Impact of dystocia and cow/calf characteristics on mortality from 0 to 120 days of age in Japanese Black calves in commercial cow-calf operations

Calf mortality severely affects productivity in the beef industry. The present study was conducted to assess the calf mortality risk (CMR) in Japanese Black calves and investigate potential associations between calf/cow information and the CMR. Records for calves born between April 2006 and March 2010 were extracted from an existing database, which included production data on commercial cow-calf operations in Miyazaki, Japan. The study group comprised 40,462 calves born to 15,600 cows on 908 farms. Because calves on the studied farms were weaned at approximately 4 months of age, the calf records were collected from birth to 120 days. The CMR was calculated as the number of dead calves divided by the number of surviving calves. Mixed-effect multivariable logistic regression modeling was used to determine potential associations between the CMR and the factors hypothesized to influence that risk. CMR analyses were performed separately for the following production stages: days 0-30, days 31-60, days 61-90 and days 91-120 after birth. Of the 40,462 calves, 1465 died during days 0-120 after birth, and the CMR was 3.6 %. Of the 1465 dead calves, 35.9 % died within 10 days after birth. During the 0-30-day period, the CMR was associated with dam parity, calving status, gestation length, sex, birth season and twin births (P 0.05), but not with the number of inseminations to conception. Low parity, dystocia, gestation lengths 280 days and 301 days, male calves, calves born in autumn and winter and twin births yielded higher CMRs. Low dam parity also yielded higher CMRs during the 31-60-day, 61-90-day and 91-120-day periods (P 0.05), but no other factors were associated with the CMR during these periods. Thus, various cow and calf factors were shown to be associated with CMRs in Japanese Black calves, and calves with these factors should be considered high-risk calves.