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چکیده
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Estimation of genetic trends is necessary to monitor and evaluate selection programs. Production traits are the most important traits which effect economic efficiency of the diary cattle. Data of Holstein cattle were obtained from the National Animal Breeding Center of Iran. Data included first lactation records of milk, fat and protein yields. Data were analyzed using a multitrait animal model and Matvec program. Genetic trend was estimated as the linear regression of average estimated breeding values of animals on the birth year. Estimated genetic trend values for milk, fat and protein yields were 33.84±2.81, 0.64±0.05 and 1.00±0.08 kg/year, respectively. The genetic trends for all traits were positive and significant (P<0.01). The result of this study supports the existence of a acceptable genetic gain for the production traits. However, more emphasis is devoted to milk volume compared to the component traits.
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