Studies on the Disappearance of Nitrate in Forage Crops during Ensilage : VII. The relationships between the disappearance of nitrate and the bacteriological changes during ensilage

Abstract

In order to investigate the effect of addition of glucose at ensiling and pre-wilting to medium moisture level on the disappearance of nitrate and the bacteriological changes with special reference to the changes in nitrate reducing bacteria during ensilage, Italian ryegrass containing large amounts of nitrate was ensiled in laboratory silos. In each experiment, the silos were kept at 28℃ in the incubator in triplicate and opened at 3, 7, 15 and 60 days after ensiling. The results obtained from this experiment were as follows: 1. The silages without glucose addition (control) were of extremely poor quality, rate of nitrate disappearance being from 97.0 to 100%. The glucose-added silages and the medium moisture silages were of good and medium quality, respectively. The rate of nitrate disappearance in glucoseadded silages was 4.4 to 28.2%, but that in medium moisture silages was different in two experiments, being 100 and 38.2%. 2. In the first few days after ensiling, a rapid decrease of nitrate reducing bacteria occurred in all silages, but the extent of the declining was in different among three treatments. Counts of nitrate reducing bacteria in the medium moisture silages were largest and those of the glucose-added silages were smallest. 3. In the glucose-added silages, rapid growth of lactic acid bacteria occurred, the counts reaching to a peak at 3 to 15 days after ensiling. The counts of lactic acid bacteria in the control silages at 60 days considerably decreased and the level was lower than those in medium moisture silages.