Nitrogen fractions and in sacco dry matter and crude protein degradability of fresh and frozen alfalfa

Second cut alfalfa was harvested at 163 g kg−1 DM content and processed fresh or after being frozen for 30 days at −18°C. Concentrations of ammonia– and free amino acid–N were clearly increased in frozen samples compared to the fresh crop. Freezing resulted in increased extent of initial dry matter and crude protein disappearance in sacco. Rumen degradability parameters significantly differed from those of the fresh forage with the soluble and potentially degradable fraction being the most affected. The effect of freezing on rumen degradability of alfalfa tended to disappear after 24 h of rumen incubation.