Circadian disruption and divergent microbiota acquisition under extended photoperiod regimens in chicken

The gut microbiota is crucial for metabolic homeostasis, immunity, growth and overall health, and it recognized that early-life microbiota acquisition is a pivotal event for later life health. Recent studies show that gut microbiota diversity and functional activity are synchronized with the host circadian rhythms in healthy individuals, and circadian disruption elicits dysbiosis in mammalian models. However, no studies have determined the associations between circadian disruption in early life, microbiota colonization, and the consequences for microbiota structure in birds. Chickens, as a major source of protein around the world, are one of the most important agricultural species, and their gut and metabolic health are significant concerns. The poultry industry routinely employs extended photoperiods (>18 hours’ light) as a management tool, and their impacts on the chicken circadian, its role in gut microbiota acquisition in early life, and consequences for later life microbiota structure remain unknown. In this study, the objectives were to a) characterize chicken circadian activity under two different light regimes (12/12 hours’ Light/Dark and 23/1 hours Light/Dark), b) characterize gut microbiota acquisition and composition in the first four weeks of life, c) determine if gut microbiota oscillate in synchrony with the host circadian, and d) to determine if fecal microbiota is representative of cecal microbiota. Expression of clock genes ( clock , bmal1 , and per2 ) were assayed, and fecal and cecal microbiota was characterized using 16s rRNA amplicon analyses from birds raised under two photoperiod treatments. Chickens raised under 12/12 LD photoperiods exhibited rhythmic clock gene activity, which was absent in birds raised under the extended (23/1 LD) photoperiod. This study is also the first to report differential microbiota acquisition under different photoperiod regimes. Gut microbiota members showed a similar oscillating pattern as the host, but this association was not as strong as found in mammals. Finally, the fecal microbiota was found to be not representative of cecal microbiota membership and structure. This is one of the first studies to demonstrate the use of photoperiods to modulate microbiota acquisition, and show its potential utility as a tool to promote the colonization of beneficial microorganisms.