EFFECT OF MODIFIED ATMOSPHERES ON PROTEOLYSIS AND FERMENTATION OF ENSILED ALFALFA

Two studies evaluated the proteolysis of alfalfa that was ensiled in l aboratory silos under different modified atmospheres. In the first stu dy, fourth-cutting alfalfa was ensiled at 25% dry matter (DM) for 28 d . The forage treatments were a modified atmosphere of 3% O-2:20% CO2:7 7% N-2, or formic acid (6 ml/kg of fresh weight); an untreated control was used for comparison. Proteolysis was assessed from the concentrat ions of NH3 N, free amino acid (AA) N, and nonprotein N (NPN). Peptide N was estimated as the difference between total NPN and the sum of NH 3 N plus free AA N. Higher silage pH and lower concentrations of total organic acids suggested that the modified atmosphere reduced forage f ermentation. The modified atmosphere was effective in reducing proteol ysis to a level similar to that achieved with formic acid. Alfalfa ens iled under the modified atmosphere had more peptide N than did alfalfa ensiled with formic acid, which may be advantageous. In the second st udy, alfalfa was ensiled at 20 and 28% DM as an untreated control or t reated with N-2 gas or a modified atmosphere composed of 3% O-2:15% CO 2:82% N-2. The NH3 N concentrations were higher in alfalfa ensiled at 28% DM under N-2 gas or the modified atmosphere. Concentrations of fre e AA N were lower at the higher DM percentage for all treatments. Conc entrations of NPN were reduced 7.0% for low DM ensiled under N-2, 7.0% for high DM ensiled under N-2, 23.4% for low DM ensiled under a modif ied atmosphere, and 25.7% for high DM ensiled under a modified atmosph ere. Modified atmospheres reduced the rate and extent of NPN formation in alfalfa silage.