Glucose-insulin relationships and thyroid status of cockerels selected forhigh or low residual food consumption

The plasma glucose-insulin relationships and thyroid status were investigat ed in two lines of adult cockerels divergently selected for high (R+) or lo w (R-) residual food consumption (RFC). For a given body weight, R+ birds h ad a 74 % higher food intake than R- birds. Plasma glucose concentrations w ere significantly lower in the R+ line compared with the R- when fasted, wh ereas R+ birds exhibited a significantly lower plasma insulin concentration than R- birds either in fed or fasted state. After an overnight fast, R+ b irds also exhibited a higher sensitivity to exogenous insulin in view of it s more pronounced hypoglycaemic effect. After an oral glucose load, the glu cose disposal of R+ cockerels was faster despite lower glucose-induced plas ma insulin concentration. Whilst plasma triacylglycerol concentrations were lower in the R+ line when fed, plasma non-esterified fatty acid concentrat ions were higher in fasted R+ than R- cockerels (684 v. 522 mu mol/l). High er plasma triiodothyronine concentrations were observed in fed R+ compared with R- birds (3.0 v. 2.1 nmol/l respectively). The higher plasma concentra tions of triiodothyronine associated with lower concentrations of insulin c ould account for the leanness and the elevated diet-induced thermogenesis p reviously observed in the R+ line.