A Comparison of Diets Supplemented with a Feed Additive Containing Organic Acids, Cinnamaldehyde and a Permeabilizing Complex, or Zinc Oxide, on Post-Weaning Diarrhoea, Selected Bacterial Populations, Blood Measures and Performance in Weaned Pigs Experimentally Infected with Enterotoxigenic E. coli †

SIMPLE SUMMARY: This experiment was conducted to assess the effects of three diets on diarrhoea, performance (weight change, feed intake and feed conversion ratio), selected bacterial populations and blood measures of weaner pigs infected with enterotoxigenic E. coli. The three diets were: base diet (no antimicrobial compounds), base diet containing zinc oxide, and base diet containing a feed additive (blend of organic acids, cinnamaldehyde and permeabilizing complex). Only feeding zinc oxide decreased diarrhoea, with zinc oxide-fed pigs performing better than base diet-fed pigs. Zinc oxide-fed pigs performed similarly to pigs fed the organic acids, cinnamaldehyde and permeabilizing complex. Significant interactions between treatment and day after weaning were found for some bacterial populations, although the implications of such findings require further examination. ABSTRACT: The effects of feeding a diet supplemented with zinc oxide (ZnO) or a blend of organic acids, cinnamaldehyde and a permeabilizing complex (OACP) on post-weaning diarrhoea (PWD) and performance in pigs infected with enterotoxigenic E. coli (ETEC) were examined. Additionally, changes in selected bacterial populations and blood measures were assessed. A total of 72 pigs weaned at 22 d of age and weighing 7.2 ± 1.02 kg (mean ± SEM) was used. Treatments were: base diet (no antimicrobial compounds); base diet + 3 g ZnO/kg; base diet + 1.5 g OACP/kg. Dietary treatments started on the day of weaning and were fed ad libitum for 3 weeks. All pigs were infected with an F4 ETEC on d 4, 5 and 6 after weaning. The incidence of PWD was lower in pigs fed ZnO (p = 0.026). Overall, pigs fed ZnO grew faster (p = 0.013) and ate more (p = 0.004) than the base diet-fed pigs, with OACP-fed pigs performing the same (p > 0.05) as both the ZnO- and base diet-fed pigs. Feed conversion ratio was similar for all diets (p > 0.05). The percentage of E. coli with F4 fimbriae was affected a day by treatment interaction (p = 0.037), with more E. coli with F4 fimbriae found in pigs fed ZnO on d 11 (p = 0.011) compared to base diet-fed pigs. Only significant time effects (p < 0.05) occurred for blood measures. Under the conditions of this study, inclusion of OACP gave statistically similar production responses to pigs fed ZnO, however pigs fed ZnO had less PWD compared to OACP- and the base diet-fed pigs.