Effect of Modified Atmospheres on Proteolysis and Fermentation of Ensiled Alfalfa1

Two studies evaluated the proteolysis of alfalfa that was ensiled in laboratory silos under different modified atmospheres. In the first study, fourthcutting alfalfa was ensiled at 25% dry matter (DM) for 28 d. The forage treatments were a modified atmosphere of 3% O2:20% CO2:77% N2, or formic acid (6 ml/kg of fresh weight); an untreated control was used for comparison. Proteolysis was assessed from the concentrations 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 NH3 N plus free AA N. Higher silage pH and lower concentrations of total organic acids suggested that the modified atmosphere reduced forage fermentation. The modified atmosphere was effective in reducing proteolysis to a level similar to that achieved with formic acid. Alfalfa ensiled under the modified atmosphere had more peptide N than did alfalfa ensiled with formic acid, which may be advantageous. In the second study, alfalfa was ensiled at 20 and 28% DM as an untreated control or treated with N2 gas or a modified atmosphere composed of 3% O2:15% CO2:82% N2. The NH3 N concentrations were higher in alfalfa ensiled at 28% DM under N2 gas or the modified atmosphere. Concentrations of free AA N were lower at the higher DM percentage for all treatments. Concentrations of NPN were reduced 7.0% for low DM ensiled under N2, 7.0% for high DM ensiled under N2, 23.4% for low DM ensiled under a modified atmosphere, and 25.7% for high DM ensiled under a modified atmosphere. Modified atmospheres reduced the rate and extent of NPN formation in alfalfa silage. (