Protein Preservation and Ruminal Degradation of Ensiled Forage Treated with Heat, Formic Acid, Ammonia, or Microbial Inoculant

¹ Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315

The objectives of this study were to determine whether treatment of forage with heat would reduce proteolysis during subsequent fermentation. In Experiment 1, direct-cut barley forage and alfalfa were untreated, microwaved, or steamed and then ensiled in laboratory silos as wilted forages. Silages of microwaved or steamed forage showed a marked increase in N bound to neutral detergent fiber and in the recovery of protein; however, alfalfa silages also had high pH values and concentrations of butyric acid. In Experiment 2, steam heating was compared with formic acid and NH₃ treatments for the prevention of proteolysis in alfalfa silages. Silage of steamed alfalfa had a greater amount of N bound to neutral detergent fiber and greater recovery of protein than did control silage or silages of forage treated with formic acid or NH₃. Silage of steamed forage had lower pH values than did silages of wilted, direct-cut, or control forage. Microbial inoculant added to steamed forage increased the recovery of protein. Silage of steamed forage had less aerobic stability than did silage of direct-cut forage. Ruminal degradability of crude protein (CP) and organic matter of silage from both experiments was evaluated. Degradability of CP was 8 to 26 percentage units lower in silages of microwaved or steamed forage in Experiment 1 than in silage of unheated forage because of slower degradation rates, but all had similar undegraded CP after incubation for 72 h. In Experiment 2, wilting, steam, formic acid, and NH₃ treatments affected CP degradability similarly, but CP degradability was decreased when compared with silage of direct-cut forage without treatment.

Key Words: forage • protein preservation • heat and chemical treatments

Submitted on May 12, 1997
Accepted on October 2, 1997