The effects of chronic heat stress on the growth performance, digestive and absorbtive-related parameters, and jejunal metabolomics in broilers

Heat stress (HS) is one of the major influencing factors limiting the development of poultry farming. To investigate the effect of chronic HS on the intestinal digestion and absorption function, we divided 80 broilers to control group (TN group), chronic HS group (CHS group), and then illustrated the effects using growth performance, gas chromatography-mass spectrometry (GC-MS)-based metabolomics, digestive and absorptive capacity, and apparent digestibility. Broilers in the CHS group were exposed to 12 h/day HS (32 ± 1 ℃) for 14 consecutive days, and the rest of the time per day was maintained at 24 ± 1 ℃, which was the same as that used for the TN group. The jejunum samples were collected at the end of the experiment, and tested for relevant indexes, and the GC-MS technique was applied to obtain two groups of broiler jejunum metabolic profiles. The study showed that HS reduced the average daily feed intake (ADFI), average daily grit (ADG), intestinal digestive enzyme activity, D-xylose and GSH absorption levels, apparent digestibility, and elevated feed conversion ratio (FCR). A total of 370 metabolites in the broiler jejunum were identified, and 43 up-regulated and 22 down-regulated metabolites were screened. Enrichment analysis of metabolic pathways revealed that eight metabolic pathways were significantly altered (mainly related to energy metabolism). These results indicate that changes in cellular metabolism in the jejunum when broilers are subjected to HS, decreased the activity of digestive enzymes in the jejunum, resulting in a decrease in digestibility and consequently affecting growth performance.