SYNTHESIS AND ABSORPTION OF BIOTIN IN THE LARGE-INTESTINE OF PIGS

Six gilts, with an average initial weight of -70 kg, were fitted with a simple T-cannula 5-10 cm anterior to the ileo-caecal sphincter. Starch was infused continuously through the cannulas to study the effect of fermentation in the large intestine on microbial biotin synthesis. In addition, the efficiency of absorption of microbial-derived biotin in the large intestine was estimated. The pigs were fed 600 g of a purified cornstarch-based diet twice daily, with soy protein as the sole source of protein and biotin. The infusion treatments were carried out in the form of a cross-over design. The net increase in the level of biotin between ileal digesta and faeces was 62.0 μg per 24 h following starch infusion, but only 24.7 μg per 24 h when water was infused. Despite the high production rate of microbial biotin in the large intestine following starch infusion, there was no increase (P > 0.05) in the level of biotin in plasma as well as in urine. It can be concluded that microbial-derived biotin has a low efficiency of absorption in the large intestine of the pig. However the apparent digestibility of biotin in soy protein, determined at the distal ileum, ranged from 36 to 40%, confirming that the small rather than the large intestine represents the main site of biotin absorption in the pig. © 1990.