This experiment was conducted to investigate the effects of constant moderate temperature on brain gut peptide contents in serum and hypothalamus,cecal volatile fatty acid contents and microflora diversity of broilers.One hundred and twenty 22-day-old Arbor Acres (AA) broilers were randomly divided into two groups and each group (chamber) contained six replicates with ten broilers (five males and five females) per replicate.The broilers in the 2 groups were allotted into environment chambers which kept at 21 ℃ and 60％ relative humidity for 7 days.When broilers were 29 days of age,the temperature of environment chamber for the experimental group was at 31 ℃ and the temperature of environment chamber for the control group was 21 ℃.The relative humidity of environment chambers for 2 groups remained constant at 60％,and the trial lasted for 14 days.The results showed as follows:1) at the day 7 of experiment,the contents of serum 5-hydroxytryptamine (5-HT) and vasoactive peptide (VIP) of broilers in 31 ℃ group were significantly lower than those in 21 ℃ group (P＜0.05),but no significant difference was found in serum substance P (SP) between the two groups (P＞0.05);at the day 14 of experiment,the contents of serum 5-HT,VIP and SP of the two groups were not significantly different (P＞0.05).2) At the day 7 of experiment,the contents of hypothalamus 5-HT,VIP and SP in the two groups were not significantly different (P＞0.05);at the day 14 of experiment,the content of hypothalamus 5-HT of broilers in 31 ℃ group was significantly lower than that in 21 ℃ group (P＜0.05),but no significant differences were found in the contents of hypothalamus VIP and SP between the two groups (P＞0.05).3) At the day 14 of experiment,the content of caecal isobutyric acid in 31 ℃ group was significantly higher than that in 21 ℃ group (P＜0.05);at the day 7 and 14 of experiment,the constant moderate temperature had no significant influences on the contents of caecal acetic acid,propionic acid,butyric acid,pentanoic acid and isopentanoic acid of broilers (P＞0.05).4) At the day 7 and 14 of experiment,the bands number and diversity indexes of caecal bacteria of broilers in 31 ℃ group were lower than those in 21 ℃ group.5) The constant moderate temperature was not conducive to the colonization of Clostridium termitidis and Bacteroides vulgatus.In conclusion,the constant moderate temperature can significantly reduce the contents of serum 5-HT and VIP at the day 7 of experiment,significantly rise the content of caecal isobutyric acid at the day 14 of experiment,and also can decrease the diversity of caecal bacteria,change the microflora structure and inhibit the growth of Clostridium termitidis and Bacteroides vulgatus.%本试验旨在研究持续偏热环境对肉鸡血清和下丘脑脑肠肽含量、盲肠挥发性脂肪酸含量和菌群多样性的影响.试验采用单因素设计,选取22日龄健康、体重相近的爱拔益加(AA)肉鸡120只,随机分成2个组,每组6个重复,每个重复10只(公母各占1/2).将6组肉鸡转入环境温度为21℃、相对湿度为60％的环境控制舱适应7d.29日龄时开始正式试验,试验组环境温度为31℃,对照组环境温度为21℃,相对湿度均为60％,试验条件维持至试验结束,共计14 d.结果表明:1)试验第7天,31℃组肉鸡血清5-羟色胺(5-HT)和血管活性肽(VIP)含量显著低于21℃组(P＜0.05),而血清P物质(SP)含量与21℃组无显著差异(P＞0.05);试验第14天,2组血清5-HT、VIP和SP含量均无显著差异(P＞0.05).2)试验第7天,2组肉鸡下丘脑5-HT、VIP和SP含量均无显著差异(P＞0.05);试验第14天,31℃组肉鸡下丘脑5-HT含量显著低于21℃组(P＜0.05),而下丘脑VIP和SP含量与21℃组无显著差异(P＞0.05).3)试验第14天,31℃组肉鸡盲肠异丁酸含量显著高于21℃组(P＜0.05);试验第7和14天,持续偏热环境对肉鸡盲肠乙酸、丙酸、丁酸、戊酸、异戊酸的含量均无显著影响(P＞0.05).4)试验第7天和14天,31℃组肉鸡盲肠细菌条带数以及多样性指数均低于21℃组.5)持续偏热环境不利于肉鸡盲肠中Clostridium termitidis和Bacteroides vulgatus的定植.由此可见,持续偏热环境使得肉鸡血清5-HT和VIP含量在试验第7天显著下降,盲肠异丁酸含量在试验第14天显著升高,同时还降低了肉鸡盲肠菌群的多样性,改变了菌群结构,抑制了Clostridium termitidis和普通拟杆菌(Bacteroides vulgatus)的生长.
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