Effects Of Dietary Supplementation With Rapeseed Peptide On Growth Performance,Antioxidant Function,Immune Function,and Intestinal Microflora Of Weaned Piglets

Rapeseed peptides(RSP)is a group of peptide mixtures with biological activities obtained after the hydrolysis of rapeseed protein.Rsp has the characteristics of small molecular weight,balanced amino acid composition,abundant content,and easy absorption,which has high application value.Our study aimed to investigate the effect of dietary supplementation with rapeseed peptide on growth performance,diarrhea rate,nutrient apparent digestibility,nutrient metabolism indexes,serum antioxidative indexes,serum immune indexes,and fecal microorganism of weaned piglets.The purpose of this study was to investigate the application effect and mechanism of RSP in weaned piglets,which provided more ideas on the application of RSP as plant protein raw materials in weaned piglets.The experiment consisted of two parts: Experiment 1.DPPH and ATBS free radical scavenging rates were used to determine the antioxidant activity of Rsp.Experiment 2.A total of 60 DYL weaned piglets(9.38±0.18 kg)aged 33-35 days were randomly divided into 3 dietary treatment groups,with 5 replicates per group and 4 piglets per replicate.Weaned piglets in the control group(NC)were fed with basal diet,and the weaned piglets in Rsp-1 group and Rsp-2 group were fed the basal diet supplemented with 1% and 2% RSP(Isonitrogenous and isoenergetic substitution),respectively.The feeding experiment lasted 33 days,which was included 5 days acclimatization trial of feeding.The experimental piglets were reared and managed according to routine procedures,and were sterilized by conventional methods.All piglets provided ad libitum access to granular feed(fed pelleted diets)and water,and no concomitant drug therapy was used during the study.The piglets were fed daily at 08:00,12:30 and 18:00 hours.The fecal scores were recorded at 7:00 am and 3:00pm every day according to a 4-grade fecal scoring system.During the experiment,the feed intake was recorded in units of pen.Each piglet was weighed on an empty stomach at 08:00 am on day 1,day 15 and day 29 of the trial.In the morning of the end of the experiment,one pig was randomly selected from each replicate.We collected 10 ml blood from the anterior vena cava and put it into a heparin sodium anticoagulation tube,gently inverted it twice,then immediately centrifuged at 3000r/min for 10 min to separate the serum and stored at-20°C for testing.The fresh feces were collected from several pigs at each pen on the day before the end of the experiment and mixed evenly.Then,divided the feces into three parts and stored in refrigerators at 4℃,-20℃ and-80℃.The feces were used for bacterial counting,nutrient apparent digestibility detection,and microbial composition and relative abundance detection,respectively.The results showed as follows:(1)when RSP concentration was 0.25mg/m L,the DPPH radical scavenging rate was 74%;When RSP concentration was 0.30mg/m L,the radical scavenging rate of ATBS was 93%.The results showed that RSP had free radical scavenging effects in vitro and had a high antioxidant capacity.(2)The results showed that body weight(BW),average daily feed intake(ADFI),and feed to gain(F/G)were not significantly affected by diet supplemented with RSP(P>0.05),however,the average daily gain(ADG)in the Rsp-1 and Rsp-2 group was significantly increased compared with the NC group(0.01<P< 0.05).The diet supplemented with 1% and 2%RSP significantly decreased the diarrhea rate and diarrhea index of weaned piglets(0.01<P< 0.05),and the effect of diet supplemented with 2% RSP on reducing diarrhea rate was significantly higher than that of 1%(0.01<P< 0.05).Compared with the NC group,the diet supplemented with 1% and2% RSP had no significant effects on the nutrient apparent digestibility of ether extract,total phosphorus,and organic matter(P>0.05),but adding 2% RSP could significantly increase the nutrient apparent digestibility of gross energy,crude protein,and calcium(0.01<P< 0.05).There were no significant differences in blood routine indexes of weaned piglets between the Rsp-1,Rsp-2group,and the NC group(P>0.05).Compared with the NC group,the content of serum albumin(ALB)in Rsp-1 and Rsp-2 groups was significantly increased(0.01<P<0.05),and the content of serum total proten(TP)tends to increase by increasing RSP concentration(0.05<P<0.1).Besides,adding 1% and 2% RSP to the diet of weaned piglets could significantly increase the contents of serum Ig A.Adding 1% RSP to the diet of weaned piglets could significantly increase the activities of serum Glutathione peroxidase(GSH-Px)and Catalase(CAT)(0.01<P<0.05),adding 2% RSP also could significantly increase the activities of serum CAT.Compared with the NC group,the addition of RSP had no significant effect on the number of total bacteria,Escherichia coli,yeast,bifidobacteria,and lactobacillus in the feces of weaned piglets(P>0.05),but the number of Lactobacillus had a tendency to increase by increasing RSP concentration(0.05<P< 0.1).Compared with the NC group,the relative abundance of Lactobacillus in the Rsp-1 and Rsp-2 groups was significantly increased(0.01<P<0.05),and the dietary supplementation with 2% RSP could also significantly be improved the fecal bacterial diversity and reduce the relative abundance of Eubacterium＿coprostanoligenes＿group,Treponema＿2,and Coprococcus＿1(0.01<P<0.05).In conclusion,the RSP showed high antioxidant activity in vitro.Dietary supplementation with RSP could improve the growth performance,reduce diarrhea rate,increase nutrient apparent digestibility,increase the serum albumin content,and enhance the immune and antioxidant function of weaned piglets.Also,dietary supplementation with 2% RSP could increase the relative abundance and quantity of beneficial flora such as Lactobacillus,and reduce the relative abundance of harmful bacteria,which indicated that RSP also had positive effects on improve intestinal health of weaned piglets.