The fate and effects of duodenally infused casein and urea nitrogen in sheep fed on a low-protein roughage

Abstract

Urea and casein infused per duodenum into sheep fed on a low-protein cereal hay produced elevated blood urea and rurninal ammonia concentrations. Compared with casein infusion, urea treatment resulted in greater and more rapid rises in both blood urea and ruminal ammonia concentrations.

Cellulose digestion rates were increased after infusion of either material, but casein tended to exert its effect at a later time. Of 10 g of nitrogen infused in each form, urinary excretion accounted for 5 g with urea treatment, but only 3 g when casein was given. Results are discussed in relation to mechanisms for conservation of urea nitrogen in sheep fed on low-protein diets. Attention is drawn to the implications of these findings in relation to the effect of casein infused per duodenum upon voluntary intake of low protein roughages.