Effects of dietary protein level and zinc oxide supplementation on the incidence of post-weaning diarrhoea in weaner pigs challenged with an enterotoxigenic strain of Escherichia coli

The interactive effects of dietary protein level, zinc oxide (ZnO) supplementation and experimental infection with enterotoxigenic E. coli (ETEC) on the incidence of post-weaning diarrhoea (PWD) and indices of protein fermentation were examined. Ninety-six, individually housed 21-day-old pigs were used in a split plot experiment, with the whole plot being challenge or no challenge with ETEC and the dietary treatments used as subplots and arranged in a completely randomised 2×2 factorial design, with the factors being (i) 2 dietary protein levels [251g/kg (high) vs. 192g/kg (low) crude protein] and (ii) addition or no addition of 2500ppm ZnO. Between days 1 and 14 after weaning, ETEC infection increased faecal consistency (FC; looser faeces) but only in pigs fed the high protein diet (P<0.05) or without ZnO (P<0.1). Pigs fed a high protein diet without ZnO showed more loose faeces (higher FC) compared to pigs fed either a high protein diet with ZnO supplementation or pigs fed lower protein diets without and with ZnO supplementation (P<0.05). Feeding either a low protein diet or ZnO decreased (P<0.05) PWD. Feeding a low protein diet decreased (P<0.001) plasma urea nitrogen (PUN) and faecal NH₃-N contents. There were no 2- or 3-way interactions (P>0.05) between the independent variables for PWD, PUN and faecal NH₃-N. The results indicate that feeding a low protein diet supplemented with amino acids or adding ZnO to either low or high protein diets could be used as dietary strategies to reduce PWD in piglets.