Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 18 EFFECT OF DOSE LEVEL OF BOVINE SOMATOTROPIN ADMINISTERED TO MERINO EWES DURING LATE PREGNANCY AND EARLY LACTACTION M.J. WATSON*, R.M. DIXON**, R. THOMAS** and A.R. EGAN** One possible means of manipulating the partitioning of nutrients aud the mobilization of body tissues of ekes in late pregnancy and early lactation is The following experimept by the administration of exogenous growth ho-ne. was undertaken to examine the effects of various dose levels of bovine somatotropin (BST) on ewes fed a concentrate diet. Single bearing Merino ewes (44 to 64 kg live weight (LW), 2+ to 4 condition score) were, commencing six weeks before parturition, housed in single pens and The diet consisted, on an air dry basis, of 700 g of fed a concentrate diet. 85% whole wheat grain, 15% whole lupin grain and minerals plus 50 g pasture hay until parturition, and following parturition the same diet except that the Commencing 21 d before expected concentrates were given ad libitum. parturition, and until 21 d after parturition, placebo (NaHCO, buffer) or each of three levels of BST (2.5, 5.0 or 10.0 mg/d) were administered by subcutaneous injection. Measurements were made of feed intake, LW of ewes and lambs, colostrum and milk output (by milking following oxytocin administration) at 7 d intenrals and growth hormone concentration in the plasma of ewes. Measurements were continued until 42 d after parturition. Table 1 Responses of ewes at various times after parturition administration from 21 d before parturition until 21 parturition to BST d after The results (Table 1) indicate that although not statistically significan\t, there was a tendency for the 5.0 mg BST/d to increase feed intake, milk DM output and lamb LW gain compared with the control, both during and following BST administration. The level of 10.0 mg BST/d tended to increase milk DM output at d 1, and to result in milk DM output and lamb growth similar to the 5 mg BST/d dose during administration. However, after termination of BST these values tended to be lower than for the 5 mg BST/d dose level. * ** Research Vic. School of Vic. Institute, Department of Agriculture and Rural Affairs, Werribee, 3030. Agriculture and Forestry, The University of Melbourne, Padwille, 3052. 566
