The effect of breed, season and competition on mating behaviour of rams

Abstract

Rams of three breeds were mated at monthly intervals for one year in small paddocks to a group of 36 ovariectomized ewes that received a series of standard progesterone and oestrogen injections. Border Leicester rams were less active than Merino and Dorset Horn rams in the summer but not in spring and autumn. In a second series of tests, rams were mated singly or in groups of three to groups of 10 or 20 oestrous ewes some of which were tethered. Rams mated singly, mounted most ewes in groups of 10, tethered or free, but failed to mate with many more of the ewes when the group size was increased to 20. The same rams, working in competition with other rams, mounted significantly more ewes from these larger groups.