THE EFFECT OF BODY CONDITION AND PREVIOUS NUTRITION ON THE HERBAGE INTAKES OF EWES GRAZING AUTUMN PASTURES AT 2 SWARD HEIGHTS

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 bo dy 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 (treatm ent L) or 95 g DM per kg M0.75 per day (treatment H) of a pelleted dri ed grass diet (11.6 MJ metabolizable energy per kg DM) for 6 weeks aft er 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 ani mals from each treatment were then allocated to each of two ryegrass p astures 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 significa nt effect of indoor feeding level on herbage intake, but the L ewes ga ined more live weight (6.4 v. 5.0 kg) than the H ewes. On the HS, comp ared with the LS sward, mean herbage intakes were higher (70.0 v. 60.5 g DM per kg M0.75) 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 ef fects of sward height and previous feeding level on herbage intake. Ew es in low body condition (< 2.5) at the start of the grazing period in gested the same amount Of herbage on both swards (70.3 g DM per kg M0. 75) whereas ewes in high body condition (> 2.5) ingested more (67.0 v. 51.6 g DM per kg M0.75) on the HS compared with the LS sward. The res ponses of ewes in low and high body condition to different sward heigh ts are discussed in relation to appetite drive and aspects of grazing behaviour.