The effect of nutritional supplements in late pregnancy on ewe colostrum production plasma progesterone and IGF-1 concentrations

Abstract

Mechanisms by which nutritional supplementation might improve colostrum production and enhance lamb survival were examined in adult Border LeicesterxMerino ewes. Ewes were either unsupplemented or supplemented with 500 g/day of oat grain, lupin grain or a formaldehyde-protected sunflowerseed meal (SFM) from day 130 of gestation until parturition while grazing spring pastures containing about 1000 kg green DM/ha. Blood samples were obtained on day 140, day 145 and immediately after parturition. Colostrum production at parturition and for the next 6 h was determined. A new method to determine concentrations of insulin-like growth factor-1 (IGF-1) is presented. Colostrum production at parturition (P.< 0.01) and IGF-1 concentration on day 140 (P.< 0.01) and at parturition (P.< 0.001) were higher, and progesterone concentrations on days 140, 145 and at parturition were lower (P.< 0.001) for single than twin bearing ewes. The unsupplemented ewes and ewes fed oat grain, lupin grain or SFM had an average weight of colostrum at parturition of 292, 328, 452 and 392 g (P.< 0.01), milk secretion rate to 6 h after parturition of 58, 64, 85 and l00g DM/h (P.< 0.05), IGF-1 concentrations after parturition of 199, 223, 262 and 265 ng/mL (P.< 0.001) and progesterone concentrations on day 140 of 49, 43, 39 and 41 nmol/L (P.< 0.01) respectively. Twin compared to single bearing ewes had about half the amount of colostrum at parturition per kg of lamb birthweight. Progesterone concentrations on day 140 and at parturition (P.< 0.01) were negatively related to estimated pasture intake during pregnancy, which was 17% higher for single than twin bearing ewes (P.< 0.05). Supplementation with lupins and SFM may be expected in similar circumstances to enhance the survival of multiple born lambs, while oat grain would not.