Ram-seeking activity associated with oestrous behaviour in ewes

Ram-seeking activity associated with oestrous behaviour was studied in entire and oestrogentreated spayed ewes. In spayed ewes, the incidence of both oestrous behaviour and ram-seeking activity increased with dose of oestrogen. All ewes could be induced to show ram-seeking activity, but only when injected with a dose of oestrogen greatly in excess of that needed to induce oestrous behaviour. The incidence of ram-seeking activity in entire ewes remained about 25 per cent lower than the incidence of oestrous behaviour at all stages of the breeding season. All ewes were capable of ramseeking activity, but normal levels of endogenous oestrogen probably were too low to induce a full response. In the absence of rams, spayed ewes injected with a dose of oestrogen sufficient to induce ram-seeking behaviour showed no increase in random walking activity. Ram-seeking behaviour appeared to depend not only on the internal stimulus of oestrogen, but also on the external stimulus provided by the presence of rams.