Abstract

The live-weight response of light and heavy ewes to a range of pasture allowances was investigated in 3 experiments. Differential feeding levels prior to the commencement of Expt. 1 generated light and heavy ewes (52 v 57 kg live weight, P<0.001; 3.5 v 4.1 body condition score, P<0.01) that were subsequently offered pasture allowances of either 1, 2 or 4 kg DM/ewe/d for a 10-week period. Light ewes gained more weight than heavy ewes on all allowances. With time, ewes tended to approach a constant live weight in equilibrium with their level of feeding. Both light and heavy ewes harvested pasture to similar post- grazing residuals and rejected the dead material in the sward. In Expts, 2 and 3 low and high live weight ewes were selected from within large flocks of 4-tooth ewes that had been run as 1 mob (live weight 38 v 49 kg Expt. 2, 41 v 55 kg Expt. 3, P<0.001; body condition 1.8 v 2.4 Expt 2, 2.1 v 3.1 Expt, 3, P<0.01). Light and heavy groups were most grazed separately on allowances of 1.2 or 4 kg DM/ewe/d for 6 weeks although Expt. 3 partly comprised mixed groups for assessment of competition effects. No such effects were apparent on the higher allowance where light and heavy ewes had similar live-weight gains. On the lower allowance however, light ewes were more responsive than their heavier counterparts with this being less pronounced under mixed grazing. The implications for flock management are discussed.

BL, Smith, PP Embling, and MG Pearce

Proceedings of the New Zealand Society of Animal Production, Volume 43, , 217-220, 1983