Dairy cattle breeding programs have been based in the selection for traits related to milk production. In this research a data set of 63 herds of East Azerbaijan province Holstein cattle, collected during 2002-2013 by the Iranian Animal Breeding Center was used to estim
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Dairy cattle breeding programs have been based in the selection for traits related to milk production. In this research a data set of 63 herds of East Azerbaijan province Holstein cattle, collected during 2002-2013 by the Iranian Animal Breeding Center was used to estimate the repeatability and heritability of three traits of economic importance. Genetic parameters for first three lactations of Holstein cows were estimated using repeatability models. Single-trait repeatability models were fitted for milk, fat and protein yields. The model contained milk frequency and herd-year-months of test-days (HTD) as fixed effects; effect of animals were the random effects. The estimated heritabilities in first three lactations for milk yield were 0.154, 0.263 and 0.334, for protein yield 0.134, 0.166 and 0.274 and for fat yield 0.059, 0.083 and 0.052. The estimated repeatability in first three lactations for milk yield were 0.475, 0.847 and 0.898, for protein yield 0.398, 0.479 and 0.678 and for fat yield 0.198, 0.281and 0.279. The results imply that milk traits for Holstein dairy cattle in east Azerbaijan, Iran are more heritable. Therefore, these traits can be employed by breeders as selection criteria in developing effective genetic improvement programs.
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