Effects Of Antimicrobial Peptides Or Tannic Acid As Zinc Oxide Substitutes On Growth Performance,diarrhea,and Fecal Microbiota In Weaned Piglets

Zinc oxide(Zn O)has been widely used to treat diarrhea during the weaning process.However,Zn O also poses a serious environmental burden,and an increasing number of countries have restricted their use as feed additives in weaned piglets.Therefore,there is an urgent need to find safe and effective alternatives for the prevention and treatment of diarrhea in weaned piglets.The minimum inhibitory concentrations of Zn O,antimicrobial peptide(AMPs)and tannic acid(TA)against Enterotoxigenic Escherichia coli(CCVC 1570),Salmonella(CCVC 3374)and Staphylococcus aureus(CCVC 1882)were first measured to evaluate their inhibitory efficacy.Secondly,Zn O,AMPs and TA were then supplemented in the diets to determine growth performance,diarrhea,antioxidant capacity,immune function and intestinal microorganisms of weaned piglets.Thirty 28-day-old Duroc × Landrace ×Yorkshire weaned piglets(male)weighing 7.42±0.88 kg were randomly divided into 3groups: Zn O group(basal diet + 2000 mg/kg Zn O),AMPs group(basal diet + 700mg/kg AMPs),and TA group(basal diet + 1000 mg/kg TA).There were 10 replicates in each group with 1 pig in each replicate.The experimental pre-trial period was 3 days,and the trial period was 28 days.The results showed that:(1)TA showed the best combined inhibitory effect on the three pathogenic bacteria,with a minimum inhibitory concentration of 1 mg/m L for Enterotoxigenic Escherichia coli and Staphylococcus aureus and 0.5 mg/m L for Salmonella.(2)There were no significant differences in growth performance,diarrhea rate and diarrhea index among the 3 groups(P>0.05).(3)The apparent digestibility of dry matter and organic matter of weaned piglets in the AMPs and TA groups were higher than that in the Zn O group(P<0.05),the apparent digestibility of crude fat of weaned piglets in the AMPs group was higher than that in the Zn O group(P<0.05).(4)The plasma ALT activity of weaned piglets in the Zn O and TA groups was significantly higher than that in the AMPs group at d 28(P<0.05);Meanwhile,the plasma GH levels of weaned piglets in the Zn O and AMPs groups were significantly higher than those in the TA group(P<0.05).(5)The plasma Ig M levels of weaned piglets in the Zn O and AMPs groups were significantly higher than that in the TA group at d 28(P<0.05).(6)There was no significant difference in plasma IL-2,IL-6 and IL-8 levels among the three trial groups of weaned piglets at d 14(P>0.05);The plasma IL-6 levels of weaned piglets in the Zn O and AMPs groups were significantly higher than those in the TA group at d 14(P<0.05).(7)There were no significant differences in plasma T-AOC,CAT,T-SOD,GSH-Px activities and MDA levels among the 3 groups at days 14 and 28 of experiment(P>0.05).(8)The Chao1 and ACE indices of weaned piglets in the AMPs group were significantly higher than those in the Zn O group(P<0.05);Firmicutes and Bacteroidetes were the most dominant phyla in all samples;and the relative abundance of lachnospiraceae of weaned piglets in the TA group was significantly higher than that in the Zn O group(P<0.05);The relative abundance of Rikenellaceae of weaned piglets in the TA group was higher than that in the AMPs group(P<0.05);The relative abundance of Acidaminococcaceae of weaned piglets in the Zn O group was higher than that in the TA group(P<0.05);The relative abundance of the genus Treponema＿2 of weaned piglet in the TA group was higher than that in the Zn O group(P<0.05);Compared with Zn O groups,the relative abundance of Prevotellaceae NK3B31 of weaned piglets in AMPs and TA groups were lower(P<0.05),and the relative abundance of Lachnospiraceae XPB1014 were higher(P<0.05).To sum up,TA had the best antibacterial effects against the bacterial pathogens tested;the growth performance,diarrhea rate and diarrhea index of weaned piglets were similar among 3 groups;compared with Zn O,AMPs could increase the intestinal microbiota richness of the weaned piglets and improve the fecal microbiota profiles.Therefore,AMPs and TA can be added to the diet of weaned piglets as an alternative to Zn O to reduce diarrhea,improve fecal microbiota profiles and growth performance.