Changes in Nitrogenous Compounds and Sites of Digestion of Alfalfa Harvested at Different Moisture Contents

Samples of fresh alfalfa and alfalfa wilted to dry matter contents of 29, 40, and 66%, collected before and after ensiling, were analyzed for compositional changes resulting from wilting and ensiling. Wilting and ensiling had little effect on total nitrogen content of alfalfa but produced substantial changes in the profile of nitrogen-containing compounds in the forages. Five Holstein cows fitted with rumen cannulae and with T-type cannulae in the proximal duodenum and terminal ileum were employed to study effects on nutrient digestion of feeding the three alfalfa silages and baled hay. Forages supplied approximately 75% of the nitrogen consumed by the cows. Cows fed silage of 66% dry matter had a higher percentage of dietary nitrogen equivalent recovered as nonammonia nitrogen at the duodenum because of less extensive ruminal degradation of dietary crude protein. Treatment did not affect intestinal availability of nitrogen. Intakes (g/day) of amino acids were different because of dietary forage, but profiles of amino acids entering and absorbed from the intestine were similar for all treatments. Availability of amino acids in the small intestine was unaffected by source of forage.