2022 Volume 10 Issue 1 Pages 55-61
Here, we investigated the effects of service sire breed (Holstein and Japanese Black) on conception rate at first service for Holstein females in Hokkaido, Japan. Fertility records of Holstein cows and heifers that calved between 2010 and 2019 were collected through the Dairy Herd Improvement Program by the Hokkaido Dairy Milk Recording and Testing Association. Data included 2,019,493 records with a flag 1 for conception success and 0 for failure. We used a three-trait (conception in heifers, in first lactation, and in second lactation) animal model containing herd-year at service, month at service, and age as fixed effects, and service sire-year at service, animal, and residuals as random effects. Conception rates at first service ranged from 55% to 59% for heifers, 39% to 41% for first lactation, and 37% to 38% for second lactation. For BLUP of sire effects in each calving, the mean effects of Japanese Black bulls were 0.01 to 0.03 higher than those of Holstein bulls.
