Investigations Associated With the Transplantation of Bovine Ova

Summary. Synchronization of bovine oestrous cycles was studied with respect to methods of accomplishment. A total of 328 cows were recycled by: (a) daily subcutaneous injections of progesterone, (b) larger subcutaneous injections every 3rd day and (c) corpus luteum expression. Standing oestrous was exhibited by 262 cows. Twelve did not exhibit oestrus and fifty-four exhibited symptoms but refused mounting. Time between treatment and oestrus was 4·97 ±1 82, 6·52 ±1 ·25 and 2 ·84 ±0·68 days, respectively, for the three methods employed. Length of time between injection and oestrus did not differ significantly as influenced by day of initiation, the duration of injections or by superovulation. Differences between fifty-nine recycled and fifty-three control cows, with respect to rate of conception, were not significant nor were differences between the first and second services after recycling.