Evaluation of a microencapsulated form of zinc oxide on weanling pig growth performance, fecal zinc excretion, and small intestinal morphology

Abstract

Abstract A total of 300 pigs (DNA 200 ×400; initially 6.0 ± 0.08 kg BW) were used in a 42-d study to evaluate a microencapsulated form of zinc oxide. At weaning, pigs were randomly allocated to pens and pens randomly assigned to dietary treatments with 5 pigs per pen and 12 pens per treatment. Dietary treatments were: 1) negative control (CON; standard nursery diet containing 110 ppm Zn in the form of zinc sulfate from trace mineral premix); 2) control diet with 400 ppm added Zn from ZnO included in phases 1 and 2 (Low-ZnO); 3) control diet with 3,000 ppm added Zn from ZnO included in phase 1 and 2,000 ppm added Zn from ZnO included in phase 2 (High-ZnO); 4) control diet with 400 ppm added Zn from microencapsulated ZnO included in phases 1 and 2 (Low-MZnO; Vetagro S.p.A., Reggio Emilia, Italy); 5) control diet with 3,000 ppm added Zn from microencapsulated ZnO in phase 1 and 2,000 ppm added Zn from microencapsulated ZnO in phase 2 (High-MZnO; Vetagro S.p.A., Reggio Emilia, Italy). On d 10 and d 28, fecal samples from 2 pigs per pen were collected for fecal Zn concentrations and on d 28, 30 pigs (n = 6) were euthanized, and small intestinal tissues were collected to evaluate morphology. For the entire treatment period (d 0 to d 28) there was no evidence of differences in ADG, ADFI, or G:F (P > 0.05). During the common phase 3 (d 28 to 42) pigs fed the negative control, High-MZnO, or Low-MZnO had improved (P < 0.0001) ADG and ADFI compared to pigs fed High- or Low-ZnO. For the entire experiment (d 0 to 42), pigs fed Low-ZnO or High-ZnO had reduced (P < 0.0001) ADG compared those fed the negative control. A significant treatment ×day interaction (P = 0.04) was observed for fecal Zn concentrations, where the level of Zn excreted in the feces was dependent on the sampling day in pigs fed a low level of ZnO or low level of microencapsulated ZnO. There was no evidence (P > 0.05) that small intestinal morphology differed significantly between treatments. In summary, feeding a microencapsulated form of ZnO did not alter piglet growth performance during the treatment period. Pigs fed a low level of ZnO or microencapsulated ZnO had reduced fecal Zn excretion by the end of the feeding period, but no significant impacts were observed on piglet small intestinal morphology.