Published online by Cambridge University Press: 27 March 2009
Sixteen Blackface wether lambs (25–27 kg) were fed for 9 weeks on diets based on either barley (B) or sugarbeet pulp (S), with either a low or high protein content. A constant amount of metabolizable energy (ME) was given at twice maintenance level. At one stage the animals were fed frequently and blood was sampled over a 24 h period. Plasma was assayed for acetate, glucose and insulin. After slaughter, the metabolism of acetate to CO2 and lipid was investigated in perirenal adipocytes in vitro.
Frequent feeding helped to achieve near-steady-state conditions. Carbohydrate source influenced plasma acetate (P < 0·08) but not glucose or insulin. Level of protein in the diet influenced plasma acetate, higher concentrations of acetate were associated with lower levels of protein (P < 0·01). Acetate oxidation and incorporation into lipid was influenced by the concentrations of acetate, glucose and insulin in the incubation media (P < 0·001). Acetate oxidation was influenced by carbohydrate source (P < 0·05), whereas level of protein in the diet affected acetate incorporation into lipid (P < 0·05).
These results show how the balance of nutrients provided to a ruminant for metabolism may influence selected plasma parameters and the metabolism of acetate by adipose tissue, which may help to explain the reduced efficiency of ME utilization from more fibrous diets.
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