The effect of body condition and previous nutrition on the herbage intakes of ewes grazing autumn pastures at two sward heights

Abstract

To examine the effects of body condition and previous nutrition on the herbage intake of ewes grazing swards of different heights in autumn, 96 Scottish Blackface X Border Leicester ewes with a wide range of body condition (score 1·75 to 3·50), were initially housed and given 50 g dry matter (DM) per kg metabolic live weight (M)^0·75 per day (treatment L) or 95 g DM per kg M^0·75 per day (treatment H) of a pelleted dried grass diet (11·6 MJ metabolizable energy per kg DM) for 6 weeks after weaning in July. The H ewes gained more live weight (9·0 v. 2·7 kg) and body condition score (0·39 v. 0·17) than the L ewes. Half the animals from each treatment were then allocated to each of two ryegrass pastures with a sward height of 5 cm (LS) or 10 cm (HS) for a further 6-week grazing period. During the grazing period there was no significant effect of indoor feeding level on herbage intake, but the L ewes gained more live weight (6·4 v. 5·0 kg) than the H ewes. On the HS, compared with the LS sward, mean herbage intakes were higher (70·0 v. 60·5 g DM per kg M^0·75) as were gains in live weight and condition score (7·9 v. 3·4 kg; 0·18 v. 0·0). There were no interactions between the effects of sward height and previous feeding level on herbage intake. Ewes in low body condition (< 2·5) at the start of the grazing period ingested the same amount of herbage on both swards (70·3 g DM per kg M^0·75) whereas ewes in high body condition (> 2·5) ingested more (67·0 v. 51·6 g DM per kg M^0·75) on the HS compared with the LS sward. The responses of ewes in low and high body condition to different sward heights are discussed in relation to appetite drive and aspects of grazing behaviour.