A period of energy supplementation but not the type of supplement influences the insulin response to exogenous glucose in food-restricted post-partum suckler beef cows

Abstract

AbstractTwo experiments were designed to study the influence of an increase in energy supply on the utilization of exogenous glucose in food-restricted post-partum Charolais suckler beef cows. In experiment 1, 18 cows were given a basal diet (BD) providing 0·70 of energy requirements from calving with or without an energy supplement (SD) of 2 kg of rolled triticale grain starting at day 32 post partum. On day 42 post partum an injection of glucose (1·0 mmol/kg live weight) lasting 20 min resulted in a similar plasma glucose and cortisol profile in each diet group but a smaller plasma insulin increase in SD than in BD cows (146 (s.e. 37)v.273 (s.e. 37) pmol/l,P< 0·05). Plasma non-esterified fatty acids concentrations were reduced by the glucose injection (P< 0·01). Experiment 2 compared the efficiency of an energy supplement in the form of concentrate (CS, maize grain, no. = 11) or forage (PS, maize silage, no. = 10) in oestrous-synchronized beef cows previously given a restricted diet. Glucose injection resulted in a small increase in insulin concentrations during infusion with a peak at 20 min (PS: 250 (s.e. 34)v.CS: 257 (s.e. 32) pmol/l,P> 0·05). No differences were observed between the two groups of cows for glucose, insulin and cortisol profiles (P> 0·05). Similar pregnancy rates after oestrous synchronization treatment were observed in CS and PS cows (6/11v.5/10). In conclusion, a period of supplementation sufficient to re-establish energy balance, but not the type of supplement, influences the insulin response to exogenous glucose in food-restricted post-partum Charolais beef cows.