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Utilization of Dietary Vitamin B₁₂ and Cobalt by Mature Horses^{1, 2,}

Theracon, Inc., Topeka, Kansas 66601

Abstract

RELATIVELY little is known about the role of vitamin B₁₂ and cobalt in the nutrition of the equine. However, many horses in training in the United States receive daily injections of 10,000 to 20,000 µg of vitamin B₁₂ in addition to a regular dietary source of vitamin. The National Research Council (1966) does not make a recommendation for a dietary allowance of vitamin B₁₂. Alexander and Davies (1969) noted that horses consuming a natural diet had vitamin B₁₂ serum levels higher than the rat and man, similar to sheep, and lower than the rabbit.

Nonruminants such as rats and pigs need a dietary source of vitamin B₁₂; whereas, rumen bacteria are capable of synthesizing adequate vitamin B₁₂ for their host, provided adequate cobalt and phosphorus are present in the diet (Lewis, 1961). Dairy cattle have been shown to excrete 50 times more vitamin B₁₂ than they consumed (Teeri et al., 1955) and rumen bacteria in the sheep synthesized a greater amount of vitamin B₁₂ when consuming natural foodstuffs than when consuming semi-purified diets (Barnett and Reid, 1961).

¹ Financial support provided by the American Quarter Horse Association through the Morris Animal Foundation, Denver, Colorado.

² The authors wish to acknowledge the assistance of E. I. Shaw, Radiation Biophysics, University of Kansas, for analysis of ⁶⁰Co-labeled B₁₂ activity.