Estimation of variance components and genetic parameters for milk yield traits of jersey cattle raised in Gökhöyük agricultural enterprise

This study was conducted using 1378 lactation records from 587 Jersey cows that calved between 2017 and 2021 at the Gökhöyük Agricultural Enterprise located in Amasya, Turkey. The research aimed to evaluate milk yield traits (lactation milk yield, 305-day milk yield, milking duration, and dry period length) and a reproductive trait (calving interval), and to analyze the effects of environmental factors such as calving year, season, age, and lactation number on these traits. The average lactation milk yield was 7351.0±84.7 kg, the 305-day milk yield was 5952.9±40.1 kg, milking duration was 323.3±3.3 days, and the average dry period length was 60.2±0.3 days. The mean calving interval was calculated as 395.6±2.0 days. Calving year and age had statistically significant effects on both lactation milk yield and 305-day milk yield. A strong positive phenotypic correlation (r=0.829) was observed between lactation milk yield and 305-day milk yield, while a moderate positive correlation (r=0.532) was found with milking duration. Heritability estimates were 0.12 for lactation milk yield and 0.14 for 305-day milk yield, indicating low to moderate genetic influence on these traits. Based on the findings, Jersey cattle were found to possess high milk production potential. However, environmental factors significantly influenced performance, and sustainable productivity should be supported through appropriate management, care, and breeding strategies.