RELATIONSHIP OF PRODUCTION TO REPRODUCTIVE-PERFORMANCE IN ONTARIO DAIRY-COWS - HERD LEVEL AND INDIVIDUAL ANIMAL DESCRIPTIVE STATISTICS

Data were collected on reproductive, health and production events in 4 5 dairy herds distributed throughout southwestern and eastern Ontario. The data were collected between July 1990 and July 1993. The herds we re serviced by 11 different veterinary practices. Herd size ranged fro m 19 to 231 lactating cows, but 90% of the herds consisted of fewer th an 125 milking cows. Mean and median actual milk yields per cow per da y were 46.0 and 52.3 Ibs, respectively, with a minimum of 21.3 and max imum of 67.8 lbs. Mean and medium adjusted corrected milk yields were 56.0 and 62.3 Ibs, reflecting mean and median average days in milk of 199.0 and 198.5 d, respectively. Mean and median days in milk at the f irst estrus were 85.1 and 83.9 d, respectively, at first service 94.0 and 88.9 d, and at conception 126.3 and 115.5 d. Mean and median perce ntages of days open > 120 were 27.7 and 23.1%, respectively. The mean estrus detection rate was 48.3%, with a minimum of 28.4% and a maximum of 64.2%. The mean first service conception rate was 48.2%, with a mi nimum of 27.0% and maximum of 72.1%. The mean overall conception rate was 46.7%, with a minimum of 29.8% and a maximum of 70.7%. Mean and me dian lactation lengths were 341.1 and 338.5 d and the mean and median average dry days were 62.0 and 67.0, respectively. The mean lactationa l removal rate was 20.6%, with a range of 4.3 to 40.5%. Reasons for cu lling were available for 1381 cows. Low production accounted for 23.7% of the cullings; reproductive reasons, 20.6%; dairy sales, 13.4%; mam mary problems, 12.8%; and lameness, 9.9%. Lactational incidence rates for diseases were lower than previously reported for Ontario dairy her ds. The most commonly used therapeutic agents were GnRH (10.5%) and PG F (11.7%).