Molecular mechanism underlying the effect of illumination time on the growth performance of broilers via changes in the intestinal bacterial community

The circadian rhythms associated with light have important effects on the growth, metabolism, immunity and reproduction of broilers. However, there is a lack of systematic evaluations of the effect of the light cycle on intestinal microbes and the nutritional metabolism of these microbes in broilers. This study was designed to study the effects of the light cycle on the intestinal bacterial community structure and growth of broilers. In this study, Arbor Acre (AA) broilers were fed under a short photoperiod (1L:23D), a long photoperiod (23L:1D), and a normal photoperiod (16L:8D), respectively. The feed conversion ratio of the broilers was calculated, and the levels of endocrine hormones, such as melatonin, insulin and glucagon, were determined. Intestinal contents were collected from the small intestines of the broilers after slaughtering, and the V3+V4 region of the 16s rDNA gene was sequenced. The results demonstrated that changes in the light cycle could affect the synthetic rhythms of melatonin, insulin and glucagon. Compared to short and normal photoperiod, long photoperiod significantly increased the abundances of Barnesiella species in intestinal microbes and decreased the abundances of Bacteroides and Alistipes species. Cluster of Orthologous Groups of proteins analysis indicated that prolongation of the illumination increased the abundances of bacterial genes with glycometabolic and membrane transport functions in intestinal microorganisms. A model was established in this study, and our results showed that prolonged illumination altered the intestinal microbial community structures of broilers, increased the absorption and utilization of polysaccharides in broilers, and reduced the feed-to-meat ratios. To the best of our knowledge, this is also the first study to describe the molecular mechanism underlying the effects of the light cycle on the uptake and utilization of nutrients that occur via modification of the intestinal microbial community structure in broilers.