THE PLASMA COMPOSITION OF KARAKUL-LAMBS FED ISOCALORIC HIGH-FIBER ANDLOW-FIBER DIETS

Blood samples were withdrawn once weekly from the jugular vein of 10 k arakul lambs (ca. 17 kg) for 12 weeks. The lambs were randomly allocat ed to a treatment and fed either a high-fibre (HF, n = 5) or low-fibre (LF, n 5) diet. Dietary carbohydrate was provided as either structura l (HF treatment) or readily fermentable (LF treatment) whereas the ene rgy and nitrogen ratios were kept constant. Blood samples were drawn o nce a week and plasma concentrations of glucose, free fatty acids (FFA ), lactate, insulin and glucagon were determined. Differences in the e fficiency of metabolizable energy utilisation were determined from the average daily intake (ADI), average daily gain (ADG) and feed convers ion ratio (FCR). ADI, ADG and FCR as well as the plasma composition re mained constant within a treatment over the 12-week period. All data w ithin each group of lambs were subsequently pooled. The ADI was higher in the HF than the LF (p less than or equal to 0.05), whereas the dig estible energy and nitrogen intakes were similar for the two treatment s. The plasma glucose and FFA concentrations were higher (p less than or equal to 0.05) in the LF than in the HF lambs. Insulin levels were higher (p less than or equal to 0.05) in the HF than in the LF lambs ( 1.39 and 1.66 +/- 0.07 ng.ml(-1), respectively). There were no differe nces in the glucagon concentrations between groups. The insulin:glucag on ratio was, however, higher (p less than or equal to 0.05) in the HF than the LF group. The LF lambs maintained a higher ADG (p less than or equal to 0.05) than the HF lambs (160 and 115 +/- 3.6 g.day(-1), re spectively) and at the same time had a lower (p less than or equal to 0.05) FCR than the HF lambs (5.9 and 10.1 +/- 0.75, respectively). The LF lambs were more efficient (p less than or equal to 0.05) at conver ting dietary energy into body mass than the HF lambs, requiring 68.9 M J ME per kg gain compared to 98.3 +/- 5.48 MJ ME per kg gain of the HF lambs.