In a series of studies, relationships between herbage allowance (as measured by sward surface height (SSH), herbage intake (measured by intraruminal chromium controlled release capsule) and production were assessed in continuously stocked winter (June)- and spring (August)- lambing pregnant and lactating ewes. At SSHs of 2.8, 4.0, 7.1 and 8.5 cm, organic matter intakes (OMI) of winter-lambing ewes in the last month of pregnancy were 1.4, 1.7, 1.6 and 1.9 (Pooled SE = 0.1) kg/d (P<0.05), respectively. Ewe liveweight gain over the last month of pregnancy increased with SSH but there was no effect of SSH on lamb birthweight or ewe midside wool growth. Similarly, pregnant spring- lambing ewes had OMI of 1.4, 1.7, 1.8 and 1.9 (PSE = 0.1) kg/d (P<0.05) at SSHs of 2.7, 4.0, 5.9 and 7.8 cm, respectively and ewe liveweight gain increased with SSH but there was no effect of SSH on ewe wool growth or lamb birthweight. Results suggest that both winter- and spring-lambing ewes can tolerate SSH below 3 cm during late pregnancy without detrimental effects on lamb or wool production. Winter-lambing lactating ewes (first two months of lactation) had OMI of 1.8, 2.3 and 2.5 (PSE = 0.1) kg/d (P<0.05) at SSHs of 2.6, 4.4 and 7.8 cm respectively. Sward height did not influence ewe wool production or lamb growth but ewes on the 2.6 cm sward lost 8-10 kg more liveweight during lactation than those on the 4.4 and 7.8 cm swards. Spring- lambing ewes had OMI of 1.8, 2.0, 1.9, 2.0 and 2.0 (PSE = 0.3) kg/d (P<0.1) at SSHs of 3.5, 5.0, 6.0, 7.0 and 8.5 cm, respectively. There were no effects of SSH on ewe wool growth or lamb growth but ewe liveweight loss was greatest at low SSH. Results are discussed in the context of feeding recommendations for winter- and spring-lambing ewes.
Proceedings of the New Zealand Society of Animal Production, Volume 52, , 285-288, 1992
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