Mj. Linington et al., THE PLASMA COMPOSITION OF KARAKUL-LAMBS FED ISOCALORIC HIGH-FIBER ANDLOW-FIBER DIETS, South African journal of animal science, 26(3-4), 1996, pp. 79-84
Blood samples were withdrawn once weekly from the jugular vein of 10 k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.