A comparison of the voluntary intake and digestibility by beef cows of diets based on oat straw and supplemented with different forms of non-protein nitrogen

Pregnant beef cows were given 2 kg barley per day and oat strawad libitum. The digestibility of the organic matter of the diet was approximately 53% when urea included in the barley was given in one or four feeds per day. Supplementation of the barley with di-ureido isobutane improved the organic matter digestibility to 56·7%. When a solution containing urea, phosphorus, calcium and sodium was included in the straw the digestibility of the diet was 59·0%. These improved digestibilities were not associated with any differences in the concentrations of ammonia in the rumen liquor or blood of the cows.