Effect of bovine somatotropin administration during late pregnancy and early lactation on Merino ewes given low or high planes of nutrition during pregnancy.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 18 EFFECT OF BOVINE SOMATOTROPIN ADMINISTRATION DURING LATE PREGNANCY AND EARLY LACTATION ON MERINO EWES GIVEN LOW OR HIGH PLANES OF NUTRITION DURING PREGNANCY R.M. DIXON*, M.J. WATSON**. R. THOMAS*, C.J. REID** and A.R. EGAN* The partition of nutrients and mobilisation of body tissues of ewes in late pregnancy and early lactation may be influenced by both the amounts of body tissues available for mobilization and the administration of exogenous growth hormone. The following experiment was undertaken to examine these effects and their interaction in ewes fed a concentrate diet, Single bearing Merino ewes were divided at random into two groups 60 d after joining, and low and high planes of nutrition were imposed by pasture availability and quality. Six weeks before parturition the ewes were housed in single pens and fed a concentrate diet as described by Watson et al. (1990) except that before parturition high plane of nutrition ewes were fed an From 21 d prior to expected parturition and additional 400 g/d of lupins. until 21 d after parturition, ewes within each plane of nutrition were given placebo (NaHCO, buffer) or 5 mg bovine somatotropin (BST)/d by subcutaneous injection. Table 1 Responses of ewes given low or high planes of nutrition during pregnancy to BST administration from 21 d before parturition until 21 d after parturition The results indicate that the ewes given a high plane of nutrition during pregnancy were heavier at parturition, and during early lactation lost more LW. Plane of nutrition did not affect milk output, lamb birth weight or lamb LW gain. BST administration increased ewe LW at parturition, milk output and lamb LW gain, but did not affect feed intake, ewe LW change, colostrum output or lamb birth weight. No significant BST x Nutrition interactions were observed. WATSON, M-J,, DIXON, R-M., THOMAS, R. and EGAN, A.R. (1990). Prod. 18:566. Aust. Soc. Anim. ** School of Agriculture and Forestry, The University of Melbourne, Parkville, Vic. 3052. Animal Research Institute, Department of Agriculture and Rural Affairs, Werribee, Vic. 3030. 468