SELECTION INDICES FOR THE HUNGARIAN SHEEP
POPULATION
Komlósi, I.
Nagy, I.
Sáfár, László
Hajduk, Péter
Debrecen University
of Agricultural Sciences
Debrecen, Hungary
Hungarian Sheep Breeders Association
Budapest, Hungary
ABSTRACT
The aim of the study was to calculate selection indices for the main sheep breeds that are simple and easy to
use by the farmers. The main breed types were the Merino, the terminal and milk breeds. The aggregate breeding
value for the indices comprised number of lambs born (NLB), weaning weight (WW), yearling weight (YW) and
greasy fleece weight (GFW) for the Merino; NLB, WW and YW for the terminal; and NLB, WW and milk
production (MP) for the milk breeds. Deriving economic values, the present pricing system was used. Index
measurements were NLB from the dam, MP of the dam, own WW, own YW, own GFW, progeny WW and
progeny MP. NLB, WW and MP were adjusted for environmental factors. Literature and unpublished estimates
of phenotypic and genetic parameters were used. Indices were calculated for lamb, yearling, dam and ram age
groups. The standard deviation of the index varied between 18 and 25, the correlation between the index and the
aggregate genotype varied between 0.55 and 0.62. The index was scaled to have an average of 100.
INTRODUCTION
The present selection scheme for the pedigree flock includes independent culling levels in
the selection of the replacements at the age of two years with indices computed for lambs,
yearlings, ewes and rams. In the calculation of these indices the individual record is compared
to the flock and national standard of the breed. The indices are not genetic indices as proposed
by Hazel (1943). Because of the time needed for calculating the index centrally, the farmers
often get the selection list late. The aim of this study was to derive genetic selection indices
that can be easily applied on farms, and breeding values are presented at the time when the
input records are available.
MATERIAL AND METHODS
The Hungarian sheep recording scheme has stored data in a computerized central database
since 1987. These data were used in the study. The breeding goals in the selection were
number of lambs born (NLB), weaning weight (WW), yearling weight (YW) and greasy
fleece weight (GFW) for the Merino; NLB, WW and YW for the terminal; and NLB, WW
and milk production (MP) for the milk breeds. NLB was used instead of number of lambs
weaned, since no record is kept whether the lamb was reared by the mother. Deriving
economic values, the present pricing system was used (Table 1.). Since a higher prolificacy is
desired for all breeds, the present price was doubled for twin lambs. The relative economic
weights were close to earlier unpublished results of the authors, being 53:3:1 for
NLB:WW:GFW, respectively.
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Table 1. Breeding objectives and economic weights
Trait
s.d
economic weight
Number of lambs born
0.47
Weaning weight (kg)
3.0
600 HUF
Yearling weight (kg)
4.5
180 HUF
Greasy fleece weight (kg)
0.53
180 HUF
Milk (l)
9 600 HUF
30
150 HUF
Environmental effects that significantly influenced the measured traits were analysed by
the LSMLMW programme of Harvey (1960), and multiplicative factors were computed.
In the case of the first lambing the NLB was multiplied by 1.1. After the first lambing the
averages of NLB were used. The weaning weight was also corrected according to the lambing
(Table 2.)
Table 2. Correction for the measured traits
Trait
Class
Sub-class
Weaning weight
Litter size
Single
Twins
Triplets
1.0
1.15
1.3
Parity
1
2
3,4,5
6<
1.07
1.02
1
1.05
Parity
1
2
3,4
5
6<
1.2
1.1
1
1.1
1.2
Milk production
Multiplication factor
The age of lamb at weaning was also adjusted with the following equation:
lamb’s WW –0.2 * (age of lamb – average age of the lambs weaned).
Phenotypic and genetic parameters first were calculated by the LSMLMW, then these
estimates were used as input data for the MTDFREML programme (Boldman et al., 1993). If
estimates of genetic correlations between pairs of traits were of doubtful validity they were
assumed to be equal to the phenotypic correlation, or were replaced by information available
from the literature (Mavrogenis and Constantinou, 1991; Finci, 1957;Turner, 1972; Croston et
al, 1980) (Table 3.).
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Table 3. Parameters used in the study for calculation of the selection index
NLB
WW
YW
GFW
MP
NLB
0.15+
0.1
0.1
0.0
0.1
WW
0.2
0.3
0.6
0.2
0.0
YW
0.2
0.6
0.5
0.3
0.0
GFW
0.0
0.2
0.2
0.4
*
MP
0.1
0.0
0.1
*
0.2
+ Heritability values on the diagonal, phenotypic correlations above and genetic correlations below the diagonal
RESULTS
The assumptions made for the construction of the index were that there was no inbreeding,
there were no genotype by environment interaction, there were no important maternal effects
and that mating was not assortative. Each index was standardized to a mean of 100 and
standard deviation of 20.
The selection objective remains constant, but different information was used on relatives,
and different selection intensity was applied at each stage. In this study each stage is treated
as an entirely separate operation. The replacement rate is 20-25% on the female and 4-6% on
the male side.
Lamb index
Information used for calculating the lamb index were average dam’s NLB , own weaning
weight. For the milk breeds the dam’s milk production was added (Table 4.).
NLB, WW and MP were adjusted for environmental factors.
Table 4. The b values in the lamb index
Hungarian Merino
Terminal breeds
Milk breeds
Dam’s NLB
16
16
13
Lamb’s WW
5
5
4
Dam’s MP
-
-
0.3
Yearling index
Information used for calculating the yearling index were average dam’s NLB, own
weaning weight, yearling body weight and greasy fleece weight. For the milk breeds the
dam’s milk production was added (Table 5.).
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Table 5. The b values in the yearling index
Hungarian Merino
Dam’s NLB
10
Terminal breeds
Milk breeds
10
8
Yearling’s WW
2.5
2.5
2
Yearling’s W
1.2
1.2
1
-
-
0.2
0.6
-
-
Dam’s MP
Yearling’s GFW
Ewe index
Information used for calculating the ewe index were average own NLB, WW of the
progeny. For the milk breeds the dam’s milk production was added (Table 6.).
Table 6. The b values in the ewe index
Hungarian Merino
Terminal breeds
Milk breeds
15
15
10
WW of lambs
4
4
3
MP in the first lactation
-
-
0.3
NLB at lambings
Ram index
Ancestry, own and progeny information was used in the ram index. For the milk breeds,
the index includes the prolificacy and the milk production of the daughters (Table 7.).
Table 7. The b values in the ram index
Hungarian Merino
Dam’s NLB
7
Terminal breeds
Milk breeds
8
-
Dam’s MP
-
-
0.1
YW
1
1.5
0.5
GFW
0.5
-
-
WW of the prog
2
2
1
NLB of the daugh.
-
-
5
MP of the daugh.
-
-
0.2
The standard deviation of the indices varied between 17.62 and 25.29. The correlation
between the index and the aggregate genotype varied from 0.54 to 0.62. The regression of
traits on index were 0.0031 for NLB, 0.021-0.045 for WW, 0.05-0.11 for YW, 0.0027 for
GFW, and 0.17 for MP in the case of the ram indices.
199
CONCLUSIONS
The production progress in recorded flocks has not been considerable during the last 10
years, partly because of the selection policy. The largest improvement for litter size is the
most demanding. Index values of the present and that of the lamb and ewe indices calculated
from this study were compared. No differences were obtained for single lambs in ranking,
which had average weaning age. Large differences were found for twins and triplets, which
had weaning age different from the average. So the main difference of the present and the
indices calculated in this study is the adjustment. On-farm calculation of indices is greatly
desired by the breeders. The use of breeding values estimated by BLUP is being investigated.
REFERENCES
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use of MTDFREML. In: USDA.
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Finci, M. 1957. The improvement of the Awassi breed of sheep in Israel. In: Bull. Res. Coun.
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in Chios sheep. In: Technical Bulletin 131. ARI-MANS. Nicosia.
Turner, H.N. 1972. Genetic interactions between wool, meat and milk production in sheep.
In: Animal Breeding Abstracts. 40.4. 621-634. p.
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