Colostrum production and hormone responses of parturient ewes fed varying amounts and types of supplement

Abstract

Low perinatal lamb loss and fast lamb growth rates are important measures for efficient sheep production. To understand the role of ewe nutrition in late pregnancy, 100 adult Border Leicester × Merino ewes were joined at a synchronised oestrus. Ewes were nutritionally managed to maintain maternal body condition until day 130 of pregnancy at which time 50 twin-bearing ewes entered single pens. Thirteen ewes were allocated as controls and 14, 11 and 12 ewes for the 3 treatments groups. All were fed a base diet of lucerne hay (17.3% crude protein; 9.4 MJ ME/kg DM). Three of the 4 treatment groups were supplemented with oaten grain, formaldehyde-treated sunflower meal or lupin grain at 1 of 3 nominal feeding levels: 250, 500 or 750 g/ewe.day of supplement. Actual intake was less than amounts offered. Intakes measured in the final 5 days prepartum, were used in the analysis. Data were collected on peripheral progesterone and insulin-like growth factor-1 at 4 days prepartum and 50 min postpartum; peripheral oestrone sulfate at 4 and 3 days prepartum and 50 min postpartum; and colostrum weight and score at 50 min postpartum. Feeding level of supplement, but not type of supplement, significantly increased insulin-like growth factor-1 and decreased progesterone and oestrone sulfate levels. Correlations of energy and nitrogen intake with insulin-like growth factor-1, progesterone and oestrone sulfate levels were positive (P<0.01), as were the correlations of colostrum weight with these traits. An unexpected high correlation between energy and nitrogen intake masked any differential effects on colostrum production and hormone response. Nevertheless, the supply of energy and protein supplements were associated with elevated colostrum weights and scores, and lower progesterone concentration. Lowering progesterone levels is considered necessary for successful parturition. Oaten grain was the least desirable grain supplement. These observations support the practical importance of providing adequate nutrition in late pregnancy and its effect on colostrum yield and presumably lamb survival and growth.