Effects of melatonin, progestagens, and the ram on out-of-season reproduction in Swedish landrace finewool sheep

One hundred twenty-one Swedish Landrace Finewool ewes were treated with pro gestagen sponges (P), teaser ram stimulation (R), or melatonin implants plu s teaser ram stimulation (M) in preparation for breeding with whole rams in August. Blood progesterone analyses from ewes in the R and M groups gave n o evidence of luteal activity before the introduction of teaser rams. There were no significant differences between treatments for pregnancy rate (sim ilar to 90%). The P group had the most compact lambing season, while median breeding dates for M and R groups were delayed by one cycle. In those grou ps, the introduction of breeding rams was later found to have been too late . M and R differed significantly for probable conception date but not for l ambing dates. Circa 30% of M ewes did not have a short 6 day ovulation cycl e after the first ovulation, which resulted in a less concentrated lambing season than the other methods. Although no significant differences in litte r size were seen among the 3 treatments, M had the highest group average, 2 .25. The ewes in this study were not in very deep anestrous in the middle o f August. This supports the conclusion that treatment with exogenous hormon es is not necessary to breed Swedish Landrace Finewool ewes successfully in late August/early September.