Effects Of ZnO Nanoparticles On The Intestinal Microbiota And Mucosal Immunity Of Weaned Piglets

In modern animal husbandry industry,pharmacological dose of dietary ZnO(>2000 mg Zn/kg)has been widely used due to its efficient function on promoting growth and relieving diarrhea of weaned piglets.But pigs consume relatively higher level of Zn will excrete more in urine and feces,which raises concerns on environmental pollution and causes negative evaluation of ZnO using in weaned piglets diet.Zinc oxide nanoparticles are an inorganic zinc product ranging in particle size from 1 to 100 nm.To understand the effects of Zinc oxide nanoparticles,as a substitute for traditional Zinc oxide and coated Zinc oxide,on improving host health of the early-weaned piglets,as well as their mechanisms,we examined the the influence of them on gut microbiota and mucosal immunity using a weaned piglet model.In Exp.1,a total of 120 cross-bred piglets,weaned at 28 d,were randomly allocated for four groups treated with a control ration,or supplemented with 2000 mg Zn/kg traditional Zinc oxide,or 500 mg Zn/kg coated Zinc oxide,or 500 mg Zn/kg Zinc oxide nanoparticles,respectively.During the animal experiment,the growth performance and diarrhea incidence were determined.On 42 d,the intestinal tissue and serum samples were collected to test intestinal permeability,intestinal morphology,inflammatory indicator,and barrier immunity function.The results revealed that Zinc oxide nanoparticles treated piglets had better growth performance and reduced diarrhea incidence(P<0.05),same as coated Zinc oxide,and accompanied with decreased intestinal permeability and improved mucosal morphology.The expression of the tight junction protein Claudin-1?Claudin-3?Claudin-5 and Occludin in both ileal and colonic tissue was changed in the Zinc oxide nanoparticles treatments(P<0.05).Meanwhile,Zinc oxide nanoparticle modified the expression of Lgr5 and Bmil,which are the marked proteins of intestinal stem cells.In Exp.2,on 42 d,the gut chymes were collected to test intestinal microbiota and the concentration of SCFAs and to determin the changes of concentrateion of GPR41 by immunoblotting analysis in ileum and colon.Gene sequencing analysis of 16S rRNA showed a distinction of bacterial richness and diversity,as well as bacterial community structure between ileum and colon.Dietary Zinc oxide nanoparticles improved the the abundance and diversity of bacteria in foregut.With the treatment of Zinc oxide nanoparticles,the abundance of Actinobacteria in ileum dramatically decreased,as well as Proteobacteria.And the concentration of main SCFAs in colon increased,such as acetic acid,propionic acid and butyric acid,which may be activated by the concentration of GPR41.Our findings indicated that low-dose Zinc oxide nanoparticles(500 mg Zn/kg)could reduce diarrhea and improving the performance of piglets,which is similar to high-dose traditional zinc oxide(>2000 mg Zn/kg).And it is able to improve the intestinal mucosal barrier function and local mucosal immunity by improving the microbial flora structure of weaning piglets.