The effect of winter shearing of housed pregnant ewes on food intake and animal performance

The effects of winter shearing on the food intake and performance of housed ewes was studied in a series of three experiments. Winter shearing resulted in a proportional increase of dry-matter intake in ewes of 0·16 and 0·43 on two silage-based diets, of 0·09 on swede-based diets, but of only 0·02 on a hay-based diet. Shearing increased intake by a greater amount in smaller ewes and a similar trend occurred on diets containing a greater proportion of barley. Shearing increased average lamb birth weight by about 600 g (4·65 kg v. 4·06 kg), apparently as an effect of shearing per se rather than as a result of the increased energy intake. An increase in gestation length of around 1·8 days accounted for one-fifth of this increased birth weight. The effect on gestation length of shearing was to increase the unnaturally short gestation of housed unshorn ewes, this short gestation being attributed to problems of heat stress in late pregnancy. Results indicated management advantages of winter shearing in favourable climatic environments.