Response Of Weaning Pigs To Enterotoxigenic Escherichia Coli(K88) Challenge When Fed Diets Containing Mixture Of Formic Acid And Propionic Acid

The experiment was conducted to evaluated the optimal dosage of the mixture of formic acid and propionic to protect the weaning pigs from enterotoxigenic Escherichia coli infection.Thirty weaning pigs(Duroc × Landrace × Yorkshire,average weight 7.5 ± 0.5 kg)were randomly allocated to 6 dietary treatments:(1)basal diet(CON);(2)basal diet with antibiotics(50 mg/kg quinocetone,75 mg/kg chlortetracycline,50 mg/kg kitasamycin;ATB);(3)basal diet with 0.6% LC(mixture of 64% formic acid and 25% propionic aicd;0.6%);(4)basal diet with 0.8% LC(0.8%);(5)basal diet with 1.0% LC(1%);(6)basal diet with 1.2% LC(1.2%).In each treatment,there were five replicates with one piglet per replicate.The experiment period was 17 days,3 days of adaptation,7 days of feeding differet treatment diets,piglets orally challenged with ETEC on day 11.After challenge,the blood samples were collected and the rectal temperature(RT)and fecal scores of piglets were monitored at 0 h,9 h,24 h,48 h,96 h and 168 h.The fresh feces samples were collected at 0 h,24 h,and 48 h postchallenge and the microbial counts in feces were measured.The results were as follows:1.Rectal temperature and fecal scores: supplementation of ATB,0.8% LC and 1.0% LC induced lower RT at 24 h postchallenge(P < 0.05)and with addition of ATB,0.6% LC,1.0% LC and 1.2% LC,RT appeared lower compared with CON group(P < 0.05).After challenge,within CON group,higher FS was observed at 9 h and 24 than 0 h(P < 0.05),which was not appeared in other treatments(P > 0.05).At 9 h postchallenge,compared with CON group,FS in ATB,1.0% LC and 1.2% LC group was higher(P < 0.05),which didn’t differ from 0.6% LC and 0.8% LC group(P > 0.05).2.Plasma TNF-α concentration: At 24 h postchallenge,plasma TNF-α was lower in ATB,1.0% LC,1.2% LC group than CON,0.6% LC,0.8% LC group(P < 0.05).All additive treatments decreased the plasma TNF-α contration at 48 h postchallenge(P < 0.05).3.Plasma IFN-γ concentration: At 24 h postchallenge,plasma IFN-γ concentration in 1.0% LC and 1.2% LC group was lower than CON and 0.6% LC group(P < 0.05),which wasn’t significantly different with ATB group(P > 0.05).4.Plasma IL-1β concentration: After challenge,diets with ATB,1.0% LC and 1.2% LC caused a decrease of the concentration of IL-1β at 24 h and 48 h postchallenge(P < 0.05).5.Plasma IL-6 concentraition: In pasma,IL-6 concentration appeared higher in CON,0.6% and 0.8% group than ATB,1.0% LC and 1.2% LC group at 24 h postchallenge(P < 0.05).All additive treatments decreased the IL-6 concentration at 48 and 96 h postchallenge(P < 0.05),except 0.6% LC treatment at 96 h postchallenge.6.Plasma IL-10 concentration: The ATB,1.0% LC and 1.2% LC treated piglets showed lower plasma IL-10 concentration than CON,0.6% LC and 0.8% LC groups(P < 0.05).At 48 h postchallenge,lower plasma IL-10 concentration was observed in 0.8% LC,1.0% LC and 1.2% LC group(P < 0.05).7.Microbial counts in feces: There was no effect of treatment on fecal total coliforms and Lactobacillus counts observed at 0,24 and 48 h after challenge(P > 0.05).In summary,administration the mixture of formic acid and propionic acid alleviated the inflammatory response of weaned pigs challenged with ETEC K88 and then reduced febrile and diarrhea.The recommended dosage of the mixture of formic acid and propionic acid was 1%,which was comparable to antibiotics,can be considered an effective alternative to antibiotics when piglets under ETEC challenge.