Influence of social interaction between rams on their serving capacity

The experiment was designed to test the hypothesis that social interaction between rams influenced their serving capacity and modified their preference for ewes.

The serving capacity and the preference for particular ewes was recorded on the first and seventh day of joining in 8 rams mated either individually or in pairs to 12 oestrous ewes. The serving capacity (mean number ejaculates/hour) was 50% lower in both dominant and submissive rams when working together compared with single-sire matings. However, when working together, 33% of the available ewes were served by the submissive ram and 12.5% were served by the dominant ram so that, in total, more ewes were served (total mean number ± SE of ewes served/ram when mated either individually or as a pair = 4.50 ± 0.89 and 5.50 ± 0.57, respectively). This resulted from a modification in ewe preference by the submissive ram.

In the absence of competition, the same ewes were observed to be preferred by most rams. This ewe “attractiveness” was found not to be a permanent characteristic, as the preferred ewes at one oestrus were not necessarily those most preferred at a subsequent oestrus.