| As a potential alternative to antibiotics,phages play an important role in combating bacterial resistance.The purpose of this study was to evaluate the effects of phage on growth performance,intestinal mucosal physiology and barrier function in weaned piglets.A total of 120 piglets were allocated randomly to four dietary treatment groups and fed a basal diet(control group)or a basal diet containing 200,400 and 600 mg/kg bacteriophage for 21?days,respectively.Experiment 1: Piglets were weighed at the beginning and end of the feeding experiment,and fasted for 12 hours before weighing.During the test period,the feed consumption of each group of piglets was recorded in detail.After the experiment,the piglet growth performance and other related indicators were calculated.At 8:00 am on the day of the end of the breeding experiment,a piglet was selected from each group to perform anterior vena cava blood collection and fasted for 12 hours before blood collection.Blood samples were collected after centrifugation.The results showed that: 1)Compared with the control group,the piglet weight of the 400 mg/kg and 600 mg/kg phage groups increased significantly(P<0.05);the 400 mg/kg phage group significantly reduced the feed-to-weight ratio and the frequency of diarrhea(P<0.05).In addition,with the increase of the amount of dietary phage,the diarrhea frequency and diarrhea index of piglets showed a quadratic curve change(P =0.024 and P = 0.015).2)Compared with the control group,the serum IL-10 content of piglets in the 400mg/kg phage group was significantly increased(P<0.05),and the levels of IL-1βand TNF-α were significantly decreased(P <0.05).Experiment 2: At 8:00 am on the day of the end of the breeding test,a piglet was selected from each group to perform anterior vena cava blood collection and fasted for 12 hours before blood collection.Blood samples were collected after centrifugation.After the piglets were slaughtered,the jejunum and ileum were removed from the abdominal cavity,and the intestinal mucosa was scraped and packed in a numbered sterile cryopreservation tube,and stored in a-80℃ refrigerator.The duodenum,jejunum,and middle ileum were isolated for paraffin section.The results showed that: 1)Compared with the control group,the 400 mg/kg phage group significantly increased V: C in the duodenum,jejunum and ileum of piglets(P<0.05).2)Compared with the control group,the 400 mg/kg phage group can significantly reduce the content of serum D-Lactate and DAO(P<0.05).3)Compared with the control group,the 400 mg/kg and 600 mg/kg phage groups can significantly increase the expression of Claudin-1,Occludin and ZO-1 m RNA in the jejunum mucosa(P<0.05);Increase the expression of Occludin protein in the jejunal mucosa(P<0.05).4)Compared with the control group,the 400 mg/kg phage group can significantly increase the expression of TLR-2,TLR-4 m RNA,and TLR-9 m RNA in the jejunal mucosa(P<0.05).5)The contents of s Ig A,TGF-α and ITF in the ileal mucosa in the 400 mg/kg and 600 mg/kg phage groups were significantly higher than those in the control group(P<0.05).Experiment 3: At the end of the test,a healthy and near-average piglet was slaughtered from each replicate,and the p H of the contents of the duodenum,jejunum,ileum,and cecum was measured with a p H meter after slaughter.At the same time,part of the duodenum and jejunum were separated,and the intestinal mucosa was scraped,numbered and packed in sterile cryopreserved tubes,and then placed in a-80°C refrigerator.Then take the middle intestine and colon of the cecum,ligate both ends and put them in liquid nitrogen,then transfer to-80℃ refrigerator.The results showed that: 1)Compared with the control group,the 400 mg/kg phage group could significantly reduce the piglet’s ileum p H(P<0.05).2)Compared with the control group,the phage group at 400 and 600 mg/kg significantly increased acetic acid,butyric acid and total acid in the cecum of the piglets,and the content of acetic acid and total acid in the colon(P<0.05).4)Compared with the control group,In the 400 mg/kg phage group,the duodenum mucosa sucrase and lactase activity of the piglets increased significantly(P<0.05),and the jejunal mucosa maltase activity increased significantly(P<0.05).Experiment 4: At the end of the test,a healthy and near-average piglet was slaughtered from each repeat,the abdominal cavity was dissected,the cecum was quickly separated,and the intestine with chyme was cut.The 16 S rRNA sequence of piglet intestinal microbial bacteria was obtained by extracting the genomic DNA of intestinal microorganisms of weaned piglets in different treatment groups and then specifically amplified by PCR.The amplified sequence was sequenced using Mi Seq high-throughput sequencing technology.To study the effect of bacteriophage on the composition of cecum microflora in weaned piglets.The results showed that: 1)The richness of the flora and the uniformity of species composition in the piglet blind content were higher in the 400 mg/kg and 600 mg/kg phage groups.2)With the increase of the amount of phage,the similarity of the cecum content flora is getting lower and lower,and the 600 mg/kg phage group is the lowest.3)At the level of phylum,the thick-walled phylum,Proteobacteria,and Bacteroides are the dominant flora.Compared with the control group,the contents of actinomycetes in each bacteriophage group were significantly reduced(P<0.05),and Bacteroides were significantly increased(P<0.05).At the genus level,Ruminococcaceae is the dominant genus.Compared with the control group,the 600 mg/kg phage group significantly increased the level of Ruminococcaceae(P<0.05).4)Correlation analysis of cecum flora structure and metabolites in weaned piglets showed that the relative abundance of Lactobacillus was positively correlated with propionic acid and butyric acid(P<0.05,R> 0.6).In summary,the addition of phage to the diet can improve the growth performance of weaned piglets and reduce the diarrhea index.And it has a certain role in improving the morphology and function of the small intestine of piglets,at the same time,it can regulate the activity of intestinal digestive enzymes,improve the structure of intestinal microorganisms,and promote intestinal health of piglets.Among them,phage dose of400mg/kg was the best. |
