Factors influencing voluntary forage intake in ewes during the last two months of gestation are not sufficiently documented. The effects of hay quality and level of concentrate were studied by Orr and Treacher (1984) but other factors such as prolificacy or level of body reserves are poorly understood (Theriez et al., 1987). Furthermore most of the results come from animals kept in individual pens abolishing the effect of behavioural interactions. The purpose of the present experiment was to examine the effect of the number of gestated lambs and level of concentrate on voluntary intake of hay by ewes kept in a group.

A flock of 120 multiparous Manchega dairy ewes were synchronised using intravaginal progestagen and injected with 400 IU of PMSG (Chronogest, Intervet). After ultrasonic pregnancy diagnosis at 60 d after mating (Toshiba Sonolayer, Mod.Sad-32B, 5.0 MHz), two groups of 30 twin or single pregnant ewes were selected and distributed in a factorial design 2x2x3. Factors were number of foetus (S = l, T=2) and level of concentrate (H=600 g/d, L=300 g/d) with 3 replicates of 5 ewes each.