关键词: 热应激, 肉鸡, 回肠, 微生物菌群, 采食量

Abstract:

【Objective】 To explore how heat stress influences the composition and structure of intestinal microbiota in broilers, and to provide a basis for alleviating the adverse effects of heat stress. 【Method】 144 broilers ((1 771±40) g, 35 d) were randomly divided into three groups with six replicates and raised in three controlled climate chambers from 35 to 42 days in this study. They were allocated to one of a thermoneutral control group (TC, 21℃, ad libitum), a heat stress group (HT, 31℃, ad libitum), or a pair-feeding group（PF, 21℃, pair-feeding as much as the consumption of the HT birds）. 【Result】 Compared with broilers in TC, the feed intake and body weight gain were significantly decreased and F/G was increased in broilers of HT (P<0.01), the feed intake and body weight gain were also significantly decreased in broilers of PF (P<0.01). The feed intake of broilers in HT was as same as it in PF, but the body weight gain in HT was lower than it in PF, and the F/G was higher (P<0.05), which indicated that the heat stress still decreased the body weight gain of broilers even at the same level of feed intake. Compared with broilers in TC, the core temperature (P=0.079) and serum corticosterone content (P=0.071) have an increasing tendency in broilers of HT, and have similar levels in PF (P>0.05). The richness of species（sobs and Chao1）and diversity indices（Shannon）of samples in the HT and PF group were higher than those in the TC group (P<0.05). There was no significant difference in terms of the diversity estimators of the ileal microbiota between the HT and the PF groups. The PCoA showed that the HT and PF groups were gathered together but were distinctly separated from the TC group. This tendency was also verified by the similarity analysis. Moreover, the feed consumption was significantly correlated with the principal coordinate 1 in the PCoA (R = 0.786, P<0.001), but the body temperature or the serum corticosterone was not correlated with the principal coordinate 1 (P>0.05). Furthermore, 18 differential genera between the HTG and the TC groups were identified by LEfSe analysis (score ≥ 3). The relative abundance of these genera in the PF and HT groups was similar but had significant differences compared with that in the TC group. In addition, among the 50 most abundant genera in the ileal microbiota, the feed consumption was significantly correlated with 30 genera, but the body temperature and serum corticosterone were significantly correlated with only two and no genera, respectively. 【Conclusion】 The core temperature and serum corticosterone content were different, the feed intake was similar between HT and PF, and the composition and community structure of ileal microbiota were similar between those two groups; the core temperature and serum corticosterone content were similar, but the feed intake was different between TC and PF, and the composition and community structure of ileal microbiota were also different between those two groups, these results indicate that the effects of constant heat stress on composition and community structure of ileal microbiota in broilers are related to reduced feed consumption. This conclusion was also proved by the results of correlation analysis.

Key words: heat stress, broilers, ileum, microbiota, feed consumption