Spring and summer pasture feeding and ewe reproduction and wool growth

Abstract

Effects of pasture feeding level during lactation and over summer on ewe wool growth and ovulation rate were assessed in 1983-84 and 1984-85. Two levels of pasture feeding (lactation high and lactation low) from parturition to weaning (10 weeks) produced 8 to 10 kg liveweight difference in ewe liveweight at weaning. Groups (n = 40) were offered pasture allowances of 0.8, 1, 1.4, 2 or 5 kg DM/ewe/day from weaning until after the third synchronzied oestrus in April. Ewes on the lower allowances tended to reach a stable liveweight and those on 5 kg DM/ewe/day gained throughout. Other groups were offered low allowances during summer and then 5 kg DM/ewe/day after the first recorded oestrus. Mean dates for synchronised oestrus were 2 March, 19 March and 5 April. Ovulation rate increased by 0.15 corpora lutea/ewe ovulating at each successive oestrus, and increased by 0.047 corpora lutea/ewe ovulating for each kg increase in liveweight at oestrus. These effects accounted for 77% of the variation in ovulation rate between treatments across years. The effects of flushing, lactation or summer liveweight change were small and generally non-significant. Lactation feeding affected wool growth during lactation as well and had carryover effects through the summer when lactation low ewes grew 10% less wool irrespective of the level of summer feeding.