Dr. Mary Drewnoski
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US agriculture production oriented

More is better! Right?

Focus on making profitable decisions
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Increasing profit
◦ Increase the price we get for product
◦ Increase amount of product produced
◦ Decrease production costs
In cow/calf and stocker programs we typically
strive to utilize forages as the major source of
nutrients
 Have to manage the plant and the animal

Use supplements to
◦ Correct nutritional deficiencies
◦ Conserve forage/increase stocking rate
◦ Increase overall plane of nutrition
The
green leaf
It is also the primary source of feed!!
High
Top growth
Low
TNC in tap root

Both the plant and animal need to be
considered

Think lbs per acre not per animal
◦ Timing of grazing
 Need to allow the plant to restore its energy reserves
◦ Intensity of grazing
 How much of the leaf is removed/left
 Take half leave half

The ultimate measure of forage quality is animal performance

Animal performance is determined by
◦
◦
◦
◦
◦
feed availability
feed nutrient content
Intake
extent of digestion
metabolism of the feed digested


Availability and intake most often determine animal
performance
◦ A cow never produced milk or a steer never grew on feed that it
didn’t eat!
Forage
height
Does it matter?
500 lbs/acre
12 acres = 6000 lbs allowance
for the herd
1500 lbs/acre
4 acres = 6000 lbs allowance
for the herd
2500 lbs/acre
2.4 acres = 6000 lbs allowance
for the herd
Grazing Time = 8 to 10 hrs. per day
two periods before dusk and after dawn
Rumination Time = 6 to 8 hrs. per day regurgites
forage, chews it, mixes with saliva and swallows it
Bites per Day = 40,000
Gain (lbs/ewe/day)
0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
2
6-10”-2500 lbs/A
4-6”-1500 lbs/A
1-2”-500 lbs/A
4
6
8
10
12
Pasture Allowance (lbs DM/ewe/day)
Intake, g/min
7
6
5
4
3
2
1
0
Bite size, g
Bite number/minute
0
2
4
6
8
Tiller length, in.
10
12
14
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Animal performance depends on intake of the
forage.
Overgrazed pastures/range are generally the
result of over stocking, which, in turn,
diminishes the ability of the animal to select
plant species or plant parts of higher nutritive
value.
Consequently in overgrazed pastures/range,
forage intake declines.
• Selectivity
 Animals will select the best forage first
 They prefer young, green forage
 They will avoid areas that have been walked on, urinated
on and areas around dung
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
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Intake increases if new grass is given daily
forage availability (allowance)
gain per animal & per acre
Milk per cow fluctuates with rotational grazing
Daily Milk/cow, lbs
35
33
31
29
Pad 1
8 days
Pad 2
8 days
Pad 3
9 days
Pad 4
9 days
Available pasture grazed from 10” to 3” over 8-9 days.
To “talk” about Forage Quality we need to understand Fiber
1.
2.
3.
4.
Fiber is the “cell wall” portion of the plant cell that
holds the plant up
Fiber is food for the rumen microbes and helps the
cow maintain rumen health (cud chewing; saliva,
higher rumen pH)
As plants mature, the ratio of cell wall to cell content
goes up and the cell wall becomes less digestible
There is only so much fiber the cow can consume (only
so much space in the rumen)


The more mature and fibrous (lower in
quality) a forage, the longer it takes to
be digested and the less an animal will
consume
Stage of growth at harvest or grazing
has more to do with nutritive value
than most anything else.
•Digestibility and yield are dependent on stage
of growth
•As plant matures digestibility decreases and
yield increases (to a point)
Animal Requirements
Grazing animals will usually eat between 2-3% of body wt
Animal class
%TDN
%CP
Growing steer 450 lb (1.5 lbs/day)
65
11-13
Growing steer 650 lb (gaining 1.7
lbs/day)
68
10-11
Lactating beef cow
60
10-12
Dry beef cow
50
7-8
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
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Balancing dietary protein and energy in
supplements is important to ensure
successful response to supplementation
The nutrient that is most limiting or deficient
should be supplied first
Key to have an idea of the quality of the
forage that is being grazed/fed and adjust
the supplement accordingly

Positive associative effects
◦ Increase ruminal N (when N is limiting digestion)

Negative associative effects
◦ Decrease ruminal pH
◦ Decrease ruminal available N

The ability to infrequently feed supplements
depends on supplement characteristics
◦ Protein and non-structural carbohydrate (starch)
content


When feeding protein supplement can feed 3
times a week with little effect on performance
When feeding energy the affects are more
variable
◦ High NSC feeds may cause digestive upsets
◦ More likely to cause increased substitution than
feeding daily
◦ If protein in the forage or supplement is high then
can supplement 3X a week with less potential for
decreased performance


To maximize intake of forage feeding rates
should be about 0.2 to 0.5 % body weight
Using energy supplements highly digestible
fiber will reduce likelihood of substitution
and negative impacts on forage digestibility
when fed at high rates



If protein is deficient, supplements should be
evaluated based on cost per pound of
protein.
Forage supply is limited or energy is
deficient, supplements should be evaluated
based on cost per pound of total digestible
nutrients (TDN; energy).
Prices are seasonal and vary year to year so
you will need to pencil this out
Matching Animal Needs to Pasture Quality
Energy
85
Cool season grasses
80
75
70
1200 lb cow* nursing calf or
65 500 lb steer gaining 2.5 lb/d
60
55
Avg. lactating cow
50
45
Dry, pregnant cows
40
Veg.
Late Veg.
Boot/bud E. bloom Full bloom Hard seed
* Superior milking cow
Matching Animal Needs to Pasture Quality
Crude Protein
25
Cool season grasses
20
15
1000 lb cow* nursing calf or
10 500 lb steer gaining 2.5 lb/d
5
Dry, pregnant cows
0
Veg.
Late Veg. Boot/bud E. bloom Full bloom Hard seed
* Superior milking cow
DM basis
CP
Ca
9
0.03
6
1.5
P
0.32
0.11
Feed
Corn
Citrus pulp
DM
88
91
TDN
90
82
Wheat middlings
Cottonseed, fuzzy
Corn gluten feed
Distillers grains
90
92
90
90
80
92
80
90
18
23
23
27
0.17
0.16
0.36
0.11
1.0
0.7
0.82
0.43
Cottonseed meal
Soybean meal
92
90
75
84
49
49
0.2
0.8
1.1
0.2
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The time of day will effect affect the amount of
forage that the cattle will consume
Cattle have intensive grazing peaks at dawn and
dusk, with most grazing occurring in daylight
hours
Feeding supplements in the middle of the day
will be less disruptive on normal grazing activity
and will cause cattle to eat more forage than if
supplements are fed early in the morning


A supplemental feeding program to reduce
forage intake but maintain total energy intake
may be desirable
Rule of thumb: 1 pound of an energy-dense feed
reduces forage intake by 0.5 to 1 pound.
◦ The substitution rate





increases as supplement intake increases
increases as forage quality increases
decreases as the level of protein in the supplement increases
Greater for high starch feeds than highly digestible fiber
feeds
1% BW of high energy feed

Can be profitable but need to look at the
costs

Test your forage!!!!

Corn silage
◦ Typically need protein supplement

Hay
◦ Both energy and often protein
◦ Usually require high supplementation rates

Most forages deficient in one or more trace
mineral
◦ May need P and Ca

Supplementation of Trace Minerals may or
may not increase performance
◦ Cheap insurance

Ionophores improve feed efficiency and daily
gains in cattle
◦ 5 to 15% improvement in ADG
◦ 6 to 12% improvement in feed efficiency

Can be provided in a free-choice mineral or
molasses blocks
◦ Need to monitor intake

Mixing into a supplement can ensure adequate
intake
◦ 150 to 200 mg/hd/d in supplement
◦ ionophores can be hand fed every-other-day with
similar performance benefits as long as average daily
intake is the same

Suckling calves -low dose estrogen (but not potential
replacement heifers)

Stocker cattle-moderate dose estrogen or low dose
combination

Plane of nutrition is important for response
◦ Response is % of current ADG so higher ADG greater response (if nutrients
are there to support growth)
◦ If CP is marginal and using implant consider supplementing
◦ Effect of ionophores and implants are additive

Optimize profit

Think production per acre (with less input)

Manage both plant and animal
 Plant growth (yield and nutrient content)
 Animal nutrient intake

Forage quality varies greatly among and
within forage crops, and nutritional needs
vary among and within animal classes
◦ Try to match forage to animal needs

The more mature and fibrous (lower in
quality) a forage, the longer it takes to be
digested and the less an animal will consume.


The nutrient that is most limiting or deficient should
be supplied first
While protein and minerals can limit animal
performance, digestible energy is more likely to be
the limiting factor from forage in grazing situations.
◦ Exceptions stockpiled range and feeding straw


If extra protein or energy is needed be sure to
compare feeds per lb of nutrient needed when
selecting a feed
Provide mineral and ionophore to stocker cattle