Akademik Veri Yönetim Sistemi
LARGE ANIMAL REVIEW, cilt.31, sa.6, ss.309-315, 2025 (SCI-Expanded, Scopus)
The primary goal of breeding organisations focused on sustainable and profitable milk production is to improve milk yield traits in dairy cattle. For this reason, the dairy industry has prioritised improving the genetics of dairy cattle to increase milk yield. The objective of this study was to estimate variance components and genetic parameters for 305-day milk yield (305-dMY), and to determine the effects of environment (calving season)-and animal-based factors (breed and parity) on 305-dMY in Simmental, Holstein, and Brown Swiss cows. The data set consisted of 19,454 records of 305-dMY obtained from 10,282 lactating Simmental, Holstein and Brown Swiss cows and 1,045 sires collected by the Cattle Breeders Association, between 2004 and 2018 in Kastamonu, Turkiye. A mixed ANOVA model was used to determine the effect of breed, parity, calving season and farms on the 305-dMY of cows. The model included three fixed effects: breed, parity and calving season and a random effect: farms. Variance components and breeding values were estimated in a Bayesian JWAS framework, using the conventional model within a Bayesian setting. Genetic parameter estimates were derived from the posterior distributions of the effects, obtained from an Markov Chain Monte Carlo run of 50,000 iterations with a first 5,000-iteration burn-in. The results indicated that 305-dMY was significantly affected by breed, parity, and calving season (P<0.001). The highest 305-dMY in Holstein cows was determined to be 5264.16 +/- 25.77 kg. The 305-dMY of cows calving in winter was higher than in other seasons (spring, summer and autumn). The mean inbreeding coefficient was found to be 0.091. The estimates of heritability for Simmental, Holstein, and Brown Swiss were 0.061, 0.208 and 0.129, respectively. The genetic trend for estimates of breeding values (EBVs) of 305-dMY was found to be 5.62 kg/year. The repeatability estimates for Simmental, Holstein and Brown Swiss were observed as 0.100, 0.277 and 0.199, respectively. The results indicate that the moderate heritability and repeatability estimate for 305-dMY, suggest that genetic gain can be obtained for these traits through genetic selection of Holstein cows. However, improving the performance traits of Simmental and Brown Swiss cows could be obtained through improving management conditions.