Sm. Francis et al., EFFECT OF SELECTION FOR GLUCOSE-TOLERANCE IN SHEEP ON CARCASS FAT ANDPLASMA-GLUCOSE, UREA AND INSULIN, Journal of Agricultural Science, 123, 1994, pp. 279-286
Over 5 years (1987-91), the progeny of rams selected for fast (Low T-h
alf) or slow (High T-half) glucose clearance after an intravenous gluc
ose tolerance test, differed significantly in glucose tolerance. In co
mparison 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 concentra
tions of glucose were lower, and urea higher in the Low than the High
line. In addition, carcasses of Low line ram progeny had more subcutan
eous fat at the same carcass weight than High line carcasses (11% high
er GR in the final year of the experiment). Selection of sheep for glu
cose clearance appeared to be associated with differential partitionin
g of nutrients into adipose tissue, the pooled genetic correlation bet
ween T-half and GR being -0.28 +/- 0.13.