Although food intake regulation by the central nervous system in the fowl has received considerable attention, studies examining peripheral regulatory mechanisms are relatively few. The objective of these experiments was to determine the role of the liver in short-term regulation of feeding. Small volumes of isotonic glucose were infused into the hepatic circulation of undisturbed, unrestrained Single Comb White Leghorn (SCWL) and Rock-Cornish (RC) cockerels under both free-feeding and mildly-fasted conditions. Glucose infusions significantly decreased the food intake of free-feeding SCWL chicks but had no effect on mildly-fasted SCWL chicks. The RC chicks, whether free feeding or mildly fasted, were not influenced by the glucose infusions. These findings suggest that selection for increased growth rate has affected peripheral appetite regulatory mechanisms.

Two experiments, which differed in breeder age, strain and season, were conducted to study the influence of low-intensity, short-duration thermal stimuli during the late phase of incubation on hatchability and performance. The first experiment conducted in April-June used eggs from Cobb × Ross broiler breeders at 35-41 weeks of age and the second experiment performed in February-April used eggs from Hubbard × Cobb broiler breeders at 49-53 weeks of age. Eggs in the test group had the same physical environment as eggs in the control group except that incubation temperature was increased by 1˚C for 2 h/d above the control group from 18 to 20 d of incubation (DI). The results demonstrated that thermal stimulation of 1˚C for 2 h/d above control incubation temperature during 18-21DI did not have any adverse effects on hatch and post-hatch performance of broilers. In both experiments, treatment did not significantly alter the secondary sex ratio in hatched chickens, but hatch residue showed that the proportion of unhatched male embryos was significantly lower in the test groups than in the control groups. In the first experiment, thermal stimulation improved feed conversion by 1.82% compared with the control.

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