Studies on stable method for making of low-moisture round bale silage and evaluation of its quality

Round bale forage packing systems are common all of Japan due to their high labor efficiency. However, it is difficult to dry hay enough to keep round bales without quality deterioration caused by molding, leaf loss and/or leaching of minerals in rain under Japanese climatic conditions. To resolve this problem, found bale silage (RBS) system that each round bale is wrapped with stretch plastic film has been adopted lately. RBS is convenient for transporting and now commercialized. Previous studies indicate that the optimal moisture content for the production of RBS is 50-60%. Therefore, it has been recommended not to make RBS with low moisture content (20-50%) because the quality is spoiled by the possible proliferation of aerobic bacteria. However, minimization of bale weight by reducing moisture content is important for transportation of silage. Then the development of stable method for the production of low-moisture RBS is required. Furthermore, standardization of the criteria for evaluating the quality of low-moisture RBS is necessary for marketing of forage. This study was conducted to develop a method for making and marketing good quality low-moisture RBS. The objectives were (1) to determine the optimal number of wrapping film layers and optimal moisture content for keeping high quality of low-moisture RBS, (2) to examine the effect of the color of wrapping film on fermentative quality and bound protein (BP) content, (3) to determine the effect of maceration on in sacco degradability and digestibility and (4) to standardize the criteria of forage quality. For these purpose, the experiments were carried out in Hokkaido district from 1994 until 2000. 1 In order to determine the optimal number of wrapping film layers and optimal moisture content for keeping high quality of low-moisture RBS, timothy (Phleum pratense L..) was used in the experiments. The numbers of film layers used for wrapping were 2, 4, 6 or 2+2 (2 layers wrapped in the usual direction followed by 2 layers wrapped in the reverse direction). The moisture contents of the silage were 20C 40 or 50“. No mold was observed after 2 months in silage bales wrapped with 4 or 6 film layers. The mean temperatures at the center of those bales ranged from 25 to 30 deg C. Silage fermentation was poor, but V-score, which was proposed by MASAKI (1994), increased as the dry matter (DM) content increased. The dry matter intake (DMI) per metabolic body size of silages with 20C40, 50% moisture contents and of hay made from the same herbage were 49, 53, 43and@51g/kgBWE0.75/d, respectively. After 11 months of storage, mold was not observed in silage bales wrapped in 4, 6 or 2+2 film layers, and there were no differences in chemical composition or