Estimation of correlations between ewe litter size and maternal effects on lamb weights in Merino sheep

Abstract

Data corresponding to weights from birth to 90 days of age of 4 425 lambs, and to 3 355 litters at lambing of 964 ewes, taken from 1987 to 1995 were used. The main objective of the study was to quantify the possible relationship between litter size of the ewes and their maternal effects on offspring weights. The results showed that the additive genetic correlation between litter size and the maternal component of weight is zero. The additive genetic correlation was low between litter size and the direct component of weight, and was similar to the correlation between permanent environmental effects for litter size and maternal permanent environmental effects for weights. In view of the results obtained, no complication should be expected if the local Merino breed could be oriented to the production of high quality females (improving their litter size and maternal abilities) to be used in terminal crosses for lamb meat production.