Liveweight gain of sheep grazing lucerne, lucerne/grass mixes and lucerne supplemented with barley grain

Abstract

Animal production has proved superior from lucerne than other pastures in dryland situations. There is interest to include lucerne in a mix with grasses with complimentary growth patterns. Recently there has also been unpublished claims that liveweight gains on lucerne can be improved with grain supplementation. Experiment 1 was established at Ashley Dene in 2012/13 to compare liveweight production of sheep grazing lucerne, lucerne/brome and lucerne/cocksfoot mixes. In 2013/14 lucerne plus grain supplementation was added as Experiment 2. Over the 2013/14 season in Experiment 1, sheep grazing lucerne monocultures produced 808 kg LWT/ha, compared with 642 kg LWT/ha from lucerne/brome pastures and 605 kg LWT/ha from lucerne/cocksfoot pastures. In Experiment 1, 100% of the liveweight accumulated was from lambs. Spring liveweight production accounted for over half of the total annual production. Accumulated herbage dry matter yields were ~15 t/ha/y for all treatments in Experiment 1. All pastures used 837 mm of water at an efficiency of 18 kg DM/ha/mm and grew at 4.5 kg DM/ha/oCd. Differences in lamb production in Experiment 1 were due to botanical compositions of the pastures which affected the energy available and consumed by animals. The lucerne component of lucerne/grass mixes reduced from an average 36.1% pre-grazing to 16.2% post grazing which was predominantly stalk. The grass component reduced from 33% pre grazing to 26% post-grazing which indicated a selection pressure towards lucerne. There was no difference in total annual ME produced by pastures among treatments. The selection towards lucerne shown in animals grazing lucerne/grass mixes resulted in a reduced intake of available ME due to less lucerne in the mixes (36%) than the monocultures (57%). This explained the differences in liveweight production. Animals grazing lucerne selectively grazed the leaf portion of the plant and avoided the stems which resulted in a build-up of dead material in all treatments. Using a second class of stock to follow after the lambs and graze the pastures to lower residuals could increase the utilisation of pastures and reduce the build-up of dead material. In Experiment 2, grain supplementation had no influence on lamb liveweight production, but advantages were seen in ewes. Ewes with access to barley grain gained 13 kg LWT/ha compared with ewes on the –grain treatment which lost 15 kg LWT/ha during the lactation phase. Over 80% of the grain fed occurred ii before weaning which suggested ewes were consuming the majority of the grain. The lack of grain effect on the lambs was due to a lack of uptake of grain. Pastures on both grain treatments accumulated ~12 t DM/ha during the spring and summer when Experiment 1 occurred, this suggested no substitution occurred. Benefits may be seen in lambing from the ewes supplemented with grain due to increased condition at mating. Further measurements in the coming 2014/15 season are required, to confirm this.