Crossbreeding for lamb production. 1. Survival and growth of first cross lambs

Abstract

The reproductive performance was studied of two groups each of 450 Peppin Merino ewes joined to Merino, Border Leicester and Dorset Horn rams in two years at the Cowra and Glen Innes Agricultural Research Stations. The survival and growth of the progeny was assessed to weaning with the wether progeny subsequently slaughtered and carcase weight and grade compared. There was little difference in the survival of lambs sired by Border Leicester or Dorset Horn rams and, for both, survival was about three per cent lower than that of Merino lambs at birth and also from birth to weaning. The single crossbred lambs were markedly heavier than the single Merino lambs at all stages of growth, but the difference between twins was considerably reduced, which gave sigrdicant breed X type of birth interactions for all growth characters examined. The Dorset X Merino lambs were 2.5 per cent heavier at weaning and had three per cent heavier carcases than the Border X Merino lambs. The heavier carcas weights for the Dorset X Merino lambs was mainly due to higher dressing percentages. There were significantly more first grade carcases amongst the crossbred than the Merino lambs, with a higher proportion of Dorset X Merino carcases in the first grade than Border X Merino.