The synthesis of vitamins in the rumen of sheep. I. The effect of diet on the synthesis of thiamine, riboflavin, and nicotinic acid

Abstract

The levels of thiamine, riboflavin, and nicotinic acid in the rumen of sheep, fed a variety of diets, were determined by chemical methods. The intakes of dry matter, B vitamins, protein, non-protein nitrogen, and energy were recorded, and the rumen volumes on each diet were estimated. The diets were mainly of a semi-synthetic type, consisting of sodium hydroxide-treated straw supplemented with varying amounts of casein, urea, starch, sugar, and minerals. When the intake of the B vitamins was high, little microbial synthesis took place in the rumen. However, when the diet offered was deficient in the R vitamins the levels of synthesis were high. There was no apparent relationship between the levels of the vitamins in the food and the levels in the rumen liquid. However, a relationship between the nitrogen intake and the vitamin levels in the rumen was found. This relationship was marked when widely differing levels of B vitamin were fed. The total substitution of the dietary protein (casein) by non-protein nitrogen (urea) did not influence the synthesis of thiamine and riboflavin but did depress the synthesis of nicotinic acid.