ORIGINAL PAPER
Genetic parameters for somatic cell score for Polish
Black-and-White cattle estimated with a random
regression model
1 1 | Department of Genetics and Animal Breeding, Cracov Agricultural University,
Al. Mickiewicza 24/28, 30-059 Kraków, Poland |
2 | Department of Animal Breeding and Production, Cattle Breeding Division,
Warsaw Agricultural University,
Nowoursynowska 166, 02-787 Warszawa, Poland |
CORRESPONDING AUTHOR
E. Ptak
Department of Genetics and Animal Breeding, Cracov Agricultural University, Al. Mickiewicza 24/28, 30-059 Kraków, Poland
Department of Genetics and Animal Breeding, Cracov Agricultural University, Al. Mickiewicza 24/28, 30-059 Kraków, Poland
Publication date: 2007-09-06
J. Anim. Feed Sci. 2007;16(3):357–369
KEYWORDS
ABSTRACT
Genetic parameters for somatic cell score (SCS) for Polish Black-and-White cattle were
estimated using 52,599 test day records from the first six lactations of 8,418 cows, and the Bayesian
method via Gibbs sampling. The two-trait random regression (RR) model included fixed herd-year-month of test effect, fixed regressions within genetic group by age at calving by season of calving
subclasses, and random regressions for additive genetic and permanent environment effects. First
and subsequent lactations were treated as separate traits. Fourth-order Legendre polynomials were
used for regressions. There were 200,000 samples of (co)variances for random effects generated
with the first 20,000 samples as the burn-in period.
Genetic variances were in the range of 0.37 to 0.76 throughout first parity and 0.43 to 0.91
throughout later parities, with averages of 0.41 and 0.48, respectively. Variances for permanent
environment increased from 1.04 to 1.37 throughout the first, and from 1.11 to 2.00 throughout
subsequent parities. Estimates of heritabilities were from 0.11 to 0.20 for first and 0.13 to 0.22 for
subsequent lactations, indicating stronger genetic resistance to mastitis in later parities. The highest
values of heritability were observed at peripheries. Genetic correlations for SCS between first and
later parities for different days in milk (DIM) were all less than 0.5, with the highest values in
midlactation.
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