Phenotypic and genotypic parameter estimations of some production traits of holstein friesian dairy cattle raised in a private enterprise in Diyarbakir province

This study was conducted to investigate the milk yield traits of Holstein Friesian cows raised on a private farm in Diyarbakır province and the effects of environmental factors on these traits. The research material consisted of 186 lactation records from 104 cows for the years 2022 and 2023. Key parameters such as lactation milk yield, 305-day milk yield, lactation length, and dry period were analyzed. The results indicated that the average lactation milk yield was 7,830±18.6 kg, 305-day milk yield was 6,517±12.4 kg, lactation length was 341±7.2 days, and dry period was 66±2.9 days. In 2022, the lactation milk yield (8,109 kg) was significantly higher than in 2023 (6,458 kg) (P<0.01). Similarly, the lactation length was longer in 2022, while 305-day milk yield and dry period were higher in 2023. The calving season did not have a statistically significant effect on any of the milk yield parameters. Although lactation order did not show a significant effect, the highest yields were observed in the fourth lactation. The persistence of lactation was evaluated using four methods, and it was found that a substantial portion of total milk yield was produced in the first 100 days, indicating a declining trend in milk yield over time. The heritability estimates for milk yield traits ranged from low to moderate: 0.12 for lactation milk yield, 0.14 for 305-day milk yield, and 0.02 for both lactation length and dry period. These findings suggest that environmental factors play a more prominent role than genetic ones in determining milk production traits, emphasizing the importance of herd management and nutrition strategies in improving productivity.