Bovine egg transplantation. Superovulation, non-surgical recoveries and transfers.

Lactating dairy cows were superovulated with a pregnant mare serum gonadotrophin (PMSG)/cloprostenol (PG) regimen in their mid-luteal phase (day 10). The average interval from the PMSG injection to heat was 4.1 +/- 0.05 days. First insemination occurred 18--24 hrs after standing heat and the second insemination 12--18 hrs later. Six to eight days later (the day of recovery) the superovulatory response was assessed. The variation in number of ovulation points (corpora lutea, C.L.) was sizable, and right ovary (4.1 C.L./donor) appeared more active than left ovary (3.3 C.L./donor). The non-surgical embryo collection equipment was developed for practical use on the farms and it was possible to recover 6.0 +/- 0.6 eggs per donor (54 +/- 5% recovery rate). Approximately half of these (54.2%) were considered viable, and suitable for either direct transfer or freezing, Other eggs were retarded (5.8%), degenerated (25.7%) or unfertilized (16.3%). Several influential factors were examined and there was only little conclusive evidence for any specific effect on the superovulatory response and/or egg number and quality. The non-surgical transfer experiments with a common insemination gun was encouraging and gave rise to a pregnancy rate of 56%.