The flock-mating of progestagen-synchronized ewes 2. The influence of time of ram introduction upon mating behaviour and lambing performance

Abstract

SUMMARYFour 2½-year-old Suffolk rams were each mated to groups of 24 Polled Dorset Horn ewes in which the oestrous cycles had been synchronized by the use of progestagen-impregnated vaginal sponges. Ram introduction occurred at either 24 or 48 hr after vaginal sponge withdrawal. Few ewes were in oestrus 24 hr after sponge withdrawal, but the majority were showing oestrus at the time of the 48-hr introduction. Mating behaviour and subsequent lambing performance of the ewes were recorded. All rams mated with the majority of their ewes. Rams introduced 48 hr after sponge withdrawal were found o t serve their ewes less frequently and over a more limited period, but they did succeed in mating with a greater proportion of their ewes during their first 30 services. There were no statistically significant differences in overall lambing rate between treatments, but the ratio of ewes lambing to ewes served on the 48-hr treatment was 92·5% compared with 72·2% for the 24-hr treatment (P < 0·05).