Short-term under-nutrition affects feeding and sexual behaviour in oestrous-synchronized Saint Croix ewes (Ovis aries)

To determine the effect of short-term under-nutrition on feeding and sexual behaviour in oestrous sheep, the oestrus cycles of 51 Saint Croix ewes were synchronized, and they were randomly assigned to one of two groups. Each group was maintained on a Taiwan grass (Pennisetum purpureum) pasture for 102 h after sponge withdrawal. This diet provided 400 g of dry matter/100 kg of body weight/day, the total available for one group (T), whilst another group (T + C) received an additional 350 g/animal/day of concentrate. Before and after the experimental period, all animals received the additional concentrate. A pen with two one-way gates was located in the centre of each pasture to capture those ewes showing proceptive behaviour towards a ram tethered inside, while sexual receptivity tests were performed every 6 h for 102 h, starting at sponge withdrawal, by moving the ewes to an adjacent pen and exposing them to an intact ram. Foraging behaviour was recorded by scan samples before the sexual receptivity tests. Progesterone concentration was determined on days 2 and 11 after sponge withdrawal. Only 26% of the ewes in the T + C group and none in the T group displayed proceptive behaviour. In both groups, all ewes displayed sexual receptivity and ovulated. Grazing, rumination and walking were higher in T ewes. The frequency and the duration of lying were higher in the T + C than in the T ewes. It was concluded that the short-term nutritional deficiency induced changes in foraging behaviour and decreased ram-seeking behaviour in oestrous-synchronized ewes.