The objective of this study was to investigate effects of zinc glycinate (ZnGly) supplementation reducing zinc oxide (ZnO) in feeds on intestinal health and growth of nursery pigs challenged with F18+Escherichia coli (E. coli). In total, 72 nursery pigs (BW 6.5 ± 0.5 kg) were allotted in a randomized complete block design to nine treatments: (1) NC: no challenge/no supplement; (2) PC: E. coli challenge/no-supplement; (3) E. coli challenge/ZnO at 2,500 mg/kg; (4, 5, and 6) E. coli challenge/ZnGly at 400, 800, and 1,200 mg/kg; and (7, 8, and 9) E. coli challenge/ZnGly at 400 mg/kg and ZnO at 700, 1,400, and 2,357 mg/kg. Pigs were fed for 28 d based on two phases (phase 1: 14 d and phase 2: 14 d). On day 7, challenged groups were orally inoculated with F18+E. coli at 6 × 109 CFU/mL whereas NC received saline solution. The PC showed reduced ADG (P = 0.076) and G:F (P = 0.055) during phase 1 and increased fecal score (P < 0.05) during the first week of postchallenge when compared with NC, whereas supplementation of ZnGly from 0 to 1,200 mg/kg linearly increased (P = 0.092) G:F and decreased (P < 0.05) the fecal score of the pigs challenged with F18+E. coli. Supplementation of ZnGly from 0 to 1,200 mg/kg had quadratic effects on TNF-α (P = 0.065; minimum 1.13 pg/mg at 850 mg/kg ZnGly), IL-8 (P = 0.093; minimum 0.53 ng/mg at 494 mg/kg), and protein carbonyl (P = 0.054; minimum 2.30 pg/mg at 675 mg/kg) and linearly increased mRNA expressions of ZIP4 (P = 0.057) and ZnT5 (P = 0.075) in the jejunum of the pigs. Supplementation of ZnGly from 0 to 1,200 mg/kg linearly increased (P < 0.05) the relative abundance of Actinobacteria and had quadratic effects on Cyanobacteria (minimum 0.67% at 625 mg/kg ZnO) and Proteobacteria (maximum 45.6 g/d at 735 mg/kg) at the phylum level, with linearly decreased (P < 0.05) Enterobacteriaceae at the family level in the jejunal mucosa-associated microbiota of the pigs. There was no difference in growth performance during the overall period, although pigs fed with ZnO at 2,500 mg/kg had greater (P < 0.05) ADG than pigs fed with ZnGly at 400 mg/kg during the first week of the post challenge period. In conclusion, ZnGly could be an alternative to the pharmaceutical use of ZnO without negatively affecting the growth of nursery pigs by enhancing intestinal Zn absorption, reducing intestinal inflammation and oxidative stress, and providing positive changes in jejunal mucosa-associated microbiota.
Keywords: Escherichia coli; intestinal health; nursery pigs; zinc glycinate; zinc oxide.
Enterotoxigenic Escherichia coli (E. coli) strains such as F18+ and F4+E. coli are prominent harmful bacteria that cause impaired intestinal health to nursery pigs with postweaning diarrhea, leading to significant economic losses in the swine industry. In previous years, swine producers used excessively high levels of zinc oxide (ZnO) in feeds for therapeutic purpose as a growth promoter with diarrhea prevention. However, the pharmaceutical use of ZnO is prohibited by the legislation of several countries due to potential health and environmental concerns. Considering the biological functions of zinc (Zn) and the biological efficacy of the organic mineral, zinc glycinate (ZnGly) could effectively enhance the intestinal health of nursery pigs, leading to a decrease in the use of ZnO in feeds. This study aimed to investigate the effects of ZnGly supplementation, allowing the reduced use of ZnO for growth performance and intestinal health of nursery pigs challenged with F18+E. coli. Supplementation of ZnGly at a range of 400 to 675 mg/kg would reduce the negative impacts of F18+E. coli by reducing intestinal inflammation and oxidative stress with positive changes in jejunal microbiota, leading to improved growth performance and reduced diarrhea. In particular, ZnGly supplementation at 400 mg/kg could effectively reduce the use of ZnO in nursery feeds by having similar effects to the pharmaceutical use of ZnO.
© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.