The Horse
An excerpt that answers your question:
<BLOCKQUOTE class=“ip-ubbcode-quote”><font size="-1">quote:</font><HR> Mind you, there’s still much we don’t understand. For instance, we’re still not entirely sure why biotin should need to be supplemented in horses at all. Many feeds, particularly growing forage plants (pasture), have what appears to be a more-than-adequate biotin content. On top of that, the helpful fiber-digesting bacteria in the equine cecum seem to manufacture enough B vitamins for all of a horse’s daily needs as part of their normal metabolism. There is some question as to how much of those B vitamins are absorbed by the horse; they are created in the large intestine, while the primary site of absorption of vitamins is back in the small intestine. Equine digestive systems being one-way, the nutrients generated by the gut microflora might pass through the horse’s system largely unused. No one is yet sure how much might be utilized.
Regardless, true biotin deficiencies have never been documented in horses except when they’ve been artificially induced (and that takes some doing). Feeding biotin at a level that has an impact on hoof growth is not really a matter of correcting a deficiency; it’s considerably over and above that. In essence, it’s taking a nutrient and feeding it at a level beyond normal requirements, at which it really becomes a therapeutic medication (the technical term is hyperalimentation). Fortunately, biotin, like all B vitamins, is water soluble, which means it is not stored in the horse’s tissues. The body uses what it needs on a daily basis, and excretes any extra in the urine. That means there’s very little chance of a horse developing a biotin toxicity, even when fed amounts many times greater than he needs for maintenance metabolism.
Why do some horses seem to need more than the maintenance amount of biotin? The jury’s still out on that question. It might be because those horses don’t absorb or utilize biotin as well as other horses, or they might simply have a higher requirement than horses with naturally good-quality hoof horn. But the fact remains that some horses with poor-quality hooves appear to respond positively to biotin supplementation. Not all do–and what separates the horses which respond from those which don’t is another mystery.
It’s worth noting, too, that there’s still a considerable amount of controversy over what constitutes the “optimum” level of biotin for good hoof growth. Because of its high safety margin, many supplement manufacturers have taken the “if some is good, more is better” approach. The truth is that no one really knows the best dosage. The best guess we have at this point is that horses might be able to utilize about 15 to 20 mg of full-activity biotin per day
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). I feed a teaspoonful daily in addition to BP and other supplements.
