Biotin: Tiny Quantities/Big Responsibilities

Compared to most vitamins, the discovery of biotin took a lot of time: 42 years between discovery and eventual synthesis in 1943. Early studies showed that animals (dogs, cats, humans) suffered a deficiency syndrome involving hair loss and skin lesions, termed “egg white injury” when consuming a diet containing large amounts of raw egg whites. Years later, other researchers determined that cooking destroyed the “egg white injury” factor, later determined to be avidin: a specific binder or antimetabolite of vitamin H (German for skin (Haut) or hair (Haar), a new water-soluble vitamin. Hungarian biochemist Paul György, who earlier had characterized and named B2 (riboflavin) and B6; determined that Vitamin H was unique and next in line, so biotin became B7 or Vitamin H.

Like many B vitamins, biotin functions as a coenzyme in carbohydrate, fat, and protein metabolism. Deficiency symptoms can include general dermatitis, skin lesions, and poor growth rate. More specific symptoms such as fatty liver and kidney syndrome (FLKS) were characterized much later by poultryresearchers, and other deficiency symptoms such as poor feathering and foot pad lesions have been noted. In pigs, colonic bacteria can synthesize biotin to an extent, so that supplemental biotin requirements were thought to be zero or very low. However, similar to current poultry understanding, general deficiency signs such as poor reproduction or reduced growth rate were observed, especially with diets containing rancid fat.

Ruminants consuming high forage rations produce much more biotin in the rumen (see graph below), but when switched to higher grain diets (such as in high producing dairy cows or feedlot beef cattle), synthesis of biotin drops off dramatically. Supplementing 20 mg biotin per head per day in modern dairy production has been noted in two large meta-analyses to improve hoof integrity and support improved milk production. Interestingly, the milk response after biotin supplementation occurs immediately after supplementing biotin; not as a result of improved lameness, but a direct biochemical change. Perhaps this indicates a relationship with lower forage and/or high corn silage diets commonly used in North America.