Heat stress-induced reduction in feed intake is an annoyance of the poultry industry. Feed intake is regulated by complex mechanisms in which brain-gut neuropeptides are involved, but the changes in such neuropeptides in broiler chickens during heat exposure remain unclear. In this study, we investigated the effects of acute heat stress (35°C, 6 h, and 65% relative humidity) on the gene expression of appetite-regulating peptides in the hypothalamus and gastrointestinal tract of broiler chickens at 42 d of age. The hypothalamic mRNA levels of neuropeptide Y, agouti-related peptide, pro-opiomelanocortin, cocaine- and amphetamine-regulated transcript, corticotropin-releasing hormone, melanocortin 4 receptor, melanin-concentrating hormone, prepro-orexin, cholecystokinin (CCK), and ghrelin did not significantly change (P>0.05) in the heat-exposed broiler chickens. However, the mRNA levels of ghrelin in the glandular stomach, duodenum, and jejunum significantly increased and the mRNA level of CCK in the duodenum significantly decreased. The results indicate that acute heat stress had no effect on the gene expression of central appetite-regulating peptides under current experimental conditions; however, some gastrointestinal tract peptides (e.g., ghrelin and CCK) might play a role in the regulation of appetite in acute heat-exposed broiler chickens. Furthermore, ghrelin in the glandular stomach, duodenum, and jejunum might be the main regulative target of acute heat stress induced anorexia.

Perching is a natural behaviour of wild and domesticated fowl. Perch availability has been used to improve the welfare of laying hens. However, the effect of perch availability on broiler rearing systems remains unclear. The present study investigated the effect of the interaction between perch availability and stocking density on the performance, behaviour, and health characteristics of broiler chickens. The behaviour, live performance, incidence of footpad and hock burn, lameness, and feather condition of the birds were investigated over a 5-week experimental period. One-day-old chicks (n = 1152) were subjected to a two (perches) × three (stocking densities) factorial design. The perch treatment provided housing either with or without perches. The three stocking densities were 12 (low stocking density, LSD), 16 (medium stocking density, MSD), or 20 (high stocking density, HSD) birds/m2 and corresponded to 48, 64, and 80 birds per pen beginning at 1 day of age. The perches consisted of a wooden perch and a PVC perch (which included a horizontal section and a sloped (13°) section). In pens with perches, the perch design provided 580 cm of linear perching space per pen. The results showed that the LSD chickens had a higher (4.0%, P < 0.05) feed intake than the MSD and HSD chickens. Perch use by broilers was low but increased with age and peaked at 5 weeks of age (7.4%). Stocking density affected perch use, as the MSD chickens perched more frequently on both the PVC (2.4%, P = 0.01) and wood perches (3.7%, P < 0.05) than the LSD (PVC perch, 1.8%; wood perch, 3.3%) and HSD groups (PVC perch, 1.9%; wood perch, 2.5%). Perch availability affected behavioural patterns by increasing eating (P < 0.05) and sitting (P < 0.001) and decreasing walking (P < 0.001). Perch availability tended to prevent the development of footpad burn (P = 0.053) but had no detectable effect (P > 0.05) on the gait score or the development of hock burn. These results suggest that perches have a limited effect on the performance, behaviour, and welfare of broilers stocked at high densities. However, the effect of the interaction of perch × age on feed intake (P < 0.05), bodyweight gain (P < 0.05), and behaviour (eating and walking), the effect of the interaction of density × age on wood perch use (P < 0.05), and the effect of the interaction of perch × density × age on sitting behaviour (P < 0.01) indicated that perches have different effects on broilers of different ages stocked at different densities.

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