Evaluating the influence of tannic acid alone or with polyethylene glycol on the intestinal absorption capacity of broiler chickens, using d-xylose absorption test

Dietary tannins hinder the growth performance of broiler chickens by reducing the digestion and/or absorption of dietary ingredients. An experiment was conducted on thirty 28-day-old broiler chickens, in 3 groups of 10 birds, in order to evaluate the influence of tannic acid (TA) alone or with polyethylene glycol (PEG) on the absorption function of intestinal epithelium, using d-xylose absorption test. The experimental groups received d-xylose solution alone (500 mg/kg BW, group 1), with TA (2 g/bird, group 2), or with TA and PEG (2 and 1 g/bird, respectively, group 3) by oral gavage. This was followed by the blood sampling from the birds on 30 min interval basis, for 3 h. The results showed that the level of plasma d-xylose in all three groups showed quadratic correlations with time. The level of plasma d-xylose of group one reached to its peak at 60–90 min after the ingestion of d-xylose solution (P<0.001, r2 = 0.89). However, the group of birds that received d-xylose with TA, had lower plasma d-xylose levels, with no apparent peak (P<0.01, r2 = 0.79). The group of birds that received TA with PEG had a similar quadratic correlation of plasma d-xylose with group one (P<0.001, r2 = 0.91). It was concluded that TA reduces the absorption of d-xylose highly likely by distracting the trans-cellular and/or para-cellular mechanisms responsible for the transport of the pentose sugar across the intestinal wall. However, the ingested PEG, by the formation of effective complexes with TA, enhances the transport of d-xylose across the intestine.