Effect of level of food intake on the reproductive performance of ewes in different levels of body condition at mating, following passive immunisation against testosterone

Extract

In a 2 x 2 x 2 experiment, 296 Scottish Blackface ewes were fed to achieve one of 2 levels of body condition (high : C.S. ⩾ 2.75; low : C.S. ⩽ 2.50). Half of the ewes of each condition group were then fed dried grass pellets ad libitum with 300 g hay/ head/day (high intake); the remainder were fed a liveweight maintenance ration of 750 g pellets and 400 g hay/head/day (low intake) between 14 days before and 8 days after joining. Thereafter, feed levels for both groups were gradually adjusted to 1250 g pellets and 400 g hay/head/day which was fed until mid pregnancy after which they were fed according to foetal load. Mean daily inatkes of dried grass pellets for ewes fed ad libitum were 2.45 and 2.27 kg fresh weight/head/day for ewes in the low and high condition groups respectively. The patterns of liveweight and condition score changes associated with these feeding regimes are summarised in Table 1.