Valorisation of Agri-Food By-Products as Dietary Interventions to Support Gut Microbiota and Health in Weaned Pigs

Weaning is the most stressful period in the life of the pig, which can be associated with a reduction in growth performance, perturbations to the gut microbiome and an increase in gastrointestinal disease (1) . In the absence of prophylactic antibiotics, therapeutic levels of zinc oxide (ZnO) have been offered in feed for two weeks, to support the young animal through this transition. However, due to both environmental and antimicrobial resistance concerns, the use of ZnO was banned in the UK and EU from June 2022 (2) . Agri-food by-products (AFBPs) hold interest as potential alternatives to ZnO due to the range of bio-active compounds they contain. For example, polyphenols found in fruit and vegetable pulps and peelings display anti- inflammatory, antimicrobial and antioxidant properties (3) . The aim of the current study was to determine the potential of different fruit and vegetable-derived AFBP to impact gut microbiota composition as indicator of gut health. This trial was performed at the University of Leeds National Pig Centre with approval from the University’s animal welfare and ethical review body. AFBPs were obtained from a variety of fruit and vegetable sources and formulated into weaner pig feed. A total of 320 pigs were weaned onto this trial and randomly assigned to one of eight diets (A-H) for a 14-day period post-weaning. Diet A was a negative control with no additional additive, diet B contained therapeutic levels of ZnO (3100 ppm) as a positive control and diets C-H each contained different AFBP streams. Pigs were housed in groups of 5, with 8 replicate pens per treatment. After 14 days, digesta samples were collected from 10 pigs per treatment from the jejunum, ileum and caecum to identify changes in the gut microbial community. From the extracted DNA, the V4 region (16s rRNA gene) was sequenced. Amplicons were cleaned and aligned to the SILVA database (v132) in Mothur with statistical analysis performed in R. Whilst no differences in α-diversity (Chao1, Shannon, Simpson; P>0.05) were observed, a difference in community composition was identified in both the ileum (p=0.008) and caecum (p=0.002). ZnO showed significant differences in β-diversity (NMDS, Bray-Curtis distances) to the negative control and some of the AFBP groups, whilst others were similar. The ZnO diet showed enhanced suppression of both Escherichia-shigella and Campylobacter in both the ileum and the caecum compared with the negative control. AFBP groups varied in their effectiveness, and this varied with gut location. With refinement of the dosage and a potential blend of additives to maximise effectiveness across a range of gut health and performance parameters, there is scope to include AFBPs in the diet of the weaned pig to support gut health and reduce the susceptibility of the microbiome to pathogen colonisation.