Rumen Ammonia Concentration as Influenced by Storage Time, Freezing and Thawing, Acid Preservative, and Method of Ammonia Determination

Twenty-five milliliters of rumen fluid from five cows on a variety of diets were added to either 25 ml .1 N HC1, 5 ml 25% metaphosphoric acid, 5 ml 20% trichloroacetic acid, 5 ml 3 N H2 SO4, or no preservative. Replicate samples were stored at -20C until analyzed. One replicate set was analyzed at 7 d, refrozen and analyzed at 35 d, refrozen, thawed, and reanalyzed at 65 d. Another set was thawed and analyzed at 35 d and yet another set kept frozen until analyzed at 65 d. Fresh and frozen samples were quantitated for ammonia by Conway microdiffusion and phenol-hyp0chlorite reaction.