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 <0.01) and lower FCR (P <0.05) in all the farms compared to ZnO, no differences in feed intake (FI)were seen. A reduction of mortality and diarrhoea incidence was observed in pigs from the PBA treatment compared to those in the ZnO (P <0.01). The faecal microbiota was characterized by a higher alpha diversity in the PBA treatment (Shannon: 4.52 vs 4.1, P <0.01; invSimpson: 36.1 vs 24.5 P <0.01). The microbial composition was significantly influenced by treatment (P <0.01, R²= 0.03). Animals receiving PBA were characterized by a higher abundance of Ruminococcus (FDR <0.01), Prevotellaceae (FDR <0.01) and Fibrobacteraceae (FDR <0.05), known for their fiber fermenting abilities. In conclusion, the supplementation with PBA positively influenced the microbial profile of weaned piglets by increasing the alpha diversity, and by favouring the proliferation of known beneficial bacteria, related to the metabolism of polysaccharides and production of SCFA. These findings on the faecal microbial profile can contribute to explain the higher ADG and lower FCR observed in piglets supplemented with PBA.

长期以来，有机酸（OA），尤其是苯甲酸因其广泛的抗菌活性而被使用，并已显示出可促进肠道健康并增加猪的平均日增重（ADG），饲料采食量（FI）和饲料转化率（FCR）。另一方面，欧盟委员会决定从2022年起禁止在这种动物的饮食中使用氧化锌（ZnO）的药理学水平。这项研究的目的是研究包括苯甲酸在内的受保护芳香化合物的混合物的作用。酸（PBA）替代仔猪日粮中营养水平超高的ZnO，可提高生长性能和肠道菌群。该试验在4个农场中进行。对于每个农场，将仔猪分配到两个实验组之一：i）接受日粮含2.5 g / kg ZnO的仔猪；ii）仔猪接受相同的饮食，但是有2个。5 g / kg的PBA。根据体重和性别，对每种饮食都禁止仔猪进食。将1720头仔猪分配给ZnO处理，将1728头仔猪分配给PBA。从断奶（28天大）开始，动物接受了总共6周的治疗。计算从断奶到断奶后6周的累积表现。从每个农场的每组8个盒重复中收集粪便池样品，以表征微生物特征。与ZnO相比，在所有猪场中接受PBA的仔猪均表现出较高的ADG（P <0.01）和较低的FCR（P <0.05），未观察到饲料采食量（FI）的差异。与ZnO相比，PBA处理的猪的死亡率和腹泻发生率均降低（P <0.01）。粪便微生物群的特点是在PBA处理中具有更高的α多样性（Shannon：4.52 vs 4.1，P <0.01；invSimpson：36.1 vs 24.5 P <0.01）。微生物组成受到治疗的显着影响（P <0.01，R² = 0.03）。接受PBA的动物具有较高的瘤胃球菌（FDR <0.01），原核科（FDR <0.01）和纤维杆菌科（FDR <0.05）丰富的特点，这些纤维以其纤维发酵能力而著称。总之，补充PBA通过增加α多样性并促进与多糖代谢和SCFA产生有关的已知有益细菌的增殖，对断奶仔猪的微生物特性产生积极影响。这些关于粪便微生物特征的发现可以解释在补充PBA的仔猪中观察到的较高的ADG和较低的FCR。