Initiation of Parturition in Dairy Cows with Dexamethasone. I. Cow Response and Performance1,2,3

Abstract

Parturition was initiated in 25 of 29 Holstein cows given dexamethasone (4.4mg/100kg body weight) intramuscularly at day 273 of gestation. Parturition occurred at 45.1±11.1h after injection. The 29 control cows which were compared to 29 induced cows had an average gestation length of 280 days. Calving difficulty was greater while birth weight of calves was 3.0kg less for the induced cows compared to control cows. Severity of udder edema did not differ between groups. Average daily milk production for the first 9 wk of lactation was 24.8kg and 27.8kg for the induced and control groups. Differences in milk fat or fat-corrected milk were nil. Changes in body weight were similar for all cows. Incidence of retained placental membranes was 76 and 10% for induced and control cows. Average days to first heat, days to first service, days to conception, and services per conception for induced cows were 58.4, 79.9, 117.8, and 2.0 and for control cows were 58.6, 82.3, 105.5, and 1.8. The incidence of milk fever in cows with no previous history was 24 and 10% for induced and control cows. Results of California Mastitis Tests taken at 15 and 30 days post calving were similar. Fat, protein, total solids, and gamma globulin content of the colostrum did not differ between groups.