Stocking rate joining time fodder conservation and the productivity of merino ewes part 2 birth weight survival and growth of lambs

Egan, J.K.; Thompson, R.L.; Mcintyre, J.S.

Australian Journal of Experimental Agriculture and Animal Husbandry 17(89): 909-914


Accession: 006484430

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In an experiment at Hamilton in western Victoria [Australia] groups of 30 Merino ewes were stocked at 11.7, 15.4 or 19.2 ewes ha-1 and joined to Merino rams each year on April 5 or May 8 for 5 wk. Hay was conserved on half the number of plots and fed back to the ewes before and during joining. Observations on birth weight, survival and growth of lambs born between 1970-73 are presented. Both the highest stocking rate and the earlier lambing were associated with a depression of about 7% in the birth weight of twin lambs, but single lambs had similar birth weights on all treatments. Lamb survival was highly variable and there were few significant treatment effects. Mortalities within 48 h of birth were lower among flocks joined to lamb in Oct. than those lambing in Sept. (single lambs 9.2% vs. 14.7%, twin lambs 19.9% vs. 40.2%). Most of the improvement was attributed to drier conditions and lower windspeeds in Oct. Lamb growth rates fell with increasing stocking rate but the variation in weaning weight was less than 2 kg. Lambs born in Sept. were about 10% heavier at weaning than those born in Oct. Compensatory growth after weaning resulted in negligible differences in weight at 12 mo. between lambs from the different stocking rate treatments, but lambs born in Sept. were still significantly heavier than those born in Oct.