Heritability of Gain of Lambs Measured at Different Times and by Different Methods

Abstract

Data were collected on 671 crossbred milk lambs contained in 31 sire progeny groups over a 4 year period. Lambs were sired by purebred Dorset rams and their dams were grade Rambouillet and Rambouillet x Panama-Rambouillet ewes. Rate of gain was calculated as average daily gain and weight per day-of-age. Heritability estimates were calculated by the paternal half-sib correlation method. The resulting heritability estimates for rate of gain from birth to approximately 50 lb. ranged from 0.09 [plus or minus] 0.07 to 0.13 [plus or minus] 0.08. The estimates for rate of gain from approximately 50 to 90 lb. were 0.38 [plus or minus] 0.13. Heritability estimates for rate of gain from birth to market weight of approximately 90 lb. ranged from 0.34 [plus or minus] 0.13 to 0.36 [plus or minus] 0.12. The results of this study indicate that the method of measuring rate of gain has little effect on the heritability estimate. Likewise, when birth weight was deleted from the model, the resulting heritability estimate was approximately the same as the estimate calculated when birth weight was included in the model as a co-variable.