Diet-induced thermogenesis in cockerels is modulated by genetic selection for high or low residual feed intake.
Energy balance of adult cockerels genetically selected for high (R+) or low (R-) residual feed consumption was investigated by using indirect calorimetry. Although no between-line difference was found in digestion of ingested energy, the true metabolizable energy (ME) intake was 40% greater in R+ than in R- birds. Basal heat production (HP) did not significantly differ between genotypes. Diet-induced thermogenesis (DIT) was significantly enhanced in R+ compared with R- birds, i.e., +84% when expressed as the difference in kilojoules of heat production determined in feed-deprived and fed cockerels, +31% when calculated as a percentage of ME intake (P < 0.01). The difference in DIT calculated from the regression between HP and physical activity explained 75% of the difference in HP; the remaining 25% could be explained by activity-related HP. The results cannot be explained by differences in the plasma concentration of circulating thyroid hormones: plasma thyroxine concentration did not differ between genotypes, whereas plasma triiodothyronine concentration was lower in feed-deprived R+ than in R- birds and indistinguishable in fed birds of the two lines. Heat production, however, was higher in the R+ line. Propranolol decreased HP only in the R+ line, suggesting a beta-adrenergic control of DIT at least in cockerels of this line. Plasma triglyceride concentration was lower in the R+ than in the R- line in fed cockerels, and plasma nonesterified fatty acid concentration was higher in the R+ than in the R- line in feed-deprived cockerels. These results are consistent with the leanness of the R+ compared with the R- line. The R+ and R- lines constitute an original model of diet-induced thermogenesis (DIT), a process that is under genetic control of appetite and allows R+ birds to balance all of their excessive energy intake without any adipose tissue storage.
Gabarrou
J F
JF
Station de Recherches Avicoles, INRA, 37380 Nouzilly, France.
Géraert
P A
PA
Picard
M
M
Bordas
A
A
D000818:Animals; D001066:Appetite / Q000235:genetics; D001786:Blood Glucose; D001833:Body Temperature Regulation / Q000235:genetics* / Q000502:physiology; D002645:Chickens; D004032:Diet; D004435:Eating / Q000235:genetics* / Q000502:physiology; D002149:Energy Intake; D008297:Male; D005082:Physical Exertion; D013963:Thyroid Hormones / Q000097:blood; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D013963:Thyroid Hormones; D014280:Triglycerides