Effect of Moisture Level of Material Grass on Silage Fermentation

Silage experiments were carried out to study the effects of moisture level of the material grass on the microbiological processes and chemical quality. Orchardgrass (Dactylis glomerata L.), a third cut, harvested on 1 October was chopped by hand, and then following four kinds of treatments were employed, (a) unwilted, (b) light wilt, (c) moderate wilt and (d) heavy wilt, by pre-wilting. The treated grasses were ensiled in the grass tubes (30 × 200mm) equipped with fermentation seals. The silos were incubated at ambient temperature (about 12-19℃) and the sequence changes in chemical quality and in viable micro-organisms numbers of silages at 0, 3, 7, 14, 21, 28 and 56 days after ensiling were measured, respectively. The moisture contents of material grasses (a), (b), (c) and (d) were 84, 70, 64 and 56%, respectively. The total numbers of micro-organisms in silages (a), (b) and (c) markedly increased on the 3rd day and were 4.6 × 10x , 1.4 × 10y and 1.1 × 10x /g fresh weigh, respectively. But, the micro-organisms counts in silage (d) reached 6.0 × 10w /g fresh weight on 7th day. Then, the total numbers of microorganisms in all silages declined progressively and thereafter increased gradually in the later stages of fermentation. There were no appreciable differences in num-bers of micro-organisms among the silages (a), (b) and (c) at the 56th day, but in silage (d) the numbers of micro-organisms were lower than those of other three silages. The numbers of lactic acid bacteria in all silages increased rapidly the first 3-7 days after ensiling, thereafter increased gradually except silage (a). In silage (a) the numbers of lactic acid bacteria fairly decreased temporarily on the 14th day. The numbers of lactic acid bacteria on the 56th day were 1.9 × 10x , 1.5 × 10x , 9.3 × 10w and 7.1 × 10w /g fresh weight for silages (a), (b), (c) and (d), respectively. The sequence changes in lactic acid contents in all silages during ensilage were closely related to the numbers of lactic acid bacteria, and were in contrast to pH values. The lactic acid contents on the 56th day were considerably higher in silage (a) than in silages (b), (c) and (d) in that order.The ratios of volatile basic nitrogen to total nitrogen (VBN/TN) in all silages became higher with time, and were also higher in high-moisture silage than in low-moisture silage. The water soluble carbohydrate (WSC) content of the material grass was decreased by pre-wilting, and the contents of WSC in all silages decreased gradually with time during ensilage. The rate of increase of volatile fatty acids (VFA) in silage (a) was faster than in others, and the greater part (92% or more) of total VFA on 56th day was acetic acid in all silages