Possible role of corticosterone on behavioral, physiological, and immune responses in chicks.

Glucocorticoids are one of steroid hormone and have a variety of functions including stress response, carbohydrate metabolism, and modulation of immune system in vertebrates. Corticosterone is the main glucocorticoid in birds, although the precise role of the glucocorticoid during immune challenge is not fully understood. Therefore, the purpose of the present study was to determine if a single subcutaneous injection of corticosterone could affect inflammation-related gene expressions in the spleen and liver of chicks (Gallus gallus). In addition, the effects of corticosterone injection on the food intake, cloacal temperature, formation of conditioned visual aversion, and plasma constituents were also measured. Corticosterone did not affect the food intake or cloacal temperature and did not cause conditioned visual aversion in chicks. The corticosterone injection was associated with a significant decrease in gene expression of several pro-inflammatory cytokines including inducible nitric oxide synthase and cyclooxygenase-2 in the spleen and liver at 1 and 3 h post-injection. Corticosterone increased the plasma glucose and uric acid concentrations and the antioxidant capacity. In summary, the present study suggests that corticosterone is likely not associated with food intake, cloacal temperature or the development of aversive sensation, but suppresses the synthesis of inflammation-associated bioactive molecules and increases the antioxidant capacity in chicks.

Effects of high ambient temperature on plasma metabolomic profiles in chicks.

Exposure to high ambient temperature is detrimental to the poultry industry. To understand the influence from a metabolic perspective, we investigated the effects of exposure to high ambient temperature on plasma low-molecular-weight metabolite levels in chicks using gas chromatography/mass spectrometry-based non-targeted metabolomic analysis. Heat exposure for 4 days suppressed growth and food intake. Of the 92 metabolites identified, the levels of 29 decreased, whereas the levels of nine increased. We performed an enrichment analysis on the identified metabolites and found 35 candidates for metabolic processes affected by heat exposure. Among them, the sulfur amino acid metabolic pathway was clearly detected and the levels of the following related metabolites were decreased: cystathionine, cysteine, cystine, homocysteine and hypotaurine. Changes in the kynurenine pathway in tryptophan metabolism, which is linked to the immune system and oxidative stress, were also observed: kynurenine and quinolinic acid levels increased, whereas nicotinamide levels decreased. These results suggest the possible involvement of various metabolic processes in heat-exposed chicks. Some of these metabolites would be important to understand the mechanism of biological responses to high ambient temperature in chicks.