Effect of Heat Exposure on Gene Expression of Feed Intake Regulatory Peptides in Laying Hens

The aim of this paper was to investigate the effect of heat stress on the regulation of appetite-associated genes in laying hens. Forty eight laying hens were randomly divided into two circumstances: high (31 +/- 1.5 degrees C; relative humidity, 82.0 +/- 2.2%) or normal (20 +/- 2 degrees C, control; relative humidity, 60.1 +/- 4.5%) ambient environment. Heat stress decreased body weight gain (P < 0.01), feed intake (P < 0.01), laying rate (P < 0.05), average egg mass (P < 0.01), egg production (P < 0.01), shell thickness (P < 0.01), and feed efficiency (P < 0.05). High ambient temperature decreased plasma uric acid (P < 0.05). Heat stress significantly increased mRNA levels of ghrelin and cocaine-and amphetamine-regulated transcript (P < 0.05) and decreased mRNA levels of cholecystokinin (P < 0.05) in the hypothalamus. Heat stress significantly increased (P < 0.05) mRNA levels of ghrelin in the glandular stomach and jejunum but significantly decreased (P < 0.05) mRNA levels of cholecystokinin in the duodenum and jejunum. In conclusion, heat stress plays a unique role in some special neuropeptides (e.g., ghrelin, cocaine-and amphetamine-regulated transcript, and cholecystokinin), which might participate in the regulation of feed intake in laying hens under high ambient temperature.