Li Xiumei, Zhang Minhong, Feng Jinghai, Zhou Ying
State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Animals (Basel). 2021 May 20;11(5):1467. doi: 10.3390/ani11051467.
Heat stress has an adverse effect on the development of poultry farming, which has always aroused great concern. This study was carried out to investigate the protein breakdown mechanism responsible for the suppressive effect of constant heat stress on muscle growth in growing broilers. A total of 96, 29-day-old, Arbor Acres male broilers were randomly divided into two groups, a thermoneutral control (21 ± 1 °C, TC) and a heat stress (31 ± 1 °C, HS) group, with six replicates in each group and eight birds in each replicate. The trial period lasted for 14 d, and the trial was performed at 60 ± 7% relative humidity, a wind speed of <0.5 m/s and an ammonia level of <5 ppm. The results showed that the average daily feed intake and average daily gain in the HS group were distinctly lower than those in the TC group ( < 0.05), whereas the HS group showed a significantly increased feed conversion ratio, nitrogen excretion per weight gain and nitrogen excretion per feed intake compared to the TC group ( < 0.05). In addition, the HS group showed a significantly reduced breast muscle yield and nitrogen utilization in the broilers ( < 0.05). The HS group showed an increase in the serum corticosterone level ( < 0.05) and a decrease in the thyroxine levels in the broiler chickens ( < 0.05) compared to the TC group, whereas the HS group showed no significant changes in the serum 3,5,3'-triiodothyronine levels compared to the TC group ( > 0.05). Moreover, the HS group showed increased mRNA expression levels of myostatin, Smad3, forkhead box O 4, muscle atrophy F-box and muscle ring-finger 1, but reduced mRNA expression levels of the mammalian target of rapamycin, the protein kinase B and the myogenic determination factor 1 ( < 0.05). In conclusion, the poor growth performance of birds under constant heat stress may be due to an increased protein breakdown via an mRNA expression of myostatin and related factors.
热应激对家禽养殖的发展具有不利影响，这一直引起人们的高度关注。本研究旨在探究持续热应激对生长肉鸡肌肉生长产生抑制作用的蛋白质分解机制。选取96只29日龄的艾拔益加雄性肉鸡，随机分为两组，一组为热中性对照组（21±1℃，TC），另一组为热应激组（31±1℃，HS），每组6个重复，每个重复8只鸡。试验期持续14天，试验在相对湿度60±7%、风速<0.5 m/s、氨水平<5 ppm的条件下进行。结果表明，HS组的平均日采食量和平均日增重明显低于TC组（P<0.05），而HS组的饲料转化率、每增重氮排泄量和每采食量氮排泄量均显著高于TC组（P<0.05）。此外，HS组肉鸡的胸肌产量和氮利用率显著降低（P<0.05）。与TC组相比，HS组肉鸡血清皮质酮水平升高（P<0.05），甲状腺素水平降低（P<0.05），而HS组血清三碘甲状腺原氨酸水平与TC组相比无显著变化（P>0.05）。此外，HS组肌肉生长抑制素、Smad3、叉头框O 4、肌肉萎缩F盒蛋白和肌肉环形指蛋白1的mRNA表达水平升高，但雷帕霉素靶蛋白、蛋白激酶B和成肌决定因子1的mRNA表达水平降低（P<0.05）。总之，持续热应激条件下家禽生长性能不佳可能是由于肌肉生长抑制素及相关因子的mRNA表达导致蛋白质分解增加所致。
