Effects Of Different Diets On Rumen Development Of 20~60 Day-Old Goat Kids

The aim of this study was to investigate study the effects of different diets on the rumen development of 20~60 day-old goat kids.Seventy-two 20-d Haimen goat kids with similar body weight were randomly allocated into 3 groups with 6 replicates in each group and 4 goat kids in each replicate.The goat kids were fed with only milk replacer(MRO),milk replacer + concentrates(MRC),or milk replacer + concentrates and alfalfa pellets(MCA).The experiment lasted for 40 days after a 3-d adaptation period.To explore the effects of different diets on rumen fermentation,rumen microflora and rumen epithelial gene expression of 20~60 day-old goat kids,in order to provide a theoretical basis for early nutritional regulation of goat kids.This study is divided into four parts.Experiment 1: Effects of different diets on growth performance and apparent digestibility of 20~60 day-old goat kidsThis study was designed to investigate the effects of different diets on growth performance and apparent digestibility of 20~60 day-old goat kids.The experiment was designed with single factor and diet as test factor.The kids were breast-feeding from 0 to 20 days old.Seventy-two 20-d Haimen goat kids with similar body weight were randomly allocated into 3 groups with 6 replicates in each group and 4 goat kids in each replicate.The goat kids were fed with only milk replacer(MRO),milk replacer + concentrates(MRC),or milk replacer + concentrates and alfalfa pellets(MCA).At the age of 20 to 60 days,the kids are free to consume concentratess and alfalfa pellets,free to drink water.The results showed that the average daily weight gain in MRC and MCA was significantly higher than that in MRO(P<0.05).The apparent digestibility of dry matter,crude protein,crude fat,total energy and non-fibrous carbohydrates in MRO were significantly higher compared with MRC and MCA(P<0.05).The digestible dry matter intake and digestible protein intake of MCA were significantly higher compared with MRC(P<0.05),and MRC was significantly higher than MRO(P<0.05).Conclusion: Feeding concentrates or concentrates + alfalfa pellets at 20~60 days of age could significantly improve the growth performance of goat kids.However,feeding concentrates or concentrates + alfalfa pellets at 20~60 days of age in goat kids significantly reduced the apparent digestibility of nutrients.Experiment 2: Effects of different diets on rumen fermentation and tissue morphology of 20~60 days-old goat kidsThis study was designed to investigate the effects of different diets on rumen fermentation and tissue morphology of 20~60 days-old goat kids.Trial design was the same as experiment 1.At the age of 60 days of goat kids,one healthy goat kid,weighing close to the average body weight,was slaughtered for each treatment.The results showed that the rumen weight,the ratio of rumen to complex stomach and the proportion of rumen to the live weight in MCA were significantly higher than those in MRC(P<0.05).The pH and ammonia nitrogen content of rumen fluid in MRC and MCA were significantly lower compared with the MRO(P<0.05).The rumen microbial protein content in MRC and MCA was significantly higher than that in MRO(P<0.05).The total volatile fatty acid content,acetate and butyrate content of rumen fluid in MCA were the highest,which was significantly higher than that in MRC(P<0.05),and MRC was significantly higher than MRO(P<0.05).The length of rumen papilla in MCA and MRC was significantly higher than that in MRO(P<0.05).The width of rumen papilla in MCA was significantly higher compared with MRO(P<0.05).There was a significant negative correlation between rumen fluid pH and rumen papilla length and width(P<0.05).The contents of total volatile fatty acid content,microbial protein,acetate,propionate and butyrate in rumen fluid were significantly positively correlated with the length of rumen papilla(P<0.05).Experiment 3: Effects of different diets on rumen microflora of 20~60 day-old goat kidsThis study was designed to investigate the effects of different diets on rumen microflora of 20~60 day-old goat kids.Trial design was the same as experiment 1.At the age of 60 days of goat kids,one healthy goat kid,weighing close to the average body weight,was slaughtered for each treatment.Rumen contents and ventral sac epithelium were collected to determine microflora.The rumen microbial richness in MRC and MCA was significantly lower than that in MRO(P<0.05).The relative abundance of the rumen content Bacteroidetes in MCA was significantly lower compared with MRO(P<0.05).The relative abundance of the rumen contents Firmicutes in MRC and MCA was higher compared with MRO(P<0.05).The relative abundance of the rumen content Fibrobacteres in MCA was significantly higher than that in MRC(P<0.05),and MRC was higher than MRO(P<0.05).The relative abundance of the rumen contents Prevotella in MRC and MCA was significantly higher than that in MRO(P<0.05).The relative abundance of the Fibrobacter and Succiniclasticum in MCA was significantly higher compared with MRO and MRC(P<0.05).The relative abundance of Succinivibrio and Ruminococcus in MCA were higher than that in MRO(P<0.05).Through 16 S rDNA functional prediction,the results indicate that Ruminococcus unclassified is the main driving factor for the Transcription and Cellular_Processes_and_Signaling metabolic pathways common to MRC and MCA.The microbial composition of rumen contents and epithelium was significantly different.The microbial diversity of rumen epithelium in MRC and MCA was significantly higher than that in MRO(P<0.05).The relative abundance of Bacteroidetes in the rumen epithelium of the MRC and MCA was significantly higher than that of the MRO(P<0.05),and the relative abundance of the Firmicutes was significantly lower than that of the MRO(P<0.05).The relative abundance of Proteobacteria in the rumen epithelium of the MCA was significantly higher than that in the MRO(P<0.05).The relative abundance of Butyrivibrio in the rumen epithelium of MRC and MCA was significantly lower than that of MRO(P<0.05).Experiment 4: Effects of different diets on gene expression of ruminal epithelium in 20~60 days-old goat kidsThis study was designed to investigate the effects of different diets on gene expression of ruminal epithelium in 20~60 days-old goat kids.Trial design was the same as experiment 1.At the age of 60 days of goat kids,one healthy goat kid,weighing close to the average body weight,was slaughtered for each treatment.The rumen epithelium was collected for transcriptome sequencing,and the expression of epithelial gene was measured.The results of GO enrichment showed that the differentially expressed genes in the MRO-vs-MCA were mainly enriched into biological process regulation,developmental process regulation,anatomical structure development,and multicellular biological development.The differentially expressed genes in the MRO-vs-MRC were mainly enriched into the intrinsic components of the membrane,the integral components of the membrane,and the multicellular biological processes.The differentially expressed genes in the MRC-vs-MCA were mainly enriched in organic cyclic compound binding,heterocyclic compound binding,and carbohydrate derivative binding.The results of KEGG enrichment showed that the differentially expressed genes in the MRO-vs-MCA were mainly enriched in pathways in cancer,PI3K-Akt signaling pathway,and human papillomavirus infection.MRO-vs-MRC differentially expressed genes are mainly enriched in human papillomavirus infection,PI3K-Akt signaling pathway,and cell adhesion molecules.The differential gene of MRC-vs-MCA is mainly enriched in cytokine-cytokine receptor interaction,platelet activation,cell adhesion molecules.The expression levels of ketogenic genes such as HMGCL,HMGCS2 and BDH1 in MCA and MRC were significantly higher than those in MRO(q<0.05).However,the expression levels of IGFBP4 and IGFBP2 in MRC and MCA were significantly lower than those in MRO(q<0.05).There was a significant positive correlation between the expression of HMGCL,HMGCS2 and BDH1 and the contents of acetate,propionate and butyrate in rumen fluid(P<0.01).The results showed that feeding concentrates or concentrates+ alfalfa pellets at the 20~60 day age of goat kids increases the content of acetate,propionate and butyrate in the rumen fluid of kids.Acetate,propionate and butyrate promoted the expression of ketogenic gene in rumen ventral sac of goat kids and improved the ketogenic ability.In addition,feeding concentrates or concentrates+ alfalfa pellets reduced the expression of IGFBP4 and IGFBP2 and promoted the proliferation of epithelial cells.In summary,in the 20~60 day-old stage of goat kids,feeding concentrates or concentrates+ alfalfa pellets promoted the establishment of dominant bacteria in the rumen of goat kids and increased similarity of flora,which made the rumen microbial composition of kids closer to adult goats.At 20~60 days of age,feeding concentrates or concentrates+ alfalfa pellets increased the proportion of fibrolytic and proteolytic bacteria in the rumen of the goat kids and improved the rumen fermentation function.At 20~60 days of age,feeding concentrates or concentrates+ alfalfa pellets increased the content of acetate,propionate and butyrate in the rumen and promoted the expression of ketogenic genes such as HMGCL,HMGCS2 and BDH1,increased rumen ketogenic capacity,and provided sufficient energy for rumen development.On the other hand,feeding concentrates or concentrates+ alfalfa pellets significantly reduced the expression of IGFBP2 and IGFBP4,decreased the inhibitory effect of IGFBP2 and IGFBP4 on IGF,and promoted the proliferation of rumen epithelial cells.