Gastrointestinal health evaluation through amplicon-based metagenomics, histopathology and morphometry in finishing pigs fed an olive mill wastewater polyphenol extract

Pig microbiota influences overall animal health, and changes to the diet can modify gut microbiota composition and animal growth rate, bringing about environmental and economic advantages. Dietary polyphenols, due to their antimicrobial and antioxidant properties, may improve gut health. However, their use in monogastric diets is still emerging. The present study investigated the effects of polyphenols derived from an olive mill wastewater (OMWW) extract on gastrointestinal histopathology and morphometry and intestinal microbiota composition. One hundred thirty-five female Landrace × Duroc finishing pigs were randomly allocated to three experimental groups fed: a control (C) diet, or C diet supplemented with 74 ppm (P-LOW) or 225 ppm of OMWW polyphenols (P-HIGH). The experiment lasted 85 days, after which 15 animals per group were slaughtered. Final body weight was 148.1 ± 4.6 kg. The morphological analysis of the intestine demonstrated a significant increase in the villus height:crypt depth (VH/CD) ratio in the ileum of pigs from P-LOW and P-HIGH groups and the jejunum of pigs from P-HIGH group vs C. 16S amplicon sequencing analysis showed an increase in two indexes of alpha diversity in the caecum of pigs from P-HIGH vs P-LOW. Differential abundance analysis showed that pigs from P-HIGH had a greater abundance of beneficial bacteria, especially Eubacterium and Treponema, and fewer harmful ones, including Fusobacterium, Bacteroides helcogenes, and Corynebacterium urealiticum. The results suggest that OMWW polyphenols may positively influence the pig gut microbiota and overall intestinal health. Further studies are needed to confirm these data.