Study On Gastrointestinal Tract Development And Microflora Characteristics Of Xinong Saanen Dairy Goat Kids

In this experiment,14 day old Xinong Saanen dairy goat kids were used to study the effects of different levels of neutral detergent fiber（NDF）on their growth and development,serum biochemical indicators,slaughter performance,apparent digestibility of nutrients,gastrointestinal development and microbial flora.Sixty well-developed dairy goat kids of the same age with a weight close to（3.7±0.20 kg）were selected for the experiment.Randomly divided into three groups:（20N）20%NDF,（25N）25%NDF,and（30N）30%NDF.The experimental period is 14-84 days old for dairy goat kids.Including 3 experiments.1.The effect of different NDF levels on the growth and development,apparent nutrient digestibility,serum biochemical indicators,and slaughter performance of dairy goat kids.During the trial period,daily food intake was recorded and weighed every two weeks.Blood samples of goat kids were collected on an empty stomach 1 hour before morning feeding every four weeks to measure serum biochemical indicators;Seven days before the end of the trial period,the apparent digestibility of nutrients was measured through a digestion and metabolism test.After the trial period,three dairy goat kids with similar average body weight were selected for slaughter,and their slaughter performance and weight of various tissues and organs were measured.The results showed that there was no significant difference in body weight among the three groups of dairy goat kids aged 14-84days（P>0.05）,while the daily weight gain of the 30N group dairy goat kids aged 14-28days was significantly higher than that of the other two groups（P<0.05）;The feed intake of the 28-42 day old 20N group dairy goat kids was lower than that of the 25N group and the30N group（P<0.01）.2)There was no significant effect of different NDF levels on the apparent digestibility of nutrients in goats kids（P>0.05）.3)Under the test conditions,feeding diets with 25%and 30%NDF levels significantly increased the levels of alanine transaminase（ALT）,aspartate transaminase（AST）and serum in dairy goat kidsβ-Hydroxybutyric acid content（P<0.05）.4)The slaughter rate of the 30N group was higher than that of the 20N group（P<0.05）,and there was no significant difference in other slaughter performance indicators and tissue organ weight（P>0.05）.2.The effect of different levels of NDF on the gastrointestinal development of dairy goat kids.Where 84 day old dairy goat kids were fed in the morning and their rumen fluid samples were collected 4 hours after feeding,and the p H value,HN₃-N,and volatile fatty acids of the rumen fluid were measured.After the end of the trial period,three dairy goat kids of similar weight were selected from each group for slaughter.The total weight of the rumen and the weight of each gastric chamber,as well as the weight and length of each small intestine segment,were measured.Tissue samples of the rumen abdominal sac,duodenum,jejunum,and ileum were collected for tissue sectioning.After HE staining,the tissue morphology was observed and relevant indicators were measured.The results showed that feeding different NDF levels of starter had no significant effect on the total weight of the reconstructed stomach and the empty weight of each gastric chamber in dairy goat kids（P>0.05）.The small intestine weight of the 25N and 30N groups was significantly higher than that of the 20N group（P<0.05）.2)As the NDF level of the feed increased,the length and width of the rumen papilla showed an increasing trend,but the difference was not significant（0.05<P<0.1）.The depth of jejunal crypt in the 25N and 30N groups of dairy goat kids was significantly lower than that in the 20 group（P<0.01）,and the V/C value of the jejunum in the 25N and 30N groups of dairy goat kids was significantly higher than that in the 20N group（P<0.01）;The thickness of the ileal muscle layer in the 25N and 30N groups was significantly higher than that in the 20N group（P<0.05）.3)Cellulase in the rumen and small intestine showed an increasing trend with increasing NDF levels（0.05<P<0.1）α-Amylase,pepsin,and small intestineα-The content of amylase and chymotrypsin was significantly higher than that of the other two groups（P<0.05）.4)The p H value of rumen fluid in the 25N and 30N groups of dairy goat kids was significantly higher than that in the20N group（P<0.05）;The acetic acid concentration in the rumen fluid of the 30N group was significantly higher than that of the 20N group（P<0.05）;The concentration of butyric acid in the rumen fluid of the 30N group dairy goat kids was significantly increased compared to the 20N and 25N groups（P<0.01）;The concentration of total volatile fatty acids（TVFA）in gastric juice of the 30N group was significantly higher than that of the 20N and 25N groups（P<0.05）.3.The effect of different NDF levels on the gastrointestinal microflora of dairy goat kids.After the end of the trial period,three dairy goat kids with similar weight were selected and slaughtered.The contents of rumen,jejunum and cecum of dairy goat kids were collected,and the microflora was determined by 16Sr RNA technology.The results showed that there was no significant difference in alpha and beta diversity of rumen and cecal bacteria between different NDF levels（P>0.05）.There was no significant difference in alpha diversity of jejunal bacteria among different NDF levels（P>0.05）,but there was a significant impact on Beta diversity（P<0.05）.At the phylum level,the dominant microbiota in the rumen are Firmicutes and Bacteroidetes,the dominant microbiota in the jejunum are Firmicutes and Actinobacteria,and the dominant microbiota in the cecum are Firmicutes.The results of species difference analysis at the genus level showed that there was a significant enrichment of Lachnospiraceae＿UCG-010,UCG-010,and norank＿f＿＿UCG-010 with fiber decomposition characteristics in the rumen of the 30N group of dairy goat kids.In the 20N group,there was a significant enrichment of Clostridia＿vadin BB60＿group and norank＿o＿＿Clostridia＿vadin BB60＿group with fiber decomposition characteristics in the jejunum of dairy goat kids;There was a significant enrichment of unclassified＿f＿＿Lachnospiraceae fibers with fiber decomposition characteristics in the jejunum of 30N group dairy goat kids.To sum up,under the test conditions,feeding diets with 25%and 30%NDF levels signi ficantly increased the levels of glutamic acid transaminase（ALT）,glutamic acid transaminas e（AST）and serum of dairy goat kidsβ-Hydroxybutyric acid content;It increased the weigh t of the small intestine and the V/C value of the jejunum,as well as the content of acetic aci d,butyric acid,and total volatile fatty acids in the rumen;The relative abundance of Lachnos piraceae＿UCG-010,UCG-010,and norank＿f＿＿UCG-010 with fiber degrading activity in the rumen was increased,and the relative abundance of Clostridia＿vadin BB60＿group,norank＿o＿＿Clostridia＿vadin BB60＿group,and unclassified＿f＿＿Lachnospiraceae with fiber degradin g activity in the small intestine was increased.Therefore,NDF level of 25%-30%is more su itable for starter diets.