Introduction
Biotin is a β-vitamin involved with carbohydrate metabolism, propionate production and metabolism, fatty acid synthesis, cellulose digestion, and keratin production. Rumen microorganisms and normal feed stuffs usually provide adequate biotin to prevent deficiency signs from occurring in cattle. Today's dairy cows are expected to produce copious amounts of milk, which could ultimately be placing the cow under additional stress. This additional stress could reduce the amount of biotin that can be produced by rumen microorganisms or increase the cow's requirement for biotin. Dermatitis, dry scaly skin, and hair loss are clinical signs of a biotin deficiency.
Previous research with swine has shown that supplemental biotin can improve hoof horn development. The dairy industry has recently begun to investigate supplementing biotin to lactating dairy cows. Midla et al. (1998) and Bergsten et al. (1999) reported that 20 mg/day of supplemental biotin reduced hoof lesions in dairy cattle. Besides improving hoof quality, biotin supplementation (20 mg/day) also increased milk production (305 day mature equivalent) by 310 kg (Midla et al., 1998) and 878 kg (Bergsten et al., 1999) in those two field studies. Field trials lack the controlled atmosphere needed to determine a cause and effect relationship. The increase in milk production found when biotin was supplemented in field trials could possibly be a result of increased dry matter intake (DMI) because of improved hoof health. Healthy cows generally are more willing to stand and eat than are lame cows, and this factor alone could increase milk production. Controlled studies allow for important measurements, such as DMI and blood metabolites, to be measured at regular intervals. These blood metabolites could be used to possibly explain the mode of action that causes an increase in milk production from biotin supplementation. This study focused on determining the effects of biotin supplementation on feed intake, milk production, milk composition, and glucose metabolism when fed to lactating Holstein cows.