ENUMERATION OF LACTIC-ACID BACTERIA ON HARVESTED ALFALFA AT LONG AND SHORT WILTING TIMES

Preservation of alfalfa as silage relies on the presence and activity of lactic acid producing bacteria (LAB) at ensiling. Counts of LAB wer e determined on standing, mowed, and harvested alfalfa for two growing seasons under Northeast conditions, and were used to test prediction equations based on Wisconsin data (Muck, 1989b, 1990, 1991). Wilting t imes, rainfall quantities, and wilting temperatures were outside the r ange of the Wisconsin data in 60 of 70 trials. The equations performed well when conditions were in the range of the original data. For shor t wilting times, the inoculation associated with chopping was assumed to be affected by rainfall and wilting time only up to 4 mm and 72 h, respectively, and to be unaffected beyond that. LAB counts at wilting times greater than 72 h were predicted best by average ambient tempera ture and rainfall during wilting. The equation for long wilting times was independently verified with separate data from Wisconsin not used in previous regressions. Use of inoculants is projected to be cost eff ective on direct cut material when the average temperature in the 24 h prior to harvest is less than 23 degrees C with no rainfall. For long wilting times, average wilting temperature must be less than 20 degre es C for inoculants to be cost effective, but the temperature must be lower as rainfall increases.