Effects of Temperature and Glucose Addition on the Process of Silage Fermentation

Effects of the temperature during ensilage(30°and 15°)and glucose addition at ensiling on the process of silage fermentation were investigated with laboratory silos. The materials were orchardgrass or Italian ryegrass of 80~87% moisture and 0.391~1.25% (of fresh matter) soluble carbohydrates. When no additive was applied, silages kept at 30° were of very poor quality without exception, while those kept at 15° was generally of fairly good quality. Glucose addition(2%)resulted in excellent quality irrespective of the temperature. The number of lactobacilli increased and then decreased more rapidly at 30° than at 15°. Maximum counts of lactobacilli had no relation to the silage quality though the counts on 70th day of ensilage were higher at 15°. Extent of protein breakdown was affected by temperature at the early stage and by pH at the later stage of ensilage. It is well known that the quality of silage is related to the temperature of the mass in silo1~8)and that the microflora of silage is affected by the temperature durlng ensilage9~11. In early days,"cold fermentation"was associated to butyric acid fermentation which led to poor silage quality1,3). However. , there are some informations that higher temperature in a certain range is favorable for the butyric acid fermentation or is responsible for poor quality of silage2,3,5,7,8). As for the stimulation for desirable lactic acid fermentation, the effect of sugar addition at ensiling has been well established1,6,12~14). In the experiment described here, the effect of temperature(30°and 15°)on the silage fermentation was investigated with different material grasses, and, based on the information obtained, the possibility of glucose addition to overcome the deteriorating effect of the higher temperature was investigated. Materials anal Methods Material grass, silo and ensiling method:Orchardgrass and Italian ryegrass were used as the silage material, some properties of which are shown in Table 1. Urea was top-dressed at the rate of 20 kg per 10 are on 8,11 and 20 days before harvesting the grass of Exp.I, Exp. III and Exp. V, respectively, in order to obtain high-protein material grass. One-liter glass bottles equipped with mercury seal were used as the experimental silos as described in the previous paper15). The grass was chopped to about 1 cm length immediately after harvesting and then packed * Studies on Various Factors Affecting Silage Fermentation , Part 11. Jap. J. Zootech. Sci.,44, (1): 59-67. 59 1973. 1. OHYAMA, MASAKI, and MORICHI in the silos as firmly as possible. In the case of glucose addition, the additive was well mixed with the chopped grass at the rate of 2% prior to ensiling. The amounts of ensiled grass were 750g for Exp. I and II,600g for Exp. III and IV, and 650g for Exp. V and VI. Table 1. Materials ensileda) a) I and III~VI.Orchardgrass, II. Italian ryegrass b) % on dry matter basis c) % on fresh matter basis Treatments: Experiments were carried out according to the following design: Exp. I and II-Effect of the temperature (30°and 15°) on the quality of silage was observed. Exp. III and IV-Effect of the temperature on the process of the silage fermentation was examined. Exp. V and VI-The relation of the temperature and glucose addition was investigated with the four treatments; (1) 30°-control,(2) 15°-control,(3) 30°-glucose addition,(4) 15°glucose addition. The silos were kept in the incubators set at 30° and 15°, respectively, and were opened 70 days (Exp. I and II),7,21,42 and 70 days (Exp. III and IV) or 2,4,7,14 and 70 days (Exp. V and VI) after ensiling and the contents were subjected to analysis. Changes in the counts of total bacteria and lactobacilli and the process of protein breakdown were investigated in Exp. V and VI. In this experiment, the environmental temperature was controlled as described above. But, because the scale of the experimental silo was small, it is supposed that the temperature of the silage reaches equilibrium with the environmental temperature in a short time8). Therefore, it is considered that the "temperature" in this experiment represents that of the silage. Analyses: Extraction for the chemical analysis and lactic acid estimation (colorimetry by BARKER and SUMMERSON) were carried out according to the previous paper15). Gas chromatography of volatile fatty acids (VFA) was performed by the method of MASAKI and OHYAMA16), Volatile basic nitrogen (steam distillation at pH 9.5) and protein nitrogen (trichloroacetic acid insoluble N)were estimated as described in the previous paper17). Viable counts of total bacteria and lactobacilli were enumerated with the samples obtained by homogenizing 10g of fresh grass or silage with 40ml of sterile distilled water in a Waring blender under aseptic condition. Compositions of the plating media were as follows (in 1l); MRS agar for total bacteria18); 10g polypeptone,5g meat extract,5g yeast extract (Difco), 2g K2HPO4, 1g diammonium hydrogen citrate,209g glucose,1g Tween 80,5g sodlum acetate, 5ml mineral solution*, 0.1g L-cysteine,15g agar-pH6.6-. * Mineral solution : 10g MgCl2•E6H2O, 2g MnCl2•E4H2O, 0.08g FeSO4•E7H2O were dissolved in 300ml water.