This study was conducted to compare of random regression (RR) animal and sire
models for estimation of the genetic parameters for production traits of
Iranian Holstein dairy cows. For this purpose, the test day records were used
belonged to first three lactations of cows and for, milk, fat and protein
yields traits where, collected from 2003 to 2010, by the national breeding
center of Iran. The genetic parameters were estimated using restricted
maximum likelihood algorithm. To compare the model, different criterion
-2logL value, AIC, BIC and RV were used for considered traits. Residual
variances were considered homogeneous over the lactation period. Obtained
results showed that additive genetic variance was highest in the beginning
and end lactation and permanent environmental variance was highest in
beginning of lactation than other lactation period. Heritabilities estimate
for milk, fat and protein yields by RR animal and sire models were found to
be lowest during early lactation (0.05, 0.04 and 0.07; 0.05, 0.19 and 0.13;
0.14, 0.19 and 0.15, for milk, fat and protein yields and in first, second
and third lactation respectively). However, estimated heritabilities during
lactation did not vary among different order Legendre polynomials, and also
between RR animal and sire models. The variation in genetic correlations
estimate in the RR animal and sire models was larger in the first lactation
than in the second and third lactations. Thus, based on the results obtained,
it can be inferred that the RR animal model is better for modeling yield
traits in Iranian Holsteins.
Genetic parameters for production traits in New Zealand dual-purpose sheep, with an emphasis on dagginess1
