Chestnut Wood Tannins in Broiler Diets: Pharmacokinetics, Serum Levels during Rearing, and Intestinal Absorption Pattern of Gallic Acid

Studies on the bioavailability, serum levels, and absorption of hydrolyzable tannin compounds are lacking. In this study, we performed a pharmacokinetic trial, measured the serum levels of compounds in broilers that were reared with different feed added or not with tannins, and tested the digestibility of tannins throughout the intestinal tract. Only gallic acid and 4-O-methyl gallic acid were found in the serum. Moreover, gallic acid showed a 41.8% absolute oral bioavailability and a 72.3% relative bioavailability of gallic acid from chestnut extract compared to the standard. The rapid metabolization caused alternating serum levels during the day and night. These patterns were not affected by the feed type or the previous addition of tannins in the feed. The absorption and metabolization in the intestines occurred gradually throughout the intestinal tract. The latter was true for gallic acid as well as ellagic acid, which was not found in the serum. We can conclude that components from chestnut tannins are absorbed throughout all components of the intestinal tract and are eliminated quickly with little interaction from the feed and previous addition of tannins. Moreover, ellagic acid seems to be absorbed but would remain accumulated in the intestinal tissue or be metabolized by the microbiome.

Effects of chestnut tannins on intestinal morphology, barrier function, pro-inflammatory cytokine expression, microflora and antioxidant capacity in heat-stressed broilers

A study was conducted to evaluate the effects of chestnut tannins (CT) on intestinal morphology, barrier function, pro-inflammatory cytokine expression, microflora and antioxidant capacity in heat-stressed broilers. Four hundred 28-day-old male Ross 308 broilers were randomly assigned into four groups, with 10 replicates per group and 10 broilers per replicate. The broilers in the normal (NOR) group were kept at 22 ± 1°C and fed the basal diet, and each of the other three groups were treated with cyclic heat (33 ± 1°C from 0800 to 1800 and 22 ± 1°C from 1800 to 0800) and fed the basal diet with 0 (HT), 1 (CT1) or 2 (CT2) g of CT/kg of diet. The experiment lasted for 14 days. Compared with the HT group, broilers in the NOR and CT2 groups had higher (p < .05) average daily gain and villus height in the jejunum and lower serum d-lactate (p < .001) and diamine oxidase (p < .01) levels. The addition of 2 g CT/kg of diet increased the total antioxidant capacity (p < .001) and superoxide dismutase activities (p < .05) and zonula occludens-1 mRNA expression level (p < .05) and decreased the malondialdehyde concentration (p < .01) and mRNA expression levels of interleukin-6 (p < .001) and nuclear factor kappa B (p < .001) in the jejunal mucosa of heat-stressed broilers. The populations of Escherichia coli and Clostridium in the jejunum (p < .01) and caecum (p < .05) of broilers in the HT group were higher than those in the NOR and CT2 groups. In conclusion, the addition of 2 g CT/kg of diet seemed to be a feasible means of alleviating the negative effects of heat stress on the growth performance and intestinal function of broilers.