This study aimed to evaluate the effect of hydrolysable tannin supplementation on morphology, cell proliferation and apoptosis in the intestine and liver of fattening boars. A total of 24 boars (Landrace × Large white) were assigned to four treatment groups: Control (fed commercial feed mixture) and three experimental groups fed the same diet supplemented with 1%, 2% and 3% of hydrolysable tannin-rich extract. Animals were housed individually with ad libitum access to feed and then slaughtered at 193 d of age and 122 ± 10 kg body weight. Diets supplemented with hydrolysable tannin affected the morphometric traits of the duodenum mucosa as reflected in increased villus height, villus perimeter and mucosal thickness. No effect was observed on other parts of the small intestine. In the large intestine, tannin supplementation reduced mitosis (in the caecum and descending colon) and apoptosis (in the caecum, ascending and descending colon). No detrimental effect of tannin supplementation on liver tissue was observed. The present findings suggest that supplementing boars with hydrolysable tannins at concentrations tested in this experiment has no unfavourable effects on intestinal morphology. On the contrary, it may alter cell debris production in the large intestine and thus reduce intestinal skatole production.

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Abandoning traditional practice of piglet castration will impact the pigmeat sector. As a consequence, there is a need for research aiming at reducing boar taint caused by androstenone and skatole. Skatole is metabolized by cytochrome P450 enzymes (CYP450) in the liver. Skatole hepatic clearance is believed to be hindered by androstenone. Diet ingredients may modify skatole metabolism. Therefore, we tested the effect of hydrolysable tannins. We fed 51 young boars with 1-3 % chestnut wood extract as supplementary diet. After slaughter, the tissues were collected to assess androstenone and skatole accumulation in fat and to measure CYP450 activities, gene, and protein expression in the liver and intestine. Protein expression of two enzymes involved in androstenone metabolism, 3-beta-hydroxysteroid dehydrogenase (3β-HSD) and sulfotransferase family 2A member 1 (SULT2A1), was assessed, and feces collected to evaluate skatole production. Results show that intestinal skatole production in boars supplemented with 3 % of chestnut wood extract was more than halved. The intestinal catalytic activities of CYP450 were tenfold lower than hepatic and were mainly unaffected by tannins. Findings indicate a potential effect of tannins on steroidogenesis, which in the absence of effect on 3β-HSD and SULT2A1 expression suggests lower synthesis of androstenone due to tannins.