Effect of supplementation of a blend of protected aromatic compounds including benzoic acid on weaned piglets’ diets as an alternative to Zinc Oxide: growth performance and faecal microbial profile.

Abstract Organic acids (OA), especially benzoic acid, have long been used for their wide antimicrobial activity and have shown to promote intestinal health and increase average daily gain (ADG), feed intake (FI) and feed conversion ratio (FCR) of pigs. On the other side, the European Commission decided to ban the use of pharmacological levels of zinc oxide (ZnO) in diets for this animal species from 2022. The aim of this study was to investigate the effect of a blend of protected aromatic compounds including benzoic acid (PBA) as a substitute of supra-nutritional levels of ZnO in piglet diets on growth performance and on gut microbiota profile. The trial was conducted in 4 farms. For each farm, piglets were allocated to one of the two experimental groups: i) piglets receiving a diet with 2.5 g/kg of ZnO; ii) piglets receiving the same diet but with 2.5 g/kg of PBA. Piglets were blocked to each diet based on body weight and sex. 1720 piglets were allocated to the ZnO treatment and 1728 to the PBA. The animals received the treatment for a total of 6 weeks starting from weaning (28 days old). Cumulative performance from weaning to 6 weeks post-weaning were calculated. Faecal pool samples were collected from 8 box replicates per group from each farm to characterize the microbial profile. Piglets receiving PBA showed higher ADG (P