Effects Of Coprophagy On Growth Performance,Intestinal Microecology And Meat Quality Of New Zealand White Rabbits

Coprophagy is an instinct behavior of rabbits.Over the long-term natural selection and evolution,rabbits have developed and maintained the behavior and habit of ingesting soft feces to adapt to adverse living environments.Due to the digestion characteristics and limited food supply,many small herbivores including rabbits have expanded the size of their foregut or hindgut regions to facilitate the fermentation of indigestible dietary fibers and engaged in coprophagy to meet their nutrition requirement.Studies showed that the practice of soft feces ingestion provides a strategy for rabbits to reabsorb the nutrients that are excreted with the feces and replenishes the microorganisms to cecum to maintain the homeostasis of gut microbiota communities.In recent years,rabbit meat is becoming increasingly popular for its delectable taste and specific nutritional properties,such as high contents of PUFAs,proteins,EAAs,and relatively low fat and cholesterol contents,thus enabling rabbit to be an ideal source of animal protein supplier.Studies have shown that coprophagy is physiologically important for the maintenance of the intestinal microbiota and nutrient uptake in rabbits,but systematic studies on the effects of coprophagy on growth performance and meat quality in rabbits are lacking.In this study,fasting caecotrophy model was established to explore the effects of fasting cecotrophy on growth performance,intestinal microecology and meat quality of rabbits.The main results were as follows:(1)Coprophagy prevention had a significant effect on the growth performance of New Zealand white rabbits.Compared with the control group(CON)and the shamcoprophagy prevention group(SCP),the final body weight(P < 0.05)and average daily gain(P < 0.05)of rabbits in the coprophagy prevention group(CP)decreased significantly,and the feed conversion ratio(P < 0.05)increased significantly.(2)Coprophagy prevention had a significant effect on the meat quality of New Zealand white rabbits.Compared with CON group and SCP group,the a* at 45 min and 24 h after slaughter(P < 0.05)and drip loss(P < 0.05)increased significantly,and coarse ash content(P < 0.05)decreased significantly of hind leg muscle of CP group.In addition,the total area of lipid droplet accumulation(P < 0.001)and triglyceride content(P < 0.05)of CP group increased significantly.Coprophagy prevention changed the fatty acid composition and content of hind leg muscle tissue of New Zealand white rabbits.Compared with CON group and SCP group,the content of palmitic acid(C16:0)in hind leg muscle of CP group increased significantly(P < 0.05),the content of total saturated fatty acids increased significantly(P < 0.05),and the content of total unsaturated fatty acids decreased significantly(P < 0.05).Coprophagy prevention also changed the amino acid composition and content of hind leg muscle tissue of New Zealand rabbits.In CP group,the content of essential amino acids decreased significantly(P < 0.05),while the content of non-essential amino acids increased significantly(P < 0.05).(3)HE staining of cecal tissue showed that compared with CON group and SCP group,cecal villi structure was destroyed and intestinal glands increased in CP group.Fasting cecotrophy led to cecal inflammation in rabbits.The p H value of cecal contents in CP group was significantly higher than that in CON group and SCP group(P < 0.01).Compared with CON group and SCP group,the contents of formic acid(P < 0.05),isovaleric acid(P < 0.05)and valeric acid(P < 0.05)in cecal contents in CP group were significantly higher than those in CP group.In addition,the contents of isobutyric acid(P < 0.05)and butyric acid(P < 0.05)in CP group were significantly lower than those in CON group and SCP group.The results of 16 S r DNA sequencing of cecal contents showed that the abundance of Oscillospira in CP group was significantly lower(P <0.01)than that in CON group,and that of Ruminococcus in CON group was significantly lower(P < 0.05)than that in CON group and SCP group.Oscillospira,Jeotgalicoccus,Staphylococcus,Campylobacter and Butyricimonas were the main biomarker of CON group,Pseudomonas and Sutterella were the main biomarker of SCP group,and Enterobacter,Acinetobacter,AF12,Shigella,Butyricicoccus,Parabacteroides,Oxalobacter and Desulfovibrio were the main biomarker of CP group.(4)The protein library of hind leg muscle tissue of fasting caecotrophy model in New Zealand white rabbits was successfully constructed.A total of 267 differentially DEPs were detected in the hind leg muscles of CP group and CON group,of which 159 proteins were up-regulated in CP group and 108 proteins were down-regulated in CP group,while 196 DEPs were detected in CP group and SCP group,of which 118 proteins were up-regulated in CP group and 78 proteins were down-regulated in CP group.The DEPs in the hind leg muscle of CP group and CON group was enriched by GO.The main items of molecular function were protein binding(such as actin filament binding,tubulin binding,potassium ion binding,oxygen binding)and phosphatase activity.The cell component mainly enriched myofibril(including Z disc,basement membrane,and myosin complex).The main item of biological process is transport process(including mitochondrial electron transport,Cyt C to oxygen,protein import into nucleus,and muscle tissue morphogenesis).KEGG enrichment analysis of DEPs of CP group and CON group showed that the main enrichment pathways included oxidative phosphorylation,non-alcoholic fatty liver disease,Parkinson’s disease,muscle contraction,carbon metabolism,and pyruvate metabolism signaling pathways.And the functions and pathways of the DEPs of CP vs CON and CP vs SCP were similar.Elisa and Westernblot verification tests showed that the inhibition of mitochondrial oxidative phosphorylation and ATP production in CP group may be the potential regulatory mechanism leading to abnormal lipid accumulation in skeletal muscle.In this study,after obtaining the phenotypic and meat quality data of fasting caecotrophy model in rabbits,the typical differential microorganisms,differentially expressed proteins and regulatory pathways in CP group were screened by 16 S r DNA and proteomics sequencing,and verified by molecular biology methods.In this study,it was found that the inhibition of mitochondrial oxidative phosphorylation and ATP production was the potential mechanism of fasting caecotrophy on lipid accumulation and fatty acid composition in rabbit skeletal muscle.