Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
Institute of Animal Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
Poult Sci. 2019 Aug 1;98(8):3268-3277. doi: 10.3382/ps/pez123.
Broiler chicks in the immediate posthatch handling period are exposed to thermal stress, with potentially harmful consequences for muscle growth and structure (e.g., less protein and more fat deposition). We addressed the effects of broiler chicks' exposure to various ambient temperatures during the first 13 D posthatch on their performance, as well as on muscle development and structure, up to day 35. Body weight and pectoralis muscle growth were lower throughout the entire period in the high-heat-exposed chicks (39°C, Hot) and to a lesser extent in the mild-heat-exposed chicks (35°C, Hot Mild) than in the Control chicks that were raised under a commercial protocol. In the cold-exposed chicks (29oC, Cold), BW and pectoralis muscle absolute growth were similar to the Control group throughout the entire period. The lower body and muscle growth in the Hot and Hot Mild groups were reflected in a lower number of myonuclei expressing proliferating cell nuclear cell in pectoralis major muscle cross sections sampled on day 8, in the distribution of myofibers as the experiment progressed, and in mean myofiber diameter on day 35, whereas in the Cold group, these numbers exceeded that of the Control group. However, TUNEL assay revealed similar cell survival in all groups. Hematoxylin-eosin and Oil red O staining revealed the highest fat deposition in the pectoralis muscle derived from the Hot group, whereas lower fat deposition was observed in the Control Cold group. These results were corroborated by immunostaining for CCAAT/enhancer binding protein β in the pectoralis muscle, the levels of which were significantly higher in the Hot and Hot Mild groups on day 35 than in the Control group. Similar results were observed with Sirius red staining for collagen content in the pectoralis muscle. Together, the results imply long-term effects of chronic heat stress vs. cold stress in the early posthatch period on the broiler's body and muscle growth in general and myodegeneration of the pectoralis muscle in particular.
肉仔鸡在孵化后的立即处理期间会受到热应激的影响，这可能对肌肉生长和结构产生有害影响（例如，蛋白质减少，脂肪沉积增加）。我们研究了肉仔鸡在孵化后第 13 天之前暴露于不同环境温度对其性能的影响，以及对肌肉发育和结构的影响，直到第 35 天。在整个试验期间，高温暴露组（39°C，高热）和轻度高温暴露组（35°C，低热）的雏鸡体重和胸肌生长均低于对照组，而低温暴露组（29°C，低温）的雏鸡体重和胸肌绝对生长与对照组相似。高热和低热组的体重和肌肉生长较低，这反映在第 8 天取样的胸大肌横切面上表达增殖细胞核抗原的肌细胞核数量较少，随着试验的进行肌纤维的分布以及第 35 天的平均肌纤维直径也较低，而在低温组，这些数量超过了对照组。然而，TUNEL 检测显示所有组的细胞存活率相似。苏木精-伊红和油红 O 染色显示，来自高热组的胸肌中脂肪沉积最高，而对照组和低温组的脂肪沉积较低。这些结果通过胸大肌中 CCAAT/增强子结合蛋白 β 的免疫染色得到证实，在第 35 天，高热和低热组的该蛋白水平明显高于对照组。胸大肌胶原蛋白含量的天狼星红染色也得到了类似的结果。综上所述，这些结果表明，在孵化后的早期阶段，慢性热应激与冷应激对肉鸡的身体和肌肉生长，特别是胸大肌的肌退化，会产生长期影响。
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