The Effects of Dietary Porous Zinc Oxide Supplementation on Growth Performance, Inflammatory Cytokines and Tight Junction's Gene Expression in Early-Weaned Piglets.

This study was conducted to investigate the effect of dietary porous ZnO supplementation on the growth performance, inflammatory cytokines and tight junction's gene expression in weaned piglets. A total of 192 weaned piglets were randomly allocated to 4 experimental groups (n=48/group) and fed, during 14 d, with one of the following dietary treatments: 1) basal diet (NC); 2) basal diet with 3,000 mg/kg of conventional ZnO (PC); 3) basal diet with 750 mg/kg of porous ZnO (low inclusion porous ZnO, LP-ZnO); 4) basal diet with 1,500 mg/kg porous ZnO (high inclusion porous ZnO, HP-ZnO). Results showed that dietary supplementation with regular ZnO or porous ZnO (750 and 1,500 mg/kg) improved average daily gain (ADG), feed to gain ratio (F/G) and jejunum morphology, while decreasing diarrhea incidence. Compared with the NC group, porous ZnO at both doses (750 or 1,500 mg/kg) increased serum alkaline phosphatase (ALP), immunoglobulin G (IgG) and insulin-like growth factor 1 (IGF-1) concentrations, but decreased serum glucose (GLU). Moreover, the mRNA expression of anti-inflammation cytokine (TGF-ß), tight junction (Occludin, ZO-1) in the jejunum by different ZnO administration were significantly increased compared with the NC group, while mRNA expression of pro-inflammatory (IL-8), membrane channels that transport water (AQP3) and miR-122a were significantly decreased. It can be concluded that porous ZnO even at low dose (750 mg/kg) can be an effective alternative to pharmacological (3,000 mg/kg) conventional ZnO in reducing diarrhea, promoting the growth performance, increasing anti-inflammatory cytokines and tight junctions, reducing pro-inflammatory cytokines of weaned piglets.

Effect of zinc oxide sources and dosages on gut microbiota and integrity of weaned piglets.

Zinc oxide (ZnO) supplied at pharmacological dosage in diets of weaned piglets improves growth performance. However, it causes environmental contamination and induces bacterial antibiotic resistance, yet this practice is debated. The effects on gut microbiota and integrity in weaned piglets of conventional ZnO at nutritional and pharmacological dosage (110 and 2,400 mg/kg Zn, respectively) were compared to an alternative ZnO source at 110 and 220 mg/kg Zn. Each of the four treatments was applied to four pens (two piglets/pen; weaning age, 20 days) for 15 days, and piglets were sampled on day 15 to determine indices of gut integrity. Feeding conventional ZnO at 2,400 mg/kg Zn reduced coliforms and Escherichia coli in distal small intestine as compared to conventional ZnO at 110 mg/kg (-1.7 and -1.4 log10 cfu/g, respectively), whereas the alternative ZnO reduced only coliforms, irrespective of dosage (-1.6 to -1.7 log10 cfu/g). Transepithelial electrical resistance of distal small intestinal mucosa was higher for pigs fed the alternative ZnO source as compared with groups fed 110 mg/kg Zn of conventional ZnO, in line with a trend for higher gene expression of claudin-1 and zona occludens-1. Interestingly, the alternative ZnO source at 110 and 220 mg/kg Zn increased intestinal alkaline phosphatase gene transcript as compared to conventional ZnO at 110 mg/kg Zn, whereas the alternative ZnO source at 110 mg/kg Zn exhibited higher Zn concentrations in mucosa (2,520 µg/g) as compared to conventional ZnO at 110 mg/kg Zn (1,211 µg/g). However, assessing alkaline phosphatase activity, no significant effects were found. In conclusion, the alternative ZnO reduced digesta Enterobacteriaceae numbers and improved gut integrity, albeit similar or better, depending on the dosage, to the effects of pharmacological dosage of conventional ZnO.