Effects of Added Dietary Fiber and Rearing System on the Gut Microbial Diversity and Gut Health of Chickens

SIMPLE SUMMARY: In recent years, more and more research has focused on the effects of free-range rearing on the welfare of chickens. However, few works have focused on the gut microbial diversity and gut health of free-range chickens, especially when plant fibers are lacking in the wild. A lack of dietary fiber decreases the gut microbial diversity and even damages the gut health of a host, so we added eubiotic lignocellulose to the feed of caged and free-range Chinese local Bian chickens at three different levels (0%, 2%, and 4%) from September to November, aiming to observe the effects of added dietary fiber and the rearing system on the gut microbial diversity, microbial metabolism, and gut health of chickens, as well as to determine an appropriate amount of lignocellulose to effectively improve the gut microbial diversity and gut health of chickens when available plant fibers are scarce. The results showed that adding 2% lignocellulose was appropriate for free-range chickens, while 4% lignocellulose was appropriate for caged chickens. In addition, compared with the 2% lignocellulose in the cage system, 2% lignocellulose in free-range rearing could effectively improve unique microbial diversity and gut development. Adding an appropriate amount of dietary fiber may be good for the gut microbial diversity and gut health of caged chickens and free-range chickens who suffer from a lack of plant fibers in the wild. ABSTRACT: It is of merit to study the appropriate amount of dietary fiber to add to free-range chickens’ feed to improve their microbial diversity and gut health in times of plant fiber deprivation. Lignocellulose is a useful source of dietary fiber, and its positive effects on the growth performance and laying performance of chickens has already been proven. However, few researchers have researched the effects of adding it on the gut microbiota of chickens. In this research, we added three different levels of eubiotic lignocellulose (0%, 2%, and 4%) to the feed of caged and free-range Bian chickens from September to November, aiming to observe the effects of added dietary fiber and different rearing systems on the gut microbial diversity and gut health of chickens, as well as to determine an appropriate amount of lignocellulose. The results showed that adding dietary fiber increased the thickness of the cecum mucus layer and the abundance of Akkermansia and Faecalibacterium in caged chickens, and 4% lignocellulose was appropriate. In addition, adding lignocellulose increased the microbial diversity and the abundance of the butyrate-producing bacteria Faecalibacterium and Roseburia in fee-range chickens. The α-diversity and the length of the small intestine with 2% lignocellulose in free-range chickens were better than with 2% lignocellulose in caged chickens. Maybe it is necessary to add dietary fiber to the feed of free-range chickens when plant fibers are lacking, and 2% lignocellulose was found to be appropriate in this experiment. In addition, compared with caged chickens, the free-range chickens had a longer small intestine and a lower glucagon like peptide-1 (GLP-1) level. The significant difference of GLP-1 levels was mainly driven by energy rather than short chain fatty acids (SCFAs). There was no interaction between added dietary fiber and the rearing system on SCFAs, cecum inner mucus layer, and GLP-1.