Differential feed intake responses to central corticotrophin releasing factor in lines of chickens divergently selected for low or high body weight.

Effects of intracerebroventricular (ICV) injection of corticotrophin releasing factor (CRF) on feed intake were evaluated in two lines of White Plymouth Rock chickens that have been selected from a common base population for high (HWS) or low (LWS) juvenile body weight. Both lines responded with reduced feed intake after ICV CRF; however, the threshold of response was lower in line LWS than HWS. Additionally, the effects of two receptor antagonists, astressin and alpha-helical CRF (9-41; alpha-CRF), and the effect of CRF fragment 6-33, (which displaces CRF from its binding protein), were evaluated in these lines. Although all three antagonists increased feed intake in line LWS but not line HWS, they attenuated the appetite-reducing effects of CRF only in line HWS. Peripheral plasma corticosterone concentrations after an acute stressor were higher in line LWS than in line HWS. These data support the thesis of correlated responses in the CRF system to selection for high or low juvenile body weight. These differences may contribute to differential feed intake, and hence altered body weights.

Differential autonomic nervous system response in obese and anorexic chickens (Gallus gallus).

Effect of reserpine on body weight (BW), feed intake (FI), brain and plasma catecholamine and indoleamine concentrations in high- (HWS) and low- (LWS) weight selected lines of chickens was investigated. Chicks from each line were assigned to three treatment groups and injected intraperitoneally with 0, 1.25, or 2.50 mg/kg of reserpine at hatch, and again at 5 weeks-of-age. Chick BW and FI were determined weekly. At 7 weeks-of-age, 12 males and females from each group were sacrificed for neurotransmitter analysis. In the HWS line there was a dose-dependent decrease in BW through 7 weeks-of-age, whereas in the LWS line BW decreased only through the first 2 weeks-of-age. In the LWS line, norepinephrine (NE), epinephrine, and 3,4-dihydroxyphenylacetate concentrations decreased in the brain in a linear and quadratic manner in response to reserpine, but not in the HWS line. Both lines showed linear decreases in dopamine levels in response to reserpine; however, serotonin was not affected by reserpine. Chickens in the HWS line had greater plasma NE, and lower 5-hydroxyindoleacetic acid than those in the LWS line. In conclusion, it appears that chickens from the HWS line were more sensitive to the BW reducing effects of reserpine than those from the LWS line, with the latter appearing to have greater sympathetic nervous system activity.

Leptin effects on food and water intake in lines of chickens selected for high or low body weight.

There is an association between autonomic nervous system output and obesity. The sympathetic nervous system stimulates lipid metabolism and regulates food intake and, hence, body weight. Leptin, produced by adipocytes in proportion to their size, has been shown to directly stimulate the satiety center. In the experiment reported here, food and water intake were compared after intracerebroventricular administration of human recombinant leptin to lines of chickens that had undergone divergent selection for over 45 generations from a common White Rock base population for high (HWS) or low (LWS) body weight at 8 weeks-of-age. Leptin caused a linear decrease in food intake in chickens from the LWS line whereas no effect was observed in those from the HWS line. The HWS chickens tended to have reduced water intake post leptin administration. Others reported that leptin decreased food intake in both broiler and Leghorn chickens. Leptin concentration in the central nervous system may not contribute directly to the difference of body weight between HWS and LWS chickens.