Effect of sward height on herbage intake and production of ewes of different rearing rank during lactation

Publisher Website
Google Scholar
Abstract
Groups of six single- and six twin-rearing ewes were continuously stocked on five pastures with sward surface heights (SSHs) of 3·5, 5·0, 6·0, 7·0 and 8·5 cm from week l until week ll of lactation. Herbage intake, estimated from faecal chromium concentrations and thein vitrodigestibility of herbage samples collected from oesophageal-fistulated wethers, was lowest on the 3·5 cm sward but was not significantly different between SSH treatments during weeks 5, 8 and 9 of lactation. Twin-rearing ewes consumed 0·9–17·6% more herbage than single-rearing ewes did. By week ll, ewe liveweights showed increases of 2–4 kg/ewe on all except the 3·5 cm sward, where the ewes lost a similar amount of liveweight. From week 4 of lactation, twin-rearing ewes had a lower body condition than ewes raising a single lamb on all except the 3·5 cm sward, where the body condition of both rearing ranks was similar. Lamb growth rates during the first 6 weeks were similar for each SSH treatment but from days 46–76 of lactation, lambs on the 5·0 cm and longer swards grew faster (240 g/day) than those on the 3·5 cm sward (197 g/day). Lamb weight on day 76 ranged from 21·5 kg on the 3·5 cm sward to 23·0 kg on the 5·0 cm sward, but was not significantly affected by SSH. Similarly, midside wool growth of ewes and lambs was not significantly influenced by SSH during the period of continuous stocking. The results indicate that farmers should aim to provide swards of 5–7 cm height during lactation to maximize production in both single- and twin-rearing ewes.