Effects of Lactation Stage and Milk Yield on Reproductive Performance in Holstein Dairy Cows

【This study aimed to improve the reproductive efficiency of dairy herds by comparison and analyzing estrous appearance rate, conception and non-conception rate according to the stage of lactation using the lactation and reproductive records of average (less than 10,000 liters milk in 305 days) and high yielding (more than 10,000 liters milk in 305 days) Holstein cows (n=102). Milk production and reproduction data were collected between January 2010 and December 2012 from Holstein cows kept in the commercial dairy farms. Average (n=32) and high yielding (n=24) Holstein cows used to analyze the relationship between milk yield and reproductive performance. Our results showed that estrous appearance rate according to the stage of lactation was 25.0% (30~59d), 40.6% (60~89d), 25% (90~110d) and 9.4% (>111d) in average yielding cows and 16.7% (30~59d), 20.8% (60~89d), 12.5% (90~110d) and 50.0% (>111d) in high yielding cows, respectively. Conception rate according to the stage of lactation was 87.5% (30~59d), 61.5% (60~89d), 75.0% (90~110d) and 66.7% (>111d) in average yielding cows and 25.0% (30~59d), 0% (60~89d), 33.3% (90~110d) and 50.0% (>111d) in high yielding cows, respectively. Days between parturition and conception was 23.7% ( 210 d) in average yielding cows and 69.0% ( 210d) in high yielding cows, respectively. Conception rate from 110 days postpartum in high yielding cows was 41.7% (110~150d), 50.0% (151~180d) and 50.0% (>181d). Body condition score (BCS) in 120 days postpartum was $2.64{\pm}0.1$ in average yielding cows and $2.28{\pm}0.1$ in high yielding cows, respectively.】