FSH or FSH plus LH superovulation in ewes following estrus synchronization with medoxyprogesterone acetate pessaries.

The estrous cycles of 28 ewes 9 to 10 months of age were synchronized with Medoxyprogesterone (MAP) pessaries. Superovulation was attempted by injecting either (follicle stimulating hormone) FSH or FSH plus Luteinizing Hormone (LH). MAP pessaries were in place for 12 days. FSH was administered (IM) to all ewes at 12-hr intervals over a 3-day period, 5 mg injected twice on day 11 after pessary insertion, followed by 4 and 3 mg twice daily on days 12 and 13, respectively. LH (25 mg injected IV) was given to 14 ewes within 8 hr after the onset of behavioral estrus. All ewes were hand mated with several rams at 12-hr intervals from the onset to the end of behavioral estrus. Ovulation, embryo recovery and fertilization rates were recorded for each ewe. Of 14 ewes injected with only FSH, 13 ovulated, with a mean ovulation rate of 8.2 +/- 5.6; embryo recovery rate averaged 62%, and fertilization rate was 97%. All 14 ewes given both FSH + LH ovulated, with an ovulation rate of 8.9 +/- 5.8 per ewe; embryo recovery averaged 70%, and 91% of all embryos recovered were fertilized. No statistical differences in ovulation, embryo recovery or fertilization rates were found between the FSH and FSH + LH superovulation treatment groups. In addition, no difference in the number of ewes showing estrus or duration of behavioral estrus was noted between FSH and FSH + LH treatments.

Synchronization of estrus in gilts with allyl trenbolone: fecundity after natural service and insemination with frozen semen.

The synthetic progestogen, allyl trenbolone, was fed daily to 60 gilts at 15 mg/gilt for 18 days. Sixty-eight gilts that came into estrus the same week as treated gilts served as controls. Gilts were checked for estrus twice daily and were artificially inseminated with frozen semen or bred by natural service. All but two treated gilts returned to estrus between 4 and 7 days after withdrawal of allyl trenbolone (mean = 5.6; SD = .82). The farrowing rate among gilts inseminated with frozen semen was significantly lower than that among gilts bred by natural service (52.5 vs 89.6%). The farrowing rate among synchronized gilts was similar to that among untreated gilts (70.7 vs 73.5%). Average total and live litter sizes at birth and litter size at weaning were significantly smaller for untreated gilts inseminated with frozen semen than for synchronized gilts inseminated with frozen semen or those of untreated gilts bred by natural service. Average litter size for synchronized gilts bred by natural service was not significantly larger than that for synchronized gilts inseminated with frozen semen or that of untreated gilts bred by natural service.

Conception rates in synchronized beef cows with and without monensin feeding.

Two groups of Hereford and two groups of Hereford crossbred beef cows were each divided into herds of 74 to 76 cows. Forty nine to 51 cows in each herd were synchronized with the Syncro-Mate-B (SMB) treatment and inseminated once between 48 and 52 hr after removal of the implant. The other 25 cows served as controls and were bred naturally. All herds received 2.27 kg/head/day of a corn-based supplement plus corn silage fed ad libitum for 15 days before and 20 days after the scheduled insemination date. In addition, one herd of each breed group was fed 250 mg of monensin/head/day during the same period. Overall conception rates for control and SMB-treated cows were 77 and 84.3%, respectively, and were not significantly different. Conception rates for the SMB-timed insemination were lower (P < .10) for Herefords than for crossbreds, averaging 34.9 and 48.5%, respectively. There was no difference in conception rates due to monensin treatment. Rumen samples taken 3 to 4 hr after feeding showed a lower ratio of acetate to propionate for Herefords fed monensin as a result of a lower proportion of acetate and a higher proportion of propionate in those animals.