INORGANIC NITROGEN SUPPLY EFFECTS ON ALFALFA FORAGE QUALITY

Objectives were to evaluate the nutritive value of alfalfa treated with N. Alfalfa germplasms, Turkistan and Flemish, were grown in three growth chambers with N supplied at 0, 3, 5, and 10 mM N as ammonium nitrate. Alfalfa regrowth was harvested after 34 d. Digestibility, NDF, ADF, and permanganate lignin did not differ among rates of N application or between germplasms. Ammonia and pH of fluid from ruminal incubations also did not differ. Concentration of N of alfalfa increased as rate of N application increased. Nitrate N concentration increased from .17 +/- .03% for the rate at 0 mM N to .75 +/- .06% for the rate at 10 mM N. Gas production decreased from 19.4 ml/100 mg of forage with the rate at 0 mM N to 12.3 ml/100 mg of forage with the rate at 10 mM N. Gas production was correlated with N concentration (r = -.72) and with nitrate concentration (r = -.82). Ruminal microorganisms incubated with alfalfa treated with 10 mM N produced 21% less total VFA and less propionic acid than microorganisms incubated with alfalfa treated with 0 mM N. Nitrate added to untreated alfalfa reduced gas production similarly to treated alfalfa and also had no effect on digestibility. Application of high concentrations of N to alfalfa can lower energy available to ruminants.