Biotin studies in pigs. 5. The post-ileal absorption of biotin

Six pigs were given a biotin-deficient diet (10 micrograms biotin/kg) for 14 weeks. The pigs were given the same diet for a further 42 d with one of three biotin treatments: no supplement, 400 micrograms biotin/d given orally, 400 micrograms biotin/d infused into the caecum. The concentrations of biotin in the liver, kidney and heart, at the conclusion of 42 d were greater in the pigs given the oral biotin supplement than in the unsupplemented pigs. The values for the pigs given the caecal infusion of biotin were intermediate. The excretion of biotin in faeces was increased from 35 to 101 micrograms/d by the caecal biotin infusion, and the urinary excretion was increased from 35 to 83 micrograms/d. The oral dose of biotin increased urinary biotin excretion from 35 to 345 micrograms/d, but there was no change in faecal biotin excretion. Two pigs were fitted with ileal cannulas and catheters in the vena cava. The pigs were given a dose of [14C] biotin either into the caecum, when the ileum was occluded by a bladder catheter, or orally. [14C] biotin was measured in the urine and plasma and showed that post-ileal biotin absorption was 8% as efficient as the absorption of biotin after oral dosing.