Biotin

Commercial D-biotin has no specific unit of activity. Thus, 1 g of D-biotin equals 1 g of activity. Pelleting or heat has little effect on biotin activity in feeds, but oxidative rancidity severely reduces biotin bioavailability. Much of the biotin in feed ingredients exists in a bound form, e-N-biotinyl-L-lysine (biocytin), which is a component of protein. Crystalline biotin is absorbed well from the small intestine, but the bioavailability of biotin in biocytin varies widely and is dependent on the digestibility of the proteins in which it is found.[1'2] Avidin, a glycoprotein found in egg albumen, binds biotin and makes it totally unavailable. Proper heat treatment of egg white will denature avidin and prevent it from binding biotin. Based on bioassay results using biotin-depleted chicks, it is apparent that among the cereal grains, bioavailability of biotin in corn is high (100%), whereas that in wheat, barley, and sorghum is about 50%.[2] Buenostro and Kratzer[3] estimated that biotin is 100% available in soybean meal and 86% available in meat-and-bone meal for laying hens.

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