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چکیده
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Production traits are the most important traits which effect economic efficiency of the diary cattle. Estimation of genetic trends is necessary to monitor and evaluate the success of breeding programs. In this study production traits data of the Iranian dairy herds were obtained from the National Animal Breeding Center of Iran. The dataset included first lactation records of milk, fat and protein yields. Records were adjusted for milking times (2X) and 305 days in milk. Data were analyzed by Matvec program and also a using a multiple trait mixed linear model was fitted to obtained BLUP of the breeding value of the animal. Genetic trend was estimated as the linear regression of average estimated breeding values on the birth year. The 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. Genetic trends for all traits was positive and significant (P<0.01). Average environmental trends values for milk, fat and protein yields were 88.44, 3.78 and 2.06 kg/year, respectively. The absolute value environmental trends were greater for all traits. The result of this study show that genetic improvement for production traits was acceptable level in the Holstein herds of Iran.
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