An on-farm study of late pregnancy and lactation performance of ewe lambs and their progeny on lucerne or pasture

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An on-farm demonstration compared the use of perennial ryegrass based pasture or lucerne as the forage source for in-lamb ewe lambs from 2 weeks prior to lambing until weaning in the Te Anau basin. This demonstration, over 2 years, used 632 and 506 in-lamb ewe lambs in 2013 and 2014 respectively with approximately 50% being single-bearing and 50% twin-bearing in both years. Pasture and lucerne were set stocked until docking at approximately 33 days of age and then rotationally grazed thereafter until weaning at approximately 110 days of age. Ewe liveweights and body condition scores tended to be higher when grazed on lucerne during spring and all ewes were at or near two-tooth mating weights at weaning (67 kg). Lamb liveweights at 110 days of age were similar from the pasture and lucerne (33.4 kg). Lamb losses were greater on lucerne (37%) than pasture (28%) in both years, and led to a significantly lower lambing percentage on lucerne. Stocking rate chosen based on previous pasture growth records and potential lucerne yield was greater on lucerne (11.7 ewes/ha) than that on pasture (9.4 ewes/ha). The combined liveweight gain of ewes and their lambs per hectare was significantly greater from lucerne (492 kg/ha) than pasture (398 kg/ ha). Scanning data from the second mating was 201% and 189% in ewes that had grazed on lucerne or pasture during the previous lactation respectively, while ewes weighed 67.7 and 65.1 kg at mating respectively. Lucerne can be used as a forage option to increase the performance of bred ewe lambs but the grazing of young lush growth should be avoided to reduce potential animal health issues. Keywords: body condition score, ewe lambs, lamb liveweight gain, lamb survival, reproduction