关键词: 肉鸡, 偏热环境, 脑肠肽, 肠道菌群

Abstract:

【Objective】Stress can alter the function of brain - gut axis and the structure of intestinal flora, among which heat stress is one of the most important environmental factors affecting the health of livestock and poultry. This study was carried out to investigate the effects of the daily cycle variation of the moderate ambient temperatures on the serum brain gut peptide and the diversity of caecal microflora in broilers, and to provide a theoretical basis for the healthy broiler breeding mode. 【Method】 The study included trials with Arbor Acres (AA) broilers. At the 22d, 120broilers with equal average body weights were selected, randomly divided into 2treatments × 6 replicates of 10 birds each(male and female half and half) . The pretest period lasted for 7 days and broilers were kept at 21℃ and 60% relative humidity. When the chickens were aged 29 days, formal tests began. The environmental temperature was changed by 24h cycle (26 -29, -32, -26, -29), and the relative humidity was set to 35%, 60%, 85%, respectively. Both kept constant until the end of the experiment. The trial period lasted for 14 days. On day 21 and 42, one birds from each replicate were randomly selected and killed. The broiler was sampled with jugular vein. The contents of 5-HT, VIP and CCK in serum of broilers were measured with Elisa kit. Meanwhile cecal contents were aseptically collected, placed in a centrifugal tube, rapidly frozen in liquid nitrogen, and stored at -80℃. The effect of different humidity on serum brain gut peptide and bacterial diversity in the ceacal digesta of broilers at the daily cycle variation of the moderate ambient temperatures was studied by using 16S r DNA-based denaturing gradient gel electrophoresis (DGGE). 【Result】(1) At the 7d , the content of Serum 5-HT at the daily cycle variation of the moderate ambient temperatures was higher than control group (P<0.05); the content of serum 5-HT and VIP in the control group and were no significant difference; at the 14d, the content of serum VIP in broilers at the daily cycle variation of the moderate ambient temperatures was lower than the control group (P<0.05); the content of serum 5-HT and SP in the control group and were no significant difference. (2)At the 7d, the bacteria bands at the daily cycle variation of the moderate ambient temperatures were lower than the control group; at the 14d, the bacteria bands at the daily cycle variation of the moderate ambient temperatures and the control group were same, but broiler cecal microflora diversity decreased at the daily cycle variation of the moderate ambient temperatures. (3) Common microflora of broiler cecum included Clostridium josui, Bacteroides vulgatus, Parabacteroides johnsonii, Bacteroides dorei and Ruminococcus flavefaciens; The daily cycle variation of the moderate ambient temperatures was beneficial to the growth of Parabacteroides johnsonii and Bacteroides dorei, and inhibited the colonization of Intestinimonas butyriciproducen and Subdoligranulum variabile.【Conclusion】Compared with the control group, at the 7d, the content of serum 5-HT in broilers increased at the daily cycle variation of the moderate ambient temperatures , and at the 7d, the serum VIP content in broilers decreased at the daily cycle variation of the moderate ambient temperatures , and there was no significant difference in SP between the two groups; The daily cycle variation of the moderate ambient temperatures affected the cecal microflora structure and diversity in broilers.

Key words: broiler, moderate temperatures, serum brain gut peptide, caecal microflora