Relative to an industry Romney control line, three lines derived from screening for high prolificacy, consisting of Romneys, Perendales and Coopworths had significantly heavier weaning weights after adjustment for non-genetic factors with weights of 19.9 (100), 22.3 (112), 24.0 (121) and 23.9 (120) kilograms (percentage relative to the Romney controls) for the respective flocks. The differences increase post-weaning and when slaughtered, between 175 and 219 days of age, the carcass weights (kg) were 12.0 (100), 14.3 (119), 16.1 (134), 15.7 (131) respectively for the different strains. Although the base populations of Romneys are not genetically comparable the results suggest that the intensive screening for prolificacy has indirectly resulted in animals capable of more rapid growth to slaughter. The differences between strains in their carcass weight adjusted subcutaneous fat depths were minor except that the high prolificacy Perendales had lower increases in fat depths with increasing carcass weight and had the lowest subcutaneous fat depths at heavy weights. Additionally the high prolificacy Perendales had 2 to 6 percent larger estimated L. dorsi areas than the other genotypes.

AJ, Litherland, DJ Paterson, AL Parry, HB Dick, and LD Staples

Proceedings of the New Zealand Society of Animal Production, Volume 50, , 339-344, 1990
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