Factors affecting the reproductive performance of fat-tailed ewes inseminated with laparoscopy in the late breeding season

The reproductive responses to one and two inseminations of frozen-thawed semen were compared in fat-tailed ewes which had previously been used in controlled reproduction programs aimed at estrus synchronization, multiple ovulation embryo transfer, and out of breeding season. In the trials, mature dry (n = 50) ewes in progestagen-induced estrus were inseminated 54 to 56 h after sponge removal. Half of the ewes received a second insemination 6 or 8 h later. The quality of the semen was determined by evaluating sperm motility after thawing. Association between factors included in this study and sex ratio was also investigated. The previous breeding programs effected ewe’s subsequent fertility and the range in lambing rates observed was from around 33% to over 75%. Higher (P < 0.05) lambing rate (56% versus 29%) and litter size (1.8 versus 1.2) indicated an advantage of two inseminations. Post-thaw evaluation of frozen semen was good indicator to achieve acceptable pregnancy rate. Sex ratio was significantly affected by the previous breeding program, one or two inseminations, and postthaw quality of frozen semen.