Authors: ADNAN ÜNALAN, ZEYNEL CEBECİ
Abstract: In this study, 3484 milk yield records (1520 first, 1206 second and 758 third lactations) obtained from 1816 cows born between 1990 and 1997 in the Holstein-Friesian herd of Ceylanpınar State Farm were used to estimate the heritabilities, and genetic and phenotypic correlations between lactation milk yields using an individual animal model and the restricted maximum likelihood (REML) method. In the model studied, 305-day milk yields were used and individual animal effects were assumed to be a random effect, calving year and calving months were fixed effects, and calving age (as months) was a covariate, and all of these factors affected milk yields in a statistically significant manner (P < 0.01). Means of 305-day milk yields for the first, second and third lactations were 5046.3 ± 31.13 kg, 5175.8 ± 37.02 kg and 5268.2 ± 47.32 kg, respectively. Heritabilities for the first, second and third lactations’ milk yields were 0.297 ± 0.025, 0.369 ± 0.027 and 0.359 ± 0.034, respectively. Genetic correlations between the first and second, first and third, and second and third lactations were positive and statistically significant (0.738 ± 0.017, 0.632 ± 0.022 and 0.742 ± 0.024, respectively). Furthermore, for the same pairs of lactation numbers indicated above, phenotypic correlations were also positive and statistically significant (0.569 ± 0.021, 0.487 ± 0.052 and 0.542 ± 0.031, respectively).
Keywords: Heritability, genetic and phenotypic correlation, milk yield, Holstein Friesian, REML
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