EVALUATION OF INTRAUTERINE INSEMINATION OF SHEEP WITH FROZEN-SEMEN - EFFECTS OF TIME OF INSEMINATION AND SEMEN DOSE ON CONCEPTION RATES

The field application of a laparoscopic technique to permit intra-uterine insemination of ewes with frozen-thawed semen was examined in two trials, conducted over successive years, to (i) determine the optimum time of insemination relative to sponge removal/pregnant mare's serum gonadotropin (PMSG) injection and (ii) establish the relationship between semen dose and conception rate. Pooled semen was used in both trials, and each involved > 900 ewes in a number of commerical flocks. Maximum conception rates were achieved when insemination was conducted between 54 h and 60 h after sponge removal/PMSG injection. However, there was no significant difference in conception rate when motile sperm numbers were reduced from 52.2 X 10(6) to 13.0 X 10(6) motile sperm per uterine horn. The overall conception rates (pooled over flocks and treatment groups) were 56% and 58% for the two trials, with a wide degree of variation between flocks in both cases (45% to 79% for trial 1 and 45% to 69% for trial 2). However, there was evidence for consistent differences in conception rates between the six flocks involved in both years of the trials.