Biometric properties of lactations in ewes raising single or twin lambs

Abstract

The lactation curves of 21 single- (SR) and 28 twin-rearing (TR)ewes were fitted and milk production was estimated by the model Y = ax^b e^−cx, developed in England for dairy cattle. In addition, persistency of lactation of SR and TR ewes was compared using five procedures reported in the literature. Results indicated that the coefficients that characterize the shape of the lactation curve (b and c values) were of similar magnitude to those reported in dairy cattle, thus denning a curve of similar shape. Lactation curves of SR and TR ewes were essentially parallel throughout lactation, with more milk production from TR ewes. The correlation between total milk production estimated by this model and that based on the sum of partial lactations was 0·98, but variability of milk production as estimated by the latter method was slightly less. Lactations of SR ewes had similar persistency to those of TR ewes.