Abstract
The aim of this study was to evaluate the effects of high ambient temperature (HT) and orotic acid supplementation on the plasma and muscle metabolomic profiles in broiler chickens. Thirty-two 14-day-old broiler chickens were divided into four treatment groups that were fed diets with or without 0.7% orotic acid under thermoneutral (25 ± 1 °C) or cyclic HT (35 ± 1 °C for 8 h/day) conditions for 2 weeks. The chickens exposed to HT had higher plasma malondialdehyde concentrations, suggesting an increase in lipid peroxidation, which is alleviated by orotic acid supplementation. The HT environment also affected the serine, glutamine, and tyrosine plasma concentrations, while orotic acid supplementation affected the aspartic acid, glutamic acid, and tyrosine plasma concentrations. Untargeted gas chromatography–triple quadrupole mass spectrometry (GC-MS/MS)-based metabolomics analysis identified that the HT affected the plasma levels of metabolites involved in purine metabolism, ammonia recycling, pyrimidine metabolism, homocysteine degradation, glutamate metabolism, urea cycle, β-alanine metabolism, glycine and serine metabolism, and aspartate metabolism, while orotic acid supplementation affected metabolites involved in pyrimidine metabolism, β-alanine metabolism, the malate–aspartate shuttle, and aspartate metabolism. Our results suggest that cyclic HT affects various metabolic processes in broiler chickens, and that orotic acid supplementation ameliorates HT-induced increases in lipid peroxidation.
Highlights
Ambient temperatures above the thermoneutral zone cause environmental heat stress
The final body weight, body weight gain, and feed conversion ratio were not affected by either the high ambient temperature (HT) or orotic acid supplementation, whereas the feed intake was significantly depressed in the chickens kept under the HT conditions (Table 1)
The body temperatures of the chickens kept in the HT environment were significantly increased compared with those of the chickens kept under thermoneutral conditions
Summary
Chickens are more vulnerable to heat stress than other domestic animals, because they lack sweat glands and have higher body temperatures [1,2] Under such high ambient temperature (HT) conditions, the generation of reactive oxygen species increases in various body tissues as the heat load increases [3]. Gas chromatography–mass spectrometry (GC-MS)-based, untargeted metabolomics analysis has been used to comprehensively characterize the effects of HT on the physiology of chickens [15], and has found that the plasma levels of 38 metabolites changed significantly when chickens were exposed to chronic heat (38 ◦ C) for 4 days These altered metabolites indicated that such heat exposure affected
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