To investigate the alleviative effects and molecular mechanisms of taurine supplementation on growth performance and carcass characteristics in broilers exposed to chronic heat stress, 144 male Arbor Acres broilers (28 d old) were randomly distributed to positive control (PC, 22°C, basal diet), heat stress (HS, consistent 32°C, basal diet), or heat stress + taurine (HS + T, consistent 32°C, basal diet + 5.00 g/kg taurine) groups, with 6 cages per group and 8 birds per cage. Chronic heat stress significantly decreased body weight, average daily gain, and average daily feed intake, and increased cloacal temperature and feed conversion ratio (FCR, P < 0.05). Though taurine supplementation tended to decrease the FCR in the HS + T group compared with the HS group after 14 d of heat exposure (P = 0.071), there were no significant alleviative effects of taurine supplementation on the increased cloacal temperature and decreased growth performance in chronic heat-stressed broilers (P > 0.05). After 7 and 14 d of heat exposure, taurine supplementation significantly increased the proportion of breast muscle and hormone-sensitive lipase activity in the abdominal fat (P < 0.05), and decreased the mRNA expressions of muscle atrophy F-box protein (MAFbx) and muscle ring-finger protein-1 (MuRF1) in breast muscle compared with the HS group (P < 0.05). After 7 d of heat exposure, taurine supplementation significantly increased serum non-esterified fatty acid concentration (P < 0.05), and decreased the mRNA expressions of acetyl-CoA carboxylase 1c (ACC) and muscular isoform of carnitine palmitoyl transferase 1 (M-CPT1) compared with the HS group (P < 0.05). In addition, the mRNA expressions of M-CPT1 and ribosomal protein S6 kinase, 70 kDa (p70S6K) in the HS + T group were significantly higher than those of the other two groups after 14 d of heat exposure (P < 0.05). In conclusion, taurine supplementation can improve carcass characteristics of chronic heat-stressed broilers by facilitating lipolysis for energy, enhancing protein synthesis, and suppressing protein degradation of the breast muscles.
Keywords: broiler; carcass characteristics; chronic heat stress; growth performance; taurine.
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