Dietary zinc oxide nanoparticles as growth promoter for weanling pigs

The purpose of this study was to evaluate the effects of dietary graded levels of zinc oxide nanoparticles (ZnO-N) on weanling pigs' growth performance, nutrient and energy digestibility, fecal Zn excretion, diarrhea occurrence, blood parameters, organ weights, and intestinal bacteria count. One hundred and sixty 21-d weaned castrated male and female pigs (5.89 ± 0.82 kg initial BW) were used in a randomized complete block design experiment with 5 treatments, 8 replications per treatment, and 4 pigs per experimental unit (pen). The treatments were: negative control - corn-soybean meal basal diets with 125 mg ZnO/kg; positive control - basal diet with 3000 mg conventional ZnO/kg (150 ± 82.5 nm); and basal diet with 15, 30 or 60 mg ZnO-N/kg (70 ± 38.6 nm). Pigs were fed dietary treatments from 1 to 21 d, followed by a common diet (same diet for all treatments) from 21 to 35 d feeding period. On d 19 of the experiment, blood samples were collected from one castrated male of each pen to determine blood parameters. On d 21 of the experiment, the animal used in blood collection was slaughtered to evaluate organ weights and intestinal bacterial count. ANOVA and orthogonal contrasts were performed to determine the dose-response of each variable to dietary ZnO-N levels (0, 15, 30 and 60 mg/kg), and to compare positive control with negative control and with each dietary ZnO-N level. No effects of dietary ZnO-N levels were observed on growth performance, except for G:F and diarrhea occurrence that improved linearly during 1-7 d. Fecal Zn excretion, blood parameters, organ weights, and intestine bacteria count were not affected by dietary ZnO-N-levels, but linearly increased plasma Zn concentration. Increasing dietary ZnO-N levels linearly increased nutrient and energy digestibility, as well as the pharmacological dose of conventional ZnO control. From 1-21 d experimental period lower ADFI was observed for ZnO-N levels and negative control compared to positive control, while no differences among treatments were observed on performance and diarrhea occurrence during the 21-35 d experimental period. Lower fecal Zn excretion and lower plasma Zn concentration were observed for ZnO-N levels and negative control compared to positive control. Overall, both low dietary ZnO-N levels and pharmacological conventional ZnO dose were not effective in improving performance of weanling pigs, although some post-weaning diarrhea control was observed.