Comparison of estimates of repeatability and heritability for some production traits in Merino rams and ewes. I. Repeatability

Abstract

Repeatabilities of 10 traits, namely, greasy wool weight, clean scoured yield, clean wool weight, body weight, wrinkle score, face cover score, fibre population density, fibre diameter, staple length, and crimps per inch, were estimated in ewes and rams. Estimates ranged from 0.4 to 0.7 for the 10 traits in both sexes. In general, body weight was the most repeatable trait and face cover the least. There is no evidence of sex differences in repeatability of the traits studied. Correlations between pairs of records obtained at different ages were high in both rams and ewes. This finding, together with the high repeatability values for all the traits, suggests that selection of sheep based on a single record is probably sufficiently accurate for lifetime performance of these 10 traits in Merinos. The correlations between yearling records and subsequent records in ram were found to be in agreement with correlations between records taken at older ages. Early selection of rams for lifetime performance therefore is probably almost as efficient as selection at a later age, and it is suggested that this finding might also be found to apply to ewes.