of the herd.
Botulism vaccination is considered likely to have an important potential impact on animal health
and survival. It was not retained in the final model but this was considered to be at least partly
because almost all properties vaccinated, providing less opportunity to assess the effects of this
variable in a multivariable model.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 25
An attempt was also made to compare the relative importance of the three factors in the final
model (age at last weaning, segregation of dry breeders and P-supplementation), using
population attributable fractions (PAF). PAF is defined as the proportional reduction in average
mortality risk that would be achieved by eliminating the effects of one particular factor, while
leaving the effects of other risk factors unchanged.
PAF (%)
PAF
26
24
22
20
18
16
14
12
10
8
6
4
2
0
age_LW
P_suppl
Br_segre
Region_Barkly
Factor
Figure 3: Population attributable fractions (PAF) for each of the four factors in the final model:
age at last weaning, P-supplementation, breeder segregation when dry and region.
Interpretation of the PAF values requires an understanding of the reference or baseline level.
With respect to age at last weaning, the reference level was the lower age group (<11 yrs). The
exposure level of interest was the older age group (11+ yrs). If the exposure could be completely
eliminated (meaning that if all properties were to adjust their weaning practices such that the
age at last weaning on all properties was <11 yrs, then the expected impact would be a 12%
reduction in female mortality.
In contrast, if all properties adopted P-supplementation at a level equivalent to the effect seen
for part herd supplementation, then the effect would be expected to result in a 20% decline in
female mortality.
If all properties were to implement segregation of breeders during the dry (presumably
accompanied by other management decisions such as better access to feed or targetted group
supplementation), then the expected effect would be to reduce female mortality by 22%.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 26
There was no immediately identifiable reference level for region so the approach used was to
assume that all properties implemented changes such that their performance was made
equivalent to the NT Barkly performance. This is basically using an arbitrary baseline level to
assess the impact on female mortality if all of the effects associated with region were removed.
The result (reduction in female mortality of more than 24%) indicates that factors operating at
the regional level (other than the 3 factors included in the model) continue to provide the most
important contribution to female mortality. This is interpreted as a simple measure of the
relative importance of regional effects on female mortality.
These findings suggest that the two most important interventions that properties may wish to
consider are related to P-supplementation and management of breeders during the dry. Earlier
culling of cows (as represented by age at last weaning) is important but less so. Other
unmeasured regional effects may also be important and may include things that potentially can
be corrected but were not measured in the current project.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 27
Expected growth results from HGPs at the Hayfield PDS
Trisha Cowley – Pastoral Production Officer – Katherine – trisha.cowley@nt.gov.au
Do HGPs work? Well, despite being a doubter before initiating this trial, my answer now is “Is
the Pope Catholic”!! The Hayfield HGP Producer Demonstration Site (PDS) has 2 years of data
that shows that HGPs do indeed work. This further supports the bulk of research on HGP use in
northern Australia which has shown that when used properly HGPs increase growth rates
significantly, in the order of 10-15% in grassfed cattle. This article will look at the growth results
from the Hayfield PDS and compare the cost benefit of the different strategies.
What was tested?
Four different HGP strategies were compared (the italics indicate the abbreviations for each
treatment):

2 x 200 day Compudose® implant - inserted at weaning in round 1 and again at the end
of the dry/start of the wet season – 2 x 200D
 200 day Compudose® inserted at the end of the dry/start of the wet season – Wet
season 200D
 400 day Compudose® inserted at weaning in round 1 – 400D
 No HGP
The trial was repeated, with a 2010 and a 2011 group of weaners undergoing the same
treatments during their first year post weaning. Steers were weighed at weaning, at the end of
the dry season and after the wet season. Weight gain during these periods was compared
between the different HGP strategies.
NB: The 2x200D was not in effect a true 2x200D as the first implant was only in for 100-160 days
before the second HGP was implanted – due to practical constraints.
Why test these strategies?
Firstly we wanted to get some local data on growth responses to HGPs – what could we
realistically expect? Thus we tested the most common strategy (400D at weaning). Secondly,
we know that the best response to HGPs is achieved when animals are growing compared to just
maintaining or losing weight. Since weaners typically maintain or lose a little weight during the
dry season in the NT, were Hayfield better off just putting a 200D in over the wet rather than
“wasting” hormone during the dry season? Thirdly, another key principle of HGP use is that
animals under continual positive growth show better total liveweight response to the use of
more, shorter acting implants than the use of fewer longer acting HGPs. Hayfield can have green
feed well into the dry season in their weaner and steer paddocks and they routinely shift their
weaners from a dry season to a wet season paddock. Hence there was an opportunity to test a
2x200D strategy – would this be superior to the 400D? A final key principle of HGP use is the
“whole of life” principle, which holds that once a HGP program is started it should be continued
until slaughter/sale for the best growth response. This was partially explored by measuring the
growth of steers when their HGP had finished its active life and again 1 year later – would the
growth response still be there?
VRRS (Kidman Springs) Field Day Handbook 2012
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Growth results
The 2010 and 2011 seasons were very different at Hayfield, and the weaner groups differed
significantly in weaning weight. Table 1 below details the weight gains over the different
seasons for 2010 and 2011.
Table 1: Sample size, weaning weight and average growth of the 2010 and 2011 weaners
Year
N
Av weaning
weight (kg)
Av. dry season
gain (kg)
Av wet season
gain (kg)
Av annual gain
(kg)
2010
470
197
-3
74
70
2011
494
232
-6
109
103
HGPs significantly improved liveweight gain
Across all growth periods (dry season, wet season and annual), HGPs significantly increased
growth compared to the group without HGPs. However, all HGP strategies resulted in similar
growth responses (i.e. none were superior in terms of liveweight gain).
Weight advantage over No HGP (kg)
20
15
10
400D
2x200D
Wet season 200D
5
0
2010
2011
Dry advantage
2010
2011
Wet advantage
2010
2011
Annual advantage
-5
Figure 1: Liveweight gain advantages of HGP strategies by season and year
VRRS (Kidman Springs) Field Day Handbook 2012
Page 29
While there were slight differences between the strategies, these were not significant and so we
have no confidence that they reflect true differences. Annual growth advantages were between
12.5% - 18% over the two years, confirming the assertion that you can get a 10-15% growth
advantage.
But were all strategies as profitable?
A simple cost-benefit analysis revealed that while the HGP strategies equally improved
liveweight gain, they were not equally profitable. The following was assumed when doing the
cost-benefit:



As the 400D is put in at weaning, no extra mustering costs are required. However, as
the 2x200D and Wet season 200D require an extra muster, this cost has been added, at
$10/head (based on the average mustering cost in the 2010 Pastoral Survey)
Cost of HGPs: 400D = $6.80/head, 2x200D = $7.60/head, Wet Season 200D = $3.80/head
Total $ weight gain = liveweight advantage X $1.80/kg
30.00
25.00
Return per head ($)
20.00
15.00
400D
2x200D
Wet season 200D
10.00
5.00
0.00
2010
2011
Average
-5.00
Figure 2: Return per head of each HGP strategy for each steer mob
VRRS (Kidman Springs) Field Day Handbook 2012
Page 30
The raw weight data was used to calculate these so there were small weight gain differences
between each strategy despite there being no significant difference. To be conservative you
could assume the same weight gain for each strategy. However, the 400D still wins out by a long
way. In order for the Wet season 200D to make the same return as the 400D, mustering costs
would have to equal $3/head (which is possible to achieve, especially if trapping on waters or
not using helicopters!). The 2x200D could only equal the return of the 400D if the second
muster had to occur for other reasons, therefore no extra mustering costs were added to the
cost-benefit analysis.
What about 2 years after weaning?
About 60% of the 2010 steers were less than 280kg after one wet season. Hayfield targets
heavier live export markets (eg. Egypt) as well as selling feeder steers and so hold lighter steers
over another wet. Theoretically the lighter steers should have been re-implanted to maximise
the growth response (i.e. whole of life principle), but in this case they were not. In July 2012,
354 steers were reweighed. By this time the 400D steers had been without an active HGP for
318 days while the 2x200D and Wet Season 200D steers had been without one for 383 days.
Not only had the initial weight advantage measured in June 2010 been maintained, but
unexpectedly, it had more than doubled. There was no significant difference in weight gain
between the 3 HGP groups, but all were still significantly higher than the control group.
35
30
25
20
400D
2x200D
15
Wet Season 200D
10
5
0
Total growth (kg)
Return per head ($)
Figure 3: Total growth advantage and return per head of HGP strategies
This data makes HGPs appear an even better deal! (It must be noted that a smaller number of
animals were measured (only about 30 head per treatment) and we have not replicated it.)
What remains unknown is whether re-implanting the carry-over steers would have resulted in an
even greater return (as the whole of life principle suggests).
VRRS (Kidman Springs) Field Day Handbook 2012
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HGP loss can be an issue
The data that DoR has collected on 5 NT properties indicate that HGP loss does occur and can be
anywhere between 1.5% - 52%. It is normal to expect some loss. In this trial, loss varied
between HGP strategies and across years. In 2010 there was 7% loss in the 400D and Wet
Season 200D groups. However in the 2x200D group 3% lost both HGPs and 19% lost 1. In 2011,
the 400D group lost 9% and the 2x200D group lost 8% of the first HGP implanted. However,
there was high loss in the groups implanted at the end of the dry season. The Wet season 200D
lost 25% of implants, and the 2x200D lost 38% of the second implant. It is unknown why this
loss was so high. It rained for about a week following implanting so this may have led to higher
losses.
HGP implantation training – it’s easy and it’s worth it!!
Implant loss can be minimised through correct implanting techniques and good hygiene.
Implantation training is offered by DoR, Elanco and Coopers for free. Is it worth it – YES!! Based
on the assumptions used above for the cost-benefit calculations, for every steer that loses a HGP
it’s an opportunity cost of $29 for 400D, $43.40 for 2x200D (assuming they lose both) and $40
for a Wet season 200D!!
VRRS (Kidman Springs) Field Day Handbook 2012
Page 32
Key learnings

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







HGPs can cost-effectively increase growth under NT conditions.
The real pay out of the HGP happened over the wet, but there was still some benefit
over the dry
The dry season growth advantage alone paid for the cost of the implant
400D, 2x200D and Wet Season 200D were equally effective in increasing liveweight gain.
400D was the most cost-effective strategy.
Mustering for the sake of implanting HGPs needs to be carefully considered as it can
significantly reduce the cost-effectiveness of the HGP.
The true cost-effectiveness will depend on your mustering costs and whether you do
have to factor in the end of dry season muster as a cost – if it is happening anyway and
implanting is a bonus, then Wet season 200D is likely to be the most cost effective
strategy as the only difference is the cost of the implant which is slightly cheaper.
Consider the effect of HGPs when determining if steers will blow the 350kg weight limit
over the wet
Staff training in correct implantation techniques is essential so contact your local rep.
Some loss is still to be expected.
It appears that higher loss can occur if putting in a second implant but the causes remain
unclear.
Weight advantages were sustained after the end of the implants’ functional life.
I would like to gratefully acknowledge MLA for funding the PDS and Elanco for donating the
HGPs. A huge thanks goes to the Dyers for lending their cattle and investing mustering costs
and man-hours into the trial. Particular thanks goes to Craig & Caroline Butcher, Lisa Dyer
and Brad Inglis who have made it all so easy, been so helpful, and who’ve shared a lot of
laughs along the way!
VRRS (Kidman Springs) Field Day Handbook 2012
Page 33
Weaner Management in northern beef herds
Kieren McCosker – Beef Research Officer – Katherine – Kieren.mccosker@nt.gov.au
Weaning is a well-established practice in northern Australia. However, there a number of views
on how it should be done. Meat and Livestock Australia recently supported the input from
research and extension staff across Northern Territory, Queensland and Western Australia to
review the current knowledge about weaning and weaner management and produce a manual
for producers.
The emphasis in this book is two-fold: to describe best management practice for feeding and
educating weaners; and to promote weaning of young light calves under difficult conditions to
reduce mortality and improve fertility in the breeders.
Copies are available at the field day or:
Digital copies can be downloaded at:
http://www.mla.com.au/Publications-tools-and-events/Publication-details?pubid=5884
Hard copies can be ordered by calling the MLA membership services hotline on 1800 675 717 or
email publications@mla.com.au - or from the Department of Resources - Email:
technical.publications@nt.gov.au
VRRS (Kidman Springs) Field Day Handbook 2012
Page 34
Key messages for managing weaning and weaners:
Some general principles can be applied to weaning strategies and weaner management.
















Calves are taken from their mothers mainly for the benefit of the cow.
When the need to produce milk is stopped, the cow's nutrient requirement is reduced,
allowing her to regain condition.
When the need to produce milk is stopped, it is equivalent to feeding the cow with 2kg
of grain or 3kg of fortified molasses each day.
Lighter stocking in breeder paddocks maximises the opportunity for the cows to
maintain good body condition.
The cow needs to have a body condition score of 3.5 or higher at calving to maximise the
chance of getting pregnant again while rearing her calf.
A cow must get pregnant within 75 days of calving to produce a calf every year.
Weaning to maintain the cow's body condition will improve reconception for the next
mating. It is too late for the current reconception.
With seasonal mating, calves are normally weaned at four to eight months of age
between April and June.
With year-round mating, calves are at a wide range of ages at the first muster (April–
June); weaning all calves over 100kg allows the cows to recover body condition and
better survive the dry season.
If the wet season fails, all calves can be weaned younger under both seasonal and
continuous mating systems.
Hay is the main feed for weaners in the yard. Good quality hay must always be available
from the first day of weaning.
Calves weaned under 150kg should gain at least 100g per day, and will need
supplements of highly digestible protein and energy if pasture quality is insufficient.
Heifer calves retained as breeders should be fed to gain at least 100g per day over the
dry season after weaning.
Weaning is the time for educating young animals to set them up for ease of handling
throughout their lives.
Weaner education includes being worked calmly through the yards and being tailed out
from the yards to the weaner paddock and back for five to seven days.
Weaner paddocks should be rested over the year to accumulate a body of good grass
and herbage; they should not be used as holding paddocks for sale or sick stock, or for
the working horses.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 35
Validation and demonstration of a diagnostic tool for
phosphorus status of beef cattle in northern Australia
Casey Collier – Pastoral Technical Officer – Tennant Creek – casey.collier@nt.gov.au
Background
Large areas of grazing land in northern Australia have Phosphorus (P) deficient soils, and hence
forages, resulting in low P intake by cattle. A P deficiency in breeding and growing cattle can
have adverse effects on both reproduction and growth respectively. In P deficient areas,
supplementation of growing cattle with P in the wet season has been recommended, as P is the
first limiting nutrient at this time and a response to P will occur. Despite the potential benefits of
P supplementation in P deficient country, P supplement sales across northern Australia are
lower than might be expected. Meat and Livestock Australia identified several possible reasons
for the low adoption of P supplementation in northern Australia including the lack of a reliable
diagnostic test to determine the P status of cattle and issues associated with distribution and
intake of P supplements in the wet season.
This project consists of two experiments which will,
1. validate the ratio of faecal P to dietary N (or digestibility) as a diagnostic tool to
determine P status of animals,
2. demonstrate the response of growing animals to dietary P, and
3. investigate whether producers can supplement breeders in the dry season in order to
build up P in the skeleton, which can then be mobilised when lactating in the wet
season, with the effects on reproductive performance monitored. If there is potential for
a move from wet to dry season supplementation, this may facilitate greater uptake of P
supplementation in areas of P deficiency.
Experiment 1: Liveweight gain and faecal P of growing animals in response to increasing
dietary P content
A pen experiment was conducted at The University of Queensland, Gatton campus, QLD. Thirsty
steers (225 kg liveweight) were maintained in individual pens and fed one of five diets (11%
crude protein and 60% digestibility) with increasing P content (P-1, 0.09% P; P-2 0.13% P; P-3
0.17% P; P-4 0.21% P; P-5 0.24% P) over 7 months (Phase 1). Liveweight, hip height, feed intake
faecal P: dietary N, plasma P, plasma osteocalcin and change in bone P, density and thickness
measured throughout. At the end of Phase 1, all animals were then fed the P-5 diet for 3 months
(Phase 2), with the same parameters measured. Steers fed the low P diet had lower feed intake
and liveweight gain than steers fed the high P diet during Phase 1 but had greater liveweight
gain when fed the same high P diet during Phase 2 (Figure 1).
VRRS (Kidman Springs) Field Day Handbook 2012
Page 36
Figure 1: Liveweight of steers fed varying levels of P over the two phases of the experiment
Experiment 2: Wet and Dry season feeding of cows and growing steers with P under
commercial conditions
A field experiment is in progress at Brunchilly Station (S Kidman & Co.), Tennant Creek, NT. The
main objectives of the field experiment are to determine the response of breeders to different P
supplementation strategies on an extensive northern property, to investigate the carryover
effects of dry season P supplementation on breeder P reserves and subsequent fertility, and
determine if dry season P supplementation is a potential strategy to provide P supplements to
breeders in P deficient country.
580 breeding cows (calving Oct – April) and 80 growing steers are grazing a 67km2 paddock with
two watering points, each equipped with an autodrafter and walk over weighing system.
Animals are being drafted one of two ways, either to +P or -P supplement in the wet and dry
season. At the end of the wet season half of each treatment group (+ or – P) was swapped
resulting in four treatment groups;
1.
2.
3.
4.
+P in the wet / +P in the dry
+P in the wet / -P in the dry
-P in the wet / +P in the dry
-P in the wet / -P in the dry
All animals have ad libitum access to a loose lick supplement, with the only difference between
the +P and -P supplements been the inclusion of a P source (Table 1). Animals are individually
identified with unique management and NLIS tags; the NLIS tag is scanned and recorded as the
animal walks though the autodrafter and over the walk-over-weighing facility, providing
liveweight and accuracy of draft information. The use of the autodrafter allows the different
treatment groups to be grazed in a single paddock, eliminating variation associated with
paddock effects. Data collected throughout the duration of the trial includes supplement intake
(averaged over the treatment group), liveweight (taken as each animal enters the water yard via
the walk-over weighing system and at musters), body condition score and pregnancy testing and
VRRS (Kidman Springs) Field Day Handbook 2012
Page 37
foetal aging of all breeders (conducted in August each year). In addition blood, bone and faecal
samples are collected from a sub group within each treatment.
Animals require some training to use auto-drafters and the animals were adapted to the
autodrafters during the 2011 dry season with experimental supplementation commencing at the
commencement of the 2011/12 wet season. The trial is due for completion at the start of the
2013 dry season, with final pregnancy testing to be conducted in August 2013.
Table 1. Ingredients (%) of wet and dry season supplements to be used in the field experiment.
Ingredient
Dry season
Wet season
+P
-P
+P
-P
Cottonseed meal
10
10
0
0
Limestone
10
10
0
0
Biofos
30
0
50
0
Urea
25
25
0
0
Salt
14.5
44.5
44.5
94.5
Gran-am
10
10
0
0
Premix
0.5
0.5
0.5
0.5
EC feed
0
0
5
5
The Phosphorus project is funded by Meat and Livestock Australia and is been conducted by
the Northern Territory Department of Resources in collaboration with The University of
Queensland and Precision Pastoral, with sponsorship by Ridley Agri-Products, The Mosaic
Company and Allflex.
VRRS (Kidman Springs) Field Day Handbook 2012
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Factors affecting liveweight gain in north Australian beef
herds
Nigel Perkins - AusVet Animal Health Services – nigel@ausvet.com.au
Sarah Streeter, Neil McDonald –Pastoral Production – Katherine
Introduction
This project was motivated by interest in improving liveweight gain in young growing beef cattle
in extensive, northern pastoral areas of Australia. The project was designed to investigate
variation in liveweight gain, to identify reasons for the variation and potentially identify options
for improving overall growth by improving the lower end of the performance spectrum.
The project, which was funded by Meat and Livestock Australia, involved multiple components
managed by Sarah Streeter with assistance from a number of other people. The main
components were analyses of historical datasets contributed by the Beef CRC and two northern
pastoral properties, and a large-scale longitudinal study involving 11 properties sourced from
different regions within the NT and running from 2008 to 2011. The cooperation of these
properties and their staff is gratefully acknowledged.
This presentation will cover selected aspects of the findings of this project. The final report from
this project is being finished currently and should be released later this year.
Historical datasets
Historical data on growth in animals post weaning was sourced from the Beef CRC and from two
northern pastoral properties. The Beef CRC data used was restricted to animals that were grown
post-weaning on pasture in northern QLD. Additional data were sourced from Douglas Daly
Research Farm (DDRF) and from one commercial enterprise (CE) in the NT. Analyses focused on
weaning weight and growth post weaning.
The single biggest driver of liveweight at weaning was the age of the animal at weaning. Age
accounted for 40-59% of the total variance in weaning weight. The CRC data was drawn from
animals raised pre-weaning on a large number of different properties and the property of origin
accounted for almost 30% of variance in weaning weight. The DDRF and CE data were from
multiple years but from the same property and as a result there were important effects of
season and year of birth (accounting for up to 13% of variance in weaning weight). The larger
contribution of age from the DDRF and CE data is likely to be because the effects of property
level variance have been eliminated. These findings are consistent with earlier reports by Tim
Schatz and others that have indicated age at weaning may account for as much as 70-80% of
variance in weaning weight in a given year from a given property. Incorporating multiple
explanatory factors (age, sex, year of birth, season of weaning) provided a multivariable model
that could account for between 60-70% of total variance in weaning weight.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 39
When analysing weight gain (kg/hd/day) post weaning, the biggest driver in all datasets were
variables measuring the effect of between year variability, accounting for between 25-99% of
variability in growth. Other factors tended to account for much smaller proportions of variance.
As an example, sire identity accounted for 1 to 21% of variation in growth. The findings suggest
that year to year variability in nutritional quality and quantity may swamp the impact of other
factors.
Commercial study
Data were collected from a total of 11 commercial properties located in the northern regions of
the NT. An attempt was made to align the study activities with routine commercial operations
but, additional mustering and handling was occasionally required. Study animals were enrolled
at a first-round weaning muster and monitored for approximately 12 to 15 months (Figure 1).
Animals were generally accessed on 4 occasions; Weaning, post-weaning, pre-wet and postwet/early dry. A very wide range of data and information were collected on property level
factors and animal level factors.
Figure 4: Sequence of observations and major outcomes of interest (ADG_DS, ADG_WS and
ADG_AN).
It is not possible to describe all of the findings in a brief summative article. This article will
concentrate on a couple of aspects of the results.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 40
Weight vs height
There was considerable interest in the potential for assessing growth as growth in skeletal
structure or frame (hip height) and growth in weight. Animals were classified into four groups
based on measurements at weaning:




short and light
short and heavy
tall and light
tall and heavy
There was some evidence for differential growth but this seemed to be expressed differently in
different seasons. Animals that were recorded as having a below average weaning-weight
recorded a higher average daily gain over the dry season than above average weaning weight
animals. . Similarly, shorter animals at the time of weaning were recorded as having the highest
height increase than tall animals at weaning. However, the highest dry season average daily gain
in any one category was in the light/tall animals and the lowest dry season average daily gain
was in the short/heavy animals. Overall, the dry season growth was relatively small for most
animals and occasionally negative.
There was little difference between weight:height category and wet season growth with all
animals achieving relatively high wet season average daily gain values (>0.4 kg/day). The highest
wet season average daily gain was seen in the heavy/tall animals at weaning. Generally, wet
season average daily gain increased with increasing weaning weight (larger weaners had a higher
wet season average daily gain) but that there was a penalty associated with the heaviest
weaners – as weaning weight increased to about 250kg or more, wet season average daily gain
tended to decline slightly.
Animals that were heavier at weaning tended to also be heavier at the post-wet muster. Though,
the difference between the heavier (upper 50%) and lighter (lower 50% based on body weight)
had reduced slightly from weaning to post-wet muster (from a difference of 45kg to a difference
of 37kg). Taller animals tended to be heavier than shorter animals and this advantage increases
as animals aged. Heavy /tall weaners were recorded as performing the best over the following
year, followed by heavy/short weaners. The animals recorded as having the lightest final weight
were the light/short weaners. The light/tall weaners were heavier at the post-wet muster than
the light/short weaners.
Flight speed
Flight speed (speed animal travels from a crush) was considered as an indicator of animal
temperament. Consistent with previous research, flight speed was found to decrease over time
due to animals becoming accustomed to being handled in the crush. Animals with higher flight
speeds were found to have lower average daily gains over the wet season and annually.
Therefore, selecting for better temperament would possibly result in improvements in weight
gain. However, the associations were small and the achievements in weight gain may be
relatively small.
VRRS (Kidman Springs) Field Day Handbook 2012
Page 41
HGP
Hormonal growth promotants were used on almost all properties but there was very little
consistency between properties in how they were used. Animals received either one or more
implants and implants were administered to animals at varying times (as calves, branding,
weaning or at later musters). HGP administration was generally associated with a significant
improvement in weight gain and administration of HGP to calves appeared to produce a higher
wet season and annual average daily gains compared with administration at weaning.
In an unexpected finding, one property was identified as having a high rate of loss of HGP
implants (56% of animals were found to have lost their implants). Losses were associated mostly
with infection and abscessation at the implant site. With the exception of this one property
other properties experienced loss rate ranging from 2 to 12%. Loss of implants was associated
with a reduced weight gain and represents a significant cost. Implant loss appears preventable
through training and use of best practice technique.
Effect of sire
An attempt was made to identify sires for those animals that were enrolled in the study. This
was done by performing DNA sequencing on hair samples from sires and enrolled weaners.
Analysis was restricted to those properties where >50% of animals were able to be matched to a
sire to try and get larger sample sizes. Analyses were limited due to each sire only being used on
one property and usually only sired a small number of progeny in the study. Models using
weaning weight and annual average daily gain as outcomes indicated that sire accounted for
between 0 and 30% of unexplained variance. The results suggest that there may be years where
environmental conditions are such that genetic gains are not realised. However, in other years
the potential gain resulting from using genetic selection in northern beef herds is possibly similar
to that in southern beef herds.
Other factors
The impacts of a number of management procedures were investigated in this study, such as
castration, dehorning, disease, parasites and various other factors. There was little evidence of
management procedures having a major impact on weight gain post weaning. These findings
tend to support a hypothesis that, whilst their acute or chronic impact might be moderate to
high the effects associated with these procedures do not persist for extended periods of time.
VRRS (Kidman Springs) Field Day Handbook 2012
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The Selected Brahman Project
Renee Rippon – Beef Research Officer – VRD – renee.golding@nt.gov.au
Tim Schatz – Principal Pastoral Production Officer – Darwin – tim.schatz@nt.gov.au
Project Aim:
To investigate the gains in productivity that can be made through selection for
fertility in a Brahman herd
NT DoR has a Brahman herd that has been selected for fertility since 1994. The herd joined
BREEDPLAN in 1994 (incorporating performance data back to 1986). The herd has been located
at Kidman Springs in the VRD since 2002 (previously Douglas Daly).
Selection involved:
Females
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Cows were culled if they did not raise a calf each year (except 1st calf heifers)
Heifers mated as yearlings for a period of three months.
Heifers must wean 2 calves in 3 years following yearling mating. In years with high
pregnancy rates can be even stricter – higher selection pressure.
Bull selection
AI sires (used in heifers) - Selected using a selection index that places high importance on fertility
EBVs. Only chosen from herds known to cull non pregnant cows.
Bulls bred within the herd were selected for use as yearlings on the basis of a selection index
that placed emphasis on:
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large scrotal size as yearlings
high 400 day weight
high percentages of normal sperm (as yearlings)
low age of their dam at calving and high dam “never miss a calf” scores.
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Result:
Significant progress has been made through selection for fertility.
An experiment was conducted at the Douglas Daly Research Farm to test whether selection had
been successful in improving heifer fertility: Compared the pregnancy rates from yearling mating
in;
Heifers from the Selected Brahman herd (SEL)
v.
Heifers sourced from NT commercial properties (COM)
Three year groups of heifers were used. Each year about 100 1st round weaner heifers were
purchased from a (different) commercial property and compared to heifers from the SEL herd
(avg. number = 31) in the same weight range (220-300kg).
In each year the pregnancy rate from yearling mating was significantly higher in SEL heifers. On
average pregnancy rates were 35% higher in heifers from the SEL herd.
When heifers don’t conceive from yearling mating it is likely to be because they have not
reached puberty by the end of the mating period. SEL heifers are earlier maturing than
commercial heifers (Beef CRC found average age at puberty for Brahman heifers = 750 days).
A number of studies have shown that lower heifer age at puberty is associated with improved
fertility at later ages. The higher fertility in the older cows in this herd has been confirmed by
results from breeder herds at VRRS. Pregnancy rates in lactating cows at WR1 were 37% higher
on average than in an unselected herd between 2004 and 2009 (Table 1).
Figure 5. Proportion of lactating cows pregnant at WR1, Selected Brahmans (SEL) v.
Commercial Brahmans (CON).
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Figure 6. Comparison of the EBV values for days to calving, SEL v. Avg.
Figure 7b. Comparison of the EBV values for scrotal size, SEL v. Avg.
Progress made by selection is also being seen in comparing the EBVs for fertility traits between
the SEL herd and the Brahman breed average.
Genetics from the Selected Brahman herd are available to industry through bull and semen
sales.
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Managing Woody Vegetation Using Fire in the Victoria
River District
Dionne Walsh – Rangeland Program Coordinator – Darwin – dionne.walsh@nt.gov.au
Introduction
Woody vegetation thickening has been widely observed across northern Australia since
European settlement. In the VRD this has been documented in the book “Slower than the Eye
Can See” which contains many photographic examples (Lewis 2002).
If left unmanaged, woody vegetation thickening can lead to declines in pasture condition, feed
production, animal performance, mustering efficiency and profitability (Dyer & Stafford Smith
2003). The most cost effective method of managing the problem in northern Australia is via
burning (Dyer & Stafford Smith 2003). A long-term burning trial at Kidman Springs aims to
provide recommendations to industry about the use of fire to control woody vegetation
thickening.
Local Research, Local Knowledge
The ‘Shruburn’ trial was established on Kidman Springs in 1993 to answer the following
questions:



When is the best time of the year to burn?
How often does country need to be burnt?
Do different land types need different burning management?
Two sites were established – one on a ‘red soil’ site in Conkerberry paddock and one on a ‘black
soil’ site in Rosewood West paddock. The red soil site is an open eucalypt woodland with a
pasture layer dominated by black speargrass (Heteropogon contortus), bottlewashers
(Enneapogon spp.) and curly bluegrass (Dichanthium fecundum). The black soil site is a
grassland-shrubland dominated by perennial grasses such as ribbon grass (Chrysopogon fallax),
curly bluegrass (Dichanthium fecundum), silky browntop (Eulalia aurea) and feathertop wire
grass (Aristida latifolia). The major tree species on the black soil site are rosewood and bauhinia.
The trial plots have been designed to compare the frequency of burning (none, every 2, 4 or 6
years) and the season of burning (“early ” – June or “late” – October).
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Findings to Date & Current Recommendations
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Early burns do reduce tree canopy cover but late burns have a bigger impact.
Burning every two years or every four years is more effective than burning every six
years for managing woody vegetation.
Late burns every 4 years achieve a good balance between managing woody thickening
and managing the feed supply.
But late burns are riskier in terms of control and interventions may be required to
ensure enough fuel at that time of year (e.g. stocking rate management or pasture
spelling). They also generate more greenhouse gas emissions than early burns.
Stocking rate management and rainfall have more influence on long term pasture
condition than the burning regimes investigated in this trial.
To prevent animals from overgrazing small burnt areas, it is recommended that at least a
quarter of the paddock is burnt at a time.
Regular burning of pastures dominated by short-lived (annual) pastures is not
recommended due to the risk of land degradation.
Due to lower rainfall, greater care needs to be taken when considering burning in the
southern VRD.
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Aerial Photo of the Red Soil Site June 2011
Aerial Photo of the Black Soil Site June 2011
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Acknowledgements
Much of the information in this article has been sourced from recent publications by Trisha
Cowley. The following people have made major contributions to the trial over the past 19 years:
Rodd Dyer, Robyn Cowley, Trisha Cowley, Caz Pettit, Kidman Springs managers and staff, Mark
Hearnden and agency field staff.
References
Dyer R.M., Stafford Smith M. (2003). Ecological and economic assessment of prescribed burning
impacts in semi-arid pastoral lands of northern Australia. International Journal of Wildland Fire
12, 403-413.
Lewis, D. (2002). ‘Slower than the eye can see’. Tropical Savannas Cooperative Research Centre,
Darwin.
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~ Notes ~
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~ Notes ~
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~ Notes ~
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