Effects Of Caecotrophy On The Gut Microbiome And Growth Of Rex Rabbit

Small and medium-sized herbivorous animals have higher metabolic rate and smaller volume of gastrointestinal tract.Mean residence time of food in the digestive tract is shorter.However,the time of fermentation is much longer than mean residence time of food.In the long process of adaptive evolution,small and medium-sized herbivorous animal has evolved a variety of mechanisms to improve the effective rate of digestion on aspects of physiologyical behaviors,such as colonic separation and coprophagy.Caecotrophy is an special type of coprophagy.The nutritional effect of caecotrophy on small and medium-sized herbivores have been widely studied.However,soft feces not only have difference in nutrient content with hard feces,but also in bacteria content.The effect of caecotrophy on gut microbiome and whether caecotrophy promotes growth by regulation of intestinal flora are still unknown.In order to explore these scientific questions,we choose Rex Rabbit,one species of lagomorphs,who are the best representative animals for caecotrophy,as a model animal.Firstly,we studied the differences on microbiota composition between soft feces and hard feces and between groups,who has different weight.We sequenced the V4 hypervariable region of 16S rRNA gene using Illumina MeSiq platform.we further studied the effects of caecotrophy on gut microbiome and growth of Rex Rabbit using the self-designed circles of preventing caecotrophy and allowing caecotrophy.we chose 111 healthy Rex Rabbits weaned at 40d and randomly assigned them to three groups:caecotrophy-prevented group(CP,n=39),caecotrophy-allowed group(CA,n=38)and control group(CON,n=34).We weighted the rabbits at day 40,49,56,63,70,84 and 98,respectively.And we sampled the feces of Rex Rabbits for high-throughput sequencing.Our results showed that:(1)The microbiota composition were different between soft feces and hard feces.Soft feces had more relative abundance of Ruminococcaceae,Clostridiales and Adlercreutzia.(2)The microbiota composition were also different between Rex Rabbits with different weights.Rex Rabbits who had higher weight had more Lactococcus and Lactobacillus in hard feces and more of RF32,Alphaproteobacteria in soft feces than low weight Rex Rabbit.(3)The weights of caecotrophy-allowed group were significantly higher than caecotrophy-prevented group.(4)Preventing caecotrophy changed the microbiota composition of Rex Rabbits:the relative abundance of Blautia and Eubacterium had increased and RF39,Barnesiellaceae decreased.(5)Caecotrophy had different effects to females and males,with more severe effect on females.Caecotrophy had more effects on the relative abundance of Clostridiales,Bacteroidesand RF39,Blautia in females and males Rex Rabbits,respectively.(6)RF39,Clostridiales and Ruminococcaceae.which were enriched in caecotrophy-allowed group,had a positive relationship with the growth of Rex Rabbit.(7)PICRUSt predicted that female Rex Rabbits of caecotrophy-allowed group increased the abundance of nutrients metabolism pathway,immune system pathway and digestive system pathway.And males of caecotrophy-allowed group increased the abundance of circulatory system pathway.Meanwhile,the females and males Rex Rabbits of caecotrophy-allowed group had more abundance of toxic and harmful substances degradation pathway than caecotrophy-prevented group.In general,our study illustrated that caecotrophy shapes the gut microbiome,and the growth and health of Rex Rabbits may be the results of shaping gut microbiome.