Nutritionists have two main strategies available to prevent enterotoxigenic Escherichia coli growth in the intestine: either using an antimicrobial approach, which tends to delay microbiota maturation to later stages (e.g.: ZnO is used as an effective method to prevent post-weaning diarrhea), or designing diets to promote and modulate the establishment of commensal microbiota in the intestinal tract immediately after weaning (e.g.: fiber helps to maintain enteric health by lowering protein fermentation and promoting the proliferation of commensal microbiota). Both these strategies appear to be contradictory in the mode of action and are difficult to combine in a comprehensive way. However, in practice, they are frequently used together, although there is little information on the formulation of starter diets containing medicines. It would be of particular interest to know about the possible influence of dietary composition on the activity of pharmacological doses of ZnO in the diet. For these reasons, the present study was designed to evaluate the effects of including wheat bran (WB) and ZnO alone or combined in the diet of early-weaning pigs on productive performance and microbial activity in the gastrointestinal tract (trial 1). A total of sixty-four piglets were distributed in a 2 x 2 factorial combination of two levels of WB (0 vs. 40 g/kg) and ZnO (0 vs. 3 g/kg) in the diet.
The inclusion of ZnO in the diet improved (P < 0.05) the feed intake and growth of the animals and reduced (P < 0.05) the incidence of diarrhoea. The inclusion of WB increased (P < 0.001) short-chain fatty acid concentrations and decreased (P < 0.05) E. coli K88 counts. However, simultaneous incorporation of WB and ZnO increased (P < 0.05) E. coli counts. Two in vitro trials were also designed to clarify hypotheses derived from the in vivo test: (1) the ability of WB and other fibre sources to bind E. coli in vitro (trial 2) and (2) the in vitro interactions between WB and ZnO with respect to E. coli growth (trial 3).
Based on the results of the present study, we conclude that the incorporation of WB in the diet of early-weaning piglets may improve their gut health by modulating the activity of the intestinal microbiota, enhancing the fermentation and blocking the attachment of E. coli K88 to the intestinal mucosa. A negative interaction observed in vivo and in vitro between WB (rich in phytate) and ZnO raises the interest of considering the inclusion of phytase enzymes to reduce the therapeutic levels of ZnO in post-weaning diets.
F Molist, RG Hermes, A Gómez de Segura, SM Martín-Orúe, J Gasa, EG Manzanilla and JF Pérez, 2011. British Journal of Nutrition, 105: 1592?1600.