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

An on-farm demonstration compared the use of perennial ryegrass based pasture or lucerne as the forage source for in-lamb ewe lambs from two weeks prior to lambing until weaning in the Te Anau basin. This demonstration, over two 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. Stocking rates were chosen based on previous pasture growth records and potential lucerne yield. The liveweight and body condition score of ewe lambs was measured. Lamb liveweight were recorded at docking and weaning. Records were kept of grazing events and both ewe and lamb losses and their potential causes. 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 on the lucerne (11.7 ewes/ha) was greater than that on pasture (9.4 ewes/ha). Lamb weaning weights were similar from the pasture and lucerne. Ewe lamb live weights and BCS tended to be higher when grazed on lucerne during the spring and all ewe lambs were at or near 2th mating weights at weaning. The combined liveweight gain of ewe lambs and their lambs per hectare was significantly greater from lucerne (492 kg/ha) than pasture (398 kg/ha). 2 tooth scanning data after the 2013 lambing was 204% in ewes that grazed on lucerne during lactation compared with 187% on ewes that had grazed on pasture during lactation. This difference occurred even though the 2 tooth mating weights were only 2 kg different between groups at an average of approximately 65 kg. Lucerne can be used as a forage option to increase the performance of bred ewe lambs but care must be taken to ensure that the grazing rules for lucerne are met to reduce potential animal health issues.