A High Roughage System for Raising Calves Based on Early Rumen Development. IV. Synthesis of Thiamine and Riboflavin in the Rumen as Influenced by the Ratio of Hay to Grain Fed and Initiation of Dry Feed Consumption

Abstract

Rumen thiamine and riboflavin levels and the quantity of these vits. excreted daily in the urine remained practically constant when different ratios of hay to grain (4:1, 3:2, and 2:3) were fed using either alfalfa or mixed clover-timothy hay with a simple grain concentrate mixture. It is concluded that rumen synthesis of these vits. was neither augmented nor depressed by feeding different ratios of hay to grain when good quality legume or mixed legume hay was fed. When mature timothy hay was fed, highly significant differences were observed in rumen vit. levels between groups of calves fed different ratios. Rumen thiamine levels were max. when a 4:1 ratio of hay to grain was fed and were min. when either all timothy hay or a high proportion of grain concentrate mixture was fed. Rumen riboflavin content increased with increased levels of grain concentrate feeding to calves fed timothy hay until a max. riboflavin synthesis was attained at the 2:1 ratio of hay to grain. This high rate of synthesis was maintained at higher levels of grain feeding. Thiamine synthesis was depressed in calves which had been fed rations containing a 2:3 ratio of hay to grain when the ration was abruptly changed to a 4:1 ratio. Results were presented which show the favorable effect of ingestion of dry feed (40-80% good quality clover-timothy hay) on the synthesis of thiamine and riboflavin in young rumen-inoculated calves. The possible relationship of thiamine and riboflavin synthesis to the growth and establishment of certain varieties of rumen microorganisms when different ratios of hay to grain are fed was discussed.