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The Fecal and Urinary Excretion of Certain B Vitamins by Sheep Fed Hay and Semi-Synthetic Rations¹

U. S. Department of Agriculture

Abstract

The apparent synthesis of riboflavin as measured by urinary and fecal excretion by sheep was not essentially affected by feeding a low-protein ration or by adding urea to the ration. Feeding a low-protein ration to sheep reduced the urinary excretion of niacin to about one-third of the amount excreted by sheep fed a ration containing 12.6 percent protein. This is probably due to the lower intake of tryptophan which can be converted to niacin by sheep. The total excretion of pantothenic acid exceeded by four to 6-fold the amount ingested when semi-synthetic rations were fed. Sheep fed a semi-synthetic ration adequate in protein excreted over 93 percent of the pantothenic acid in the urine and less than 7 percent in the feces. Sheep fed a low-protein ration excreted in the urine significantly less pantothenic acid than sheep fed a ration adequate in protein.

Relatively large amounts of vitamin B₁₂ are synthesized in the gastrointestinal tract of sheep. The ratio of B₁₂ ingested to the amount excreted in the feces by the sheep fed the semi-synthetic rations was in the order of 120 to 210. The microbial synthesis of B₁₂ when a mixed hay ration was fed exceeded by about three times the synthesis when a semi-synthetic ration was fed. Approximately 99 percent of the excreted B₁₂ was found in the feces.

¹ Bureau of Animal Industry, Beltsville, Maryland.