Effect of Dry Matter Content and Length of Ensiling on Quality of Alfalfa Silage

Abstract

Second cutting, bud-stage alfalfa was ensiled in miniature structures limiting oxygen at four dry matter contents (38.8, 52.1, 57.8, and 65.8%) for three ensiling periods (10, 20, or 30 days). The resultant silage was assayed for various qualities including pH, acid detergent insoluble nitrogen, and lactic, acetic, propionic, and isobutyric acids. Fermentation at dry matter contents of 57.8 and 65.8% resulted in pH elevated above 5.2, high acid detergent insoluble nitrogen (more than .60, percent insoluble protein 3.75 on dry weight basis), low concentration of lactic and acetic acids (less than .5% on wet weight basis), and high concentrations of isobutyrate (more than .09%) indicative of poor fermentation patterns and inferior silage. Although there was no significant effect of dry matter on temperature in the fermentation process, high percentages of insoluble nitrogen and dark color of the silage from two highest dry matters are indicative of a Maillard type browing reaction. Lactic, acetic, and propionic acids increased through 30 days following ensiling, and pH stabilized between days 10 and 20. Acid detergent insoluble nitrogen did not increase after day 10 indicating protein damage in the first 10 days of ensiling.