Glucose metabolism and adrenal function in goats bred for fibre production (Angora goat) or meat production (Boer goat)

Author: P.B. Cronjé
Year: 1992
Issue: 5
Volume: 22
Page: 149 - 153

It has been proposed that the abortions, cold-stress fatalities, and slow growth rates typical of the South African type of Angora goat can be explained by congenital adrenal hypofunction incident to genetic selection for hair production. The aim of this experiment was to compare glucose metabolism and adrenal function in Angora goats vs. Boer goats under a range of dietary conditions. Glucose plasma concentration was 7% lower in Angoras (P < 0.01). Glucose flux rate was increased by dietary level (P < 0.01), and there was an interaction between breed and diet (P < 0.05). The rate of increase in glucose flux rate with increasing dietary energy level was slower in Angoras. The amount of glucose in the metabolic pool was 8% more in Angoras (P < 0.05), and this was distributed throughout a 17% larger volume of body fluid (P < 0.01). Both pool size and volume of distribution increased (P < 0.05) with level of feed. Glucose clearance rate did not differ between breeds (P > 0.05), and there was no evidence of impaired adrenal function in Angora goats following glucose loading. Acetate clearance rate was 20% slower (P < 0.01) in Angora goats. There was a positive linear (P < 0.05) relationship between acetate clearance rate and diet, but no interaction (P > 0.05) between breed and diet. Although much of the data reported is consistent with impaired gluconeogenic capability, no evidence of adrenal hypofunction could be found. It was concluded that a more likely hypothesis would be that selection for hair production has resulted in a shift in the partitioning of amino acids away from gluconeogenesis towards hair-protein synthesis to the extent that the Angora goat may be unable to mobilize sufficient endogenous protein reserves rapidly enough for gluconeogenesis during times of sudden demand.


Keywords: Acetate, adrenal, glucose, goat, metabolism, nutrition, ruminant, selection
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