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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°C; relative humidity, 82.0 ± 2.2%) or normal (20 ± 2°C, control; relative humidity, 60.1 ± 4.5%) ambient environment. Heat stress decreased body weight gain ( 𝑃 0 . 0 1 ), feed intake ( 𝑃 0 . 0 1 ), laying rate ( 𝑃 0 . 0 5 ), average egg mass ( 𝑃 0 . 0 1 ), egg production ( 𝑃 0 . 0 1 ), shell thickness ( 𝑃 0 . 0 1 ), and feed efficiency ( 𝑃 0 . 0 5 ). High ambient temperature decreased plasma uric acid ( 𝑃 0 . 0 5 ). Heat stress significantly increased mRNA levels of ghrelin and cocaine- and amphetamine-regulated transcript ( 𝑃 0 . 0 5 ) and decreased mRNA levels of cholecystokinin ( 𝑃 0 . 0 5 ) in the hypothalamus. Heat stress significantly increased ( 𝑃 0 . 0 5 ) mRNA levels of ghrelin in the glandular stomach and jejunum but significantly decreased ( 𝑃 0 . 0 5 ) 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.
Song et al. (Sun,) studied this question.