DIFFERENCES IN GLUCOSE RESPONSE TO INSULIN STIMULATION AND FASTING BETWEEN ANGORA-GOATS OF 2 DIFFERENT PHENOTYPES

The aim of this study was to investigate suggestions that the high incidence of abortions and cold stress fatalities in Angora goats is due to an anomaly in glucose homeostasis brought about by selection for high levels of mohair production. Fifty-nine bucks of a large phenotype which produces a relatively large amount of mohair of a large fibre diameter (high producers) were compared to 56 bucks of a smaller phenotype which produces less mohair of a smaller fibre diameter (low producers). Basal plasma glucose concentrations were determined on two occasions: prior to intravenous injection of insulin and prior to a 48 h fast. In both instances concentrations were 6-9% lower in high producers. High producers took 22% longer to restore glucose concentration to basal levels following insulin injection, and glucose concentrations declined 28% more rapidly during fasting. The results indicate that the high producing phenotype is characterized by an inability to mobilize glucose precursors during periods of increased demand, and it was suggested that this may be related to the high incidence of abortions and cold-related deaths reported among Angoras. There was no correlation between any of these parameters and fibre growth rate, and it was concluded that the physiology of animals selected under conditions where natural fluctuations in nutrient supply are abridged by supplementary feeding may have changed to favour nutrient partitioning towards hair production at the expense of labile body protein reserves.