Effect of Saccharomyces cerevisiae Postbiotics and Essential Oil on Growth Performance and Intestinal Health of Weanling Pigs during K88 ETEC Infection.

Enterotoxigenic E. coli (ETEC) is one of the major bacterial infections, causing substantial economic losses globally in the swine industry. This study aimed to investigate the impact of low Saccharomyces cerevisiae fermentation postbiotics (SCFP), high SCFP, essential oil (EO), or their combination on the growth performance and health of weanling pigs during ETEC infection. Forty-eight male weanling pigs were randomly allocated to 5 groups: 1) control group (CON - basal diet, n=16); 2) low SCFP group (LSC - basal diet + 1.25 g/kg SCFP, n=8); 3) high SCFP group (HSC - basal diet + 2 g/kg SCFP, n= 8); 4) EO group (EO -basal diet + 0.4 g/kg EO, n=8); 5) the combination group (SE - basal diet + 1.25 g/kg SCFP + 0.4 g/kg EO, n=8). On day 15 of the trial, pigs in CON were divided into positive control (PC) and negative control (NC), and all pigs, except in NC, were challenged with ETEC. Under the normal condition, dietary LSC, HSC, EO and EO all increased ADG (P< 0.05), and decreased F:G ratio (P< 0.05) accompanied by decreased MDA and increases in CAT, T-SOD, T-AOC indicating enhanced anti-oxidative capacity as well as decreased IL-2, IL-8, INF-γ indicating mitigated systemic inflammation. During ETEC infection, all treatments alleviated ETEC-induced ADG reduction, diarrhea, damages in intestinal permeability and morphology, and down-regulation of tight junctions (Claudin1, ZO-1 and Occludin), while HSC and EO exhibited additional protections. All treatments increased CAT, T-SOD, T-AOC and decreased MDA in serum and jejunal mucosa at similar degrees (P< 0.05). Moreover, all treatments alleviated ETEC-induced inflammation as shown by decreased IL-6, TNF-α, INF-γ, and increased IL-4 and IL-10 in serum or jejunal mucosa (P< 0.05), and enhanced the immunity by increased serum IgG and mucosal sIgA (P< 0.05). HSC and SE further reduced mucosal INF-γ and TNF-α than LSC or EO aligning with their additional protection against diarrhea during ETEC infection. Additionally, the key gut bacteria (e.g. Terrisporobacter) related to the benefits of SCFP and EO were identified. In sum, all treatments enhanced growth performance and protected against ETEC-induced intestinal damages through the regulation of redox and immune homeostasis. HSP and SE offered extra protection during disease for their additional control of inflammation. Our study provided new insight into the use of feed additives in the context of animal health states.