| Suckling period is one of the key stages of growth and development of calves.Higher daily weight gain and weaning weight during suckling period will help improve the profitability of dairy cows at the production stage.However,nutritional imbalances,diseases,and microbial disorders can significantly affect the growth of pre-weaning calves.Studies have shown that supplementation of prebiotics can regulate gut microbiota,improve growth performance and enhance resistance to disease.Oat β-glucan,one of the cell wall polysaccharides of oats and other grains,is a soluble fiber that is considered a prebiotic when added to feed to benefit the growth and health of suckling calves.However,currently There are few reports on the effects of oat β-glucan on the intestinal health of lactating calves.Therefore,it is of great practical significance to integrate the microbiota,plasma metabolites and serum biochemical indices to clarify the effects of oat β-glucan on the growth and health of pre-weaning dairy cows by regulating the microbiota and host metabolism,and provide a basis for the application of oat β-glucan as a prebiotic in pre weaning calves.In this study,14 healthy newborn Holstein calves with similar age and body weight were randomly divided into control group(n=7)and β-glucan group(n=7),and weighed.On day 7,calves in the β-glucan group were fed a basal diet supplemented with oat β-glucan(calculated at 75mg/kg body weight)for 14 days.Before morning feeding on day 21,blood and fecal samples of calves in control group and β-glucan group were collected.Serum biochemical indexes were analyzed,fecal microbiota was analyzed by 16 SrDNA amplification sequencing,and plasma metabolites were analyzed by high performance liquid chromatography-tandem mass spectrometry(LC-MS/MS).On day 60,calves are weaned and weighed before morning feeding.The results of the experiment are as follows:1.Compared with the control group,the serum total protein,albumin and globulin in β-glucan group showed increasing trends(P<0.1),and the serum superoxide dismutase activity was significantly increased(P<0.05).The activity of diamine oxidase tends to increase(P<0.1).There was no significant difference in the levels of glutathione and malondialdehyde between the control group and the beta-glucan group(P>0.05).No significant difference in lipopolysaccharide concentration(P>0.05).The average daily gain from birth to weaning of suckling calves in the β-glucan group increased by 70 g/d(P>0.05),and the weaning weight increased by 4.29 kg(P>0.05).The results show that oat β-glucan can increase the levels of total protein,albumin,and globulin in serum of lactating calves,significantly increase the activity of oxide dismutase,and enhance the activity of diamine oxidase.2.Compared with the control group,Shannon index,Chao 1 index and Simpson index of intestinal bacteria in β-glucan group were significantly increased(P< 0.05).Firmicutes,Actinobacteria and Bacteroidetes were the main groups in the intestinal tract of each weaned calf(> 90%),and the difference was not significant(P> 0.05).The abundance of Cyanobacteria in β-glucan group was significantly higher than that in control group(P< 0.05).The ratio of Firmicutes to Bacteroidetes was lower than that of the control group.STAMP variance analysis showed that the abundance of Alloprevotella,Alistipes,Bacteroides and Phascolarctobacterium in β-glucan group was significantly increased(P< 0.05).The abundance of CL500-29 marine group,Campylobacter,Hyphomicrobium,Glutamicibacter,Sphingorhabdus and Marvinbryantia in β-glucan group was significantly decreased(P< 0.05).The results showed that feeding oat β-glucan could increase the richness and diversity of gut microbiota of suckling calves,decrease the harmful bacteria such as Campylobacter in the gut microbiota of suckling calves,and increase the relative abundance of beneficial bacteria such as Bacteroides,Mycobacteria,Prevoiformis,Fornirella,Spiralis vitriformis and koala bacillus.3.Compared with the control group,the plasma contents of L-tyrosine,α-trehalose,Lhistidine,phenylacetic acid,2-oxalic acid and N6,N6,N6-trimethyl-L-lysine of calves in β-glucan group were increased(P<0.1).Twenty metabolites,such as glycine deoxycholic acid,glycine deoxycholic acid,sphingosine,L-canine,5-hydroxyindoleacetic acid,were reduced(P<0.1).KEGG pathway analysis showed that tryptophan metabolism,aminoacyl t RNA biosynthesis and β-alanine metabolism had significant changes.Based on Spearman correlation analysis,the abundance of Ruminiclostridium＿NK4A214 was positively correlated with the levels of 3-Methoxy-4-Hydroxyphenylglycol and sphingosine,and negatively correlated with trehalose.However,the abundance of Alistipes was negatively correlated with the levels of 3-Methoxy-4-Hydroxyphenylglycol and sphingosine,and positively correlated with trehalose..The abundance of Bacteroides was positively correlated with trehalose levels,and negatively correlated with 3-methoxy-4-hydroxyphenyleneglycol sulfate and sphingosine levels.The results showed that adding oat β-Glucan to the diet can increase the content of trehalose and histidine in the plasma of lactating calves,reduce the content of caninurenine,5-hydroxyindoleacete,glycine deoxycholic acid,glycine goose deoxycholic acid,and down regulate the metabolism of tryptophan;Oat β-Glucan can affect plasma metabolism and growth performance by regulating the abundance of Ruminococcus,Streptomyces,and Bacteroides in the gut of lactating calves.Conclusion:(1)Adding oat β-Glucan to the diet can increase the levels of total protein,albumin,and globulin in serum of lactating calves,increase SOD levels,enhance DAO activity,and improve growth performance;(2)Add oat β-Glucan can enhance the richness and diversity of gut microbiota in lactating calves,increase beneficial gut microbiota,reduce harmful microbiota,and enhance gut barrier;(3)Add oat β-Glucan can increase the content of trehalose and histidine in the plasma of lactating calves,reduce the content of caninurenine,5-hydroxyindoleacete,glycodeoxycholic acid,and glycochenodeoxycholic acid,and lower the metabolism of tryptophan,affecting the level of plasma metabolism;(4)Oat β-Glucan regulates the gut microbiota of lactating calves,affects plasma metabolism levels and serum biochemical indicators,thereby improving growth performance. |
