Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/16/1997
Publication Date: N/A
Citation: Interpretive Summary: The wrapping of large round bales with stretch-wrap plastic films to make silage is an increasingly popular means of preserving forages. Unfortunately, the ideal moisture content for ensiling by this method is not known. Most recommendations are to bale at moisture contents of 50 to 70%, typical of silages made in other silo types. However, in practice farmers frequently make round bale silage at moisture contents below 50%. To determine the effect of moisture content on preservation, ryegrass and legume-grass round bales were made over a range of moisture contents (25 to 65%) at each of four farms in Eastern Oklahoma. The bales were wrapped with six layers of stretch film and stored outside for six months. Estimated dry matter losses were low at all farms (2 to 12%) and were not higher in the drier bales as we had expected. Changes in quality characteristics such as crude protein, neutral detergent fiber, acid detergent fiber and total digestible nutrients were consistent across farms and were not affected by the moisture content of the bales. Silage fermentation was reduced in the drier bales. However, spoilage losses appeared to be similar across moisture contents below 65%. These results suggest that the quality of forages at moisture contents above that considered safe for dry storage (approximately 20%) but less than that acceptable for well-preserved silage (approximately 50%) can be maintained through bale wrapping as long as the plastic film is not damaged.
Technical Abstract: At four farms in Eastern Oklahoma, round bales of ryegrass and legume-grass silage were wrapped with stretch film. Initial bale moisture contents ranged from 25 to 65% wet basis. After six months in storage, apparent dry matter losses (range of 2 to 12%) were not affected by initial moisture content. Ensiling produced significant increases in crude protein and acid detergent fiber contents and reductions in total digestible nutrients whereas neutral detergent fiber content was unaffected by ensiling at three of four farms. However, changes in these quality factors were not significantly affected by initial moisture content. Final moisture content of core samples from 0-10 and 10-23 cm depths ranged from 14.0% to 71.7%. Moisture content had a significant effect on fermentation. Ryegrass silage samples above 50% moisture content had average lactic and acetic acid contents of 2.5% and 0.5% DM while legume-grass silages averaged 1.0% and 0.4%, respectively. Of the 312 samples analyzed, 17.9% had pH values above 6.5, indicating spoilage. This proportion was unaffected by moisture content for samples having moisture contents less than 65%. Consequently, these results suggest that the quality of forages at moisture contents above that considered safe for dry storage (approximately 20%) but less than that acceptable for well-preserved silage (approximately 50%) can be maintained by eliminating available oxygen for microbial decomposition through bale wrapping.