Donor age and body weight determine the effects of fecal microbiota transplantation on growth performance, and fecal microbiota development in recipient pigs

Background: The application of fecal microbiota transplantation(FMT) to improve swine growth performance has been sporadically studied. Most of these studies used a single microbiota source and thus the effect of donor characteristics on recipient pigs' fecal microbiota development and growth performance is largely unknown.Results: In this study, we collected feces from six donors with heavy(H) or light(L) body weight and different ages(d 42, nursery; d 96, growing; and d 170, finisher) to evaluate their effects on the growth performance and fecal microbiota development of recipient pigs. Generally, recipients that received two doses of FMT from nursery and finisher stages donor at weaning(21 ± 2 days of age) inherited the donor's growth pattern, while the pigs gavaged with grower stage material exerted a numerically greater weight gain than the control pigs regardless of donor BW.FMT from heavier donors(NH, GH, and FH) led to the recipients to have numerically increased growth compared to their lighter counterparts(NL, GL, and FL, respectively) throughout the growing and most finishing stages. This benefit could be attributed to the enrichment of ASV25 Faecalibacterium, ASV61 Faecalibacterium, ASV438Coriobacteriaceae＿unclassified, ASV144 Bulleidia, and ASV129 Oribacterium and decrease of ASV13 Escherichia during nursery stage. Fecal microbiota transplantation from growing and finishing donors influenced the microbial community significantly in recipient pigs during the nursery stage. FMT of older donors' gut microbiota expedited recipients' microbiota maturity on d 35 and 49, indicated by increased estimated microbiota ages. The ageassociated bacterial taxa included ASV206 Ruminococcaceae, ASV211 Butyrivibrio, ASV416 Bacteroides, ASV2Streptococcus, and ASV291 Veillonellaceae. The body weight differences between GL and GH pigs on d 104 were associated with the increased synthesis of the essential amino acid, lysine and methionine, mixed acid fermentation, expedited glycolysis, and sucrose/galactose degradation.Conclusions: Overall, our study provided insights into how donor age and body weight affect FMT outcomes regarding growth performance, microbiota community shifts, and lower GI tract metabolic potentials. This study also provided guidance to select qualified donors for future fecal microbiota transplantation.