Effects of chronic heat exposure on gene expression in abdominal fat of growing broiler chickens.

Exposure to chronic heat stress not only reduces body weight gain in growing broilers, but also enhances fat deposition in the abdomen, subcutaneous, and intramuscular. To elucidate this phenomenon, numerous studies have examined changes in the transcripts, protein, and metabolic levels in the liver, the primary site of de novo fat synthesis in birds. On the other hand, changes in adipose tissue, the direct site of fat deposition, have not been unclear. To elucidate the changes in adipose tissue of chickens heat-exposure, we demonstrated the experiments rearing chickens in a heat environment (32°C) for 14 days, and then compared with the control group that reared in thermoneutral condition (22°C), and a pair-fed groups that reared in thermoneutral condition but feed intake was limited to the same levels as that in the heat-exposed group. Despite the feed intake was equal to that of the pair-fed group, the ratio of abdominal fat to body weight in the heat-exposed group was maintained at the same level as that in the control group. In addition, the heat-exposed group showed a significant decrease in the concentration of free fatty acids in plasma compared with the other 2 groups. Transcriptome analysis of abdominal fat between the heat-exposed and control groups revealed 459 differentially expressed genes were indicated. Notably, in heat-exposed group, the expression of genes related to lipid synthesis increased in adipose tissue compared with control group. Taken together, these results indicate that chronic heat has a lipid-deposition-promoting effect on growing broiler chicken adipose tissue Male broiler chicks were allocated to two treatments with 12 chickens at 21 days of age. Control and heat-stressed group chickens were exposed to thermoneutral condition (22.0 °C ± 0.5, humidity 50% ± 0.5) or heat stress condition (32.0 °C ± 0.5, humidity 50% ± 0.5) until 35 days of age. *************************************************************** Submitter states that missing raw files are due to file loss. ***************************************************************