The digestibility of biotin in protein supplements and cereal grains for growing pigs

Studies were carried out with six growing barrows fitted with a simple T-cannula 5 to 10 cm anterior to the ileo-cecal sphincter. In Exp. 1, the digestibility of biotin was determined in three cornstarch-based diets formulated to contain 16% CP by supplementation with soybean meal (SBM), meat and bone meal (MBM) and canola meal (CM). In Exp. 2 the digestibility of biotin was determined in three diets that contained 96.8% barley, corn or wheat. Experiments 1 and 2 were conducted according to a replicated 3 X 3 latin square design. In Exp. 3 pigs were fed a cornstarch-based diet supplemented with 12% vitamin-free casein to determine the amount of endogenous biotin. In Exp. 4 the digestibility of supplemental biotin was determined. There was a small amount of endogenous biotin in ileal digesta, 11 micrograms/kg DMI. Digestibilities of biotin determined at the distal ileum (apparent digestibilities corrected for endogenous biotin) were 55.4, 2.7 and 3.9% in SBM, MBM and CM, respectively, and 4.8, 4.0 and 21.6% in barley, corn and wheat, respectively. The digestibility of supplemental biotin was 93.5%. There was a large increase in the level of biotin between digesta collected from the distal ileum and in feces, ranging from 138 to 324 micrograms/kg DMI. With the exception of the CM diet, this increase exceeded dietary biotin intake. Biotin in many feedstuffs was not available in the small intestine.