The influence of rams on onset of oestrus in Merino ewes in the spring

Abstract

Association with rams had a stimulating influence on the onset of oestrus after anoestrus in the spring. Smell and sound of the rams was sufficient to provide the stimulating influence. Direct contact with rams certainly was not necessary. Ewes which had been held well separated from rams from the beginning of July were permitted varying degrees of association with rams for 11–12 hr daily for 2 weeks in November. Some could smell, hear, see, and have actual contact with the rams; others could smell, hear, and see them only; others could smell and hear them only. These ewes, along with others which had remained well separated from rams during the same period, were then run together with raddled vasectomized rams continuously. Almost all ewes experienced oestrus during the following 26 days. However, most ewes which had previously had some association with rams experienced it first within 17 days whereas most of those which had been previously kept separate from rams did so between the 18th and the 26th day. The results in all groups which were associated with rams were closely similar irrespective of the nature of the association.