Effect of selection for glucose tolerance in sheep on carcass fat and plasma glucose, urea and insulin

Abstract

SummaryOver 5 years (1987–91), the progeny of rams selected for fast (Low T-half) or slow (High T-half) glucose clearance after an intravenous glucose tolerance test, differed significantly in glucose tolerance. In comparison with an unselected control, the line differences were mainly in the direction of Low T-half. They appear to have arisen during the establishment period, with little evidence of enhanced divergence over the four subsequent years of continued selection (heritability 0·10±0·03). The Low line had higher plasma insulin concentrations during the glucose tolerance test than the High line. Basal plasma concentrations of glucose were lower, and urea higher in the Low than the High line. In addition, carcasses of Low line ram progeny had more subcutaneous fat at the same carcass weight than High line carcasses (11% higher GR in the final year of the experiment). Selection of sheep for glucose clearance appeared to be associated with differential partitioning of nutrients into adipose tissue, the pooled genetic correlation between T-half and GR being −0·28±0·13.