Effects Of High-dose Of Zinc Oxide On Growth Performance And Intestinal Health In Weaned Piglets

The aim of this experiment was to evaluate the effects and possible mechanism of high-dose of zinc oxide(Zn O), used as a potential substitute of in-feed antibiotics, on the performance and intestinal health in weaned piglets. One hundred and twenty eight weaned male piglets(21 d-old) were randomly divided into four experiment groups. Four dietary treatments were as follows: basal diets(control), basal diets supplemented with antibiotics(60 mg/kg chlortetracycline + 20 mg/kg colistin sulphate), basal diets supplemented with 2250 mg/kg of Zn O for the first two weeks, basal diets with 2250 mg/kg of Zn O for 4 weeks, respectively.Each treatment group had 8 replicates,with 4 piglets per replicate.The study lasted for 4 weeks. All the piglets were free to water and feed during the experiment. The results were as follows:1. Compared with the control group, the antibiotic group and the high-dose of Zn O for 4 weeks group can significantly increase the average daily gain(ADG) during 1-14 d(P<0.05); High-dose of Zn O for 2 weeks group and antibiotics group significantly decreased the ratio of feed to gain(F/G) during 1-14 d(P<0.05). The ADG, average daily feed intake(ADFI) and F/G in weaned piglets during 14-28 d and 1-28 d of the experiment were not different among these groups(P>0.05). But compared with the antibiotic group and control group, supplementation with high-dose of zinc oxide for 2 weeks or 4 weeks both significantly reduced the diarrhea incidence in weaned piglets during 1-14 d(P<0.05). Moreover, the high-dose of Zn O supplemention for 4 weeks also significantly reduced the diarrhea incidence of weaned piglets during 14-28 d and 1-28 d of the experiment(P<0.05).2. Compared with the control group, supplementation with the high-dose of Zn O for 4 weeks significantly decreased the levels of MDA and increased the activity of plasma GSH-Px at d 14 and 28 in weaned piglets(P<0.05). Compared with the control group, supplemental with high-dose of Zn O for 2 weeks significantly reduced the content plasma of MDA in weaned piglets at d 14 of the experiment(P<0.05); there was no significant difference ratio between these indicators of the high-dose of Zn O for 2 weeks group compared to the control group(P>0.05). In addition, compared with the antibiotic group, supplementation with high-dose Zn O for 2 weeks or for 4 weeks significantly reduced plasma MDA levels in weaned piglets at d 14 of the experiment, while supplementation with high-dose Zn O for 4 weeks also significantly increased the activity of plasma GSH-Px in weaned piglets(P<0.05).3. Compared with the control group,supplementation with high level of Zn O for 4 weeks significantly increased villus heights in the duodenum and ileum, and also reduced duodenal crypt depth in weaned piglets(P<0.05). Moreover, supplementation with high Zn O supplemention for 4 weeks significantly reduce the ratio of villus height to crypt depth in duodenum and jejunum of weaned piglets(P<0.05). The antibiotic group significantly increased the villi heights in the duodenum of weaned piglets(P<0.05), but its villi lower than that of high-dose Zn O for 4 weeks group(P<0.05); there was no significant difference in the above indicators of high-dose of Zn O for 2 weeks group(P>0.05). Compared with antibiotic group, supplementation with high-dose of Zn O for 4 weeks group significantly increased duodenum, jejunum and ileum villus height and the ratio of duodenum, villus height and crypt depth of weaned piglet(P < 0.05), and significantly reduce the duodenal crypt depth(P < 0.05). But the villi height of the duodenum was significantly decreased in supplementation with the high-dose Zn O for 2 weeks group compared with the antibiotic group(P<0.05).4. Compared with the control group, supplementation with high level Zn O for 4 weeks significantly reduced the m RNA expression level of jejunum mucosal inflammatory cytokines IL-1β and IFN-γ, and significantly increased the m RNA expression level of anti-inflammatory cytokine TGF-β, and tight junction proteins ZO-1 and Occudin(P<0.05); Compared with the antibiotic group, the relative expression level of TGF-β(P<0.05) in the jejunum mucosa of weaned piglets was significantly increased compared with supplementation with high-dose Zn O for 4 weeks group. At the same time, compared with the control group, supplementation with high-dose of Zn O group for 2 weeks group and antibiotic group significantly reduce the m RNA expression level of IFN –γ(P<0.05). Compared with the control group, jejunal mucosa of TLR2, TLR4 and MUC2 expression abundances in other groups showed no significant effect(P > 0.05); but compared with the antibiotic group, supplementation with high-dose of Zn O for 2 weeks group significantly reduced the relative m RNA expression level of MUC2 in the ileal mucosa of weaned piglets(P < 0.05). Compared with the control group and antibiotic group, the other two groups had no significant effect on plasma content of Ig G in the weaned piglets(P>0.05).5. Diets with high-dose of Zn O could alter the intestinal microflora structure and decreased the diversity of jejunum and colon in weaned piglets. There was no significant effect in the number of Lactobacillus, Bifidobacterium and Escherichia coli in the total bacterial among treatments(P>0.05). Besides, compared with other groups, the m RNA expression of tet(B) was the highest in the antibiotic group(P>0.05).In conclusion, dietary high-dose of Zn O can significantly decrease the diarrhea incidence, reduce the intestinal inflammation, enhance the intestinal health, and improve the growth performance and antioxidant capacity in weaned piglets.