Fertilization and return rates in Bungaree and Peppin Merino ewes mated in autumn

Abstract

A series of studies was conducted in 1968 and 1969 to compare fertilization rates, return rate, and sperm distribution in the genital tract in Bungaree and Peppin Merino ewes. Differences in lambing rates of the two ewe strains were demonstrated, but there was no major difference in fertilization rate in either year. A significantly higher proportion of Bungaree ewes had less than 1000 sperm in the fallopian tubes 24 hours after service, but there were no significant differences in any other character examined. Contrary to an earlier report, fertilization failure is unlikely to have been a major cause of a difference in the fertility of the two strains in the two years, and embryonic loss is likely to have made a significant contribution to the difference in their fertility.