Abstract:
Animal Production in Australia INVESTIGATION OF A SHORT-ACTING PROSTAGLANDIN FOR INDUCTION OF CALVING N.E.JOHNSTON*, K.R. KING The use advantage of cloprostenol calving, and group of cows of short-acting drugs to a closer synchronization (Estrumate, I.C.I.), was the effects on the cows calving normally at the ** and D.P. HENNES SY* induce parturition in cows has the A synthetic prostaglandin, of calvings. administered to dairy cows to induce early and calves were examined and compared with a same time. A dose of 500 mcg Estrumate was given intra-muscularly to 22 cows an average A further 24 cows acted as of 18.3 days before their expected calving date. controls. All cows were observed every three hours to detect the time of calving. A blood sample was taken from each calf and a colostrum sample from each cow soon The immunoglobulin after calving (day 0), and then daily for three days. concentration of each serum and colostrum sample was determined using the Zinc Sulphate Turbidity test with standards of purified bovine gammaglobulin (Miles Laboratories) in foetal calf serum (Table 1). The induced cows calved an average of 14.6 days prematurely, with 16 (72%) The irnmunoglobulin calving 33 to 71 hours after injection with Estrumate. concentrations in the serum of induced calves were usually lower than those of the normal calves, but these differences were not significant due to the wide range of However at day 3, five of the induced values within each group (Table 1). The calves had values less than 15 mg/ml compared with one of 13 controls. colostral immunoglobulin concentrations did not differ between the normal and induced cows (Table 1). No measurements were made of total colostrum production, This may have been and thus total irrununoglobulins available to the calf. decreased in those cows which calved early since their milk production was significantly lower in the first week, but not thereafter. TABLE 1 Immunoglobulin concentrations (mg/ml) of calf serum and cow colostrum Twenty of the 22 cows treated with Estrumate had retained foetal membranes compared with none of 24 controls. The calving to first oestrus intervals were similar for both groups of cows, as were the calving to first ovulation intervals (as determined by an increase in serum progesterone levels). The induced cows took an extra 14 days from calving to conception, and only 16/22 became pregnant compared with 21/24 control cows. In this trial there was no real gain in using Estrumate to induce an early, synchronized calving. * Department of Agriculture, Attwood Veterinary Research Laboratory, Westmeadows, Vic. 3047. **Department of Agriculture, Animal & Irrigated Pastures Research Institute, Kyabram, Vic. 3620. 626