CONSERVED FORAGE ( SILAGE AND HAY ) : PROGRESS AND PRIORITIES

Forage conservation permits a better supply of quality feed when forage production is low. While haymaking and ensiling have been practiced for generations, research is still needed to 1) understand the processes affecting quality during harvesting and storage and 2) develop practical means to minimize losses and enhance quality. Several trends in harvesting forages for silage are notable. Kernel processing of maize, once confined to Europe, has become popular in North America. Self-propelled forage harvesters have a larger share of the market due to more contract harvesting and larger farms. Larger harvesters, rakes and mergers help improve productivity and forage quality. Finally, farmers are increasing cutting length to meet the fiber needs of high-producing dairy cattle. These latter two trends make good silo management more critical. The number of silo types has continued to increase. Pressed bag and wrapped bale silages are important recent developments. These newer types have made it easier to segregate silages by quality and allow small farms to make high quality silage. However, disposal of the larger quantities of plastic is a growing issue. Alternatives such as edible or biodegradable films would be welcome for all silo types, reducing labor and environmental concerns. With wrapped bales, spoilage and listeria contamination are more common because of the large surface to volume ratio. Enhanced methods to control spoilage and pathogen development are needed. With most crops considerable breakdown of true protein occurs during ensiling, subsequently decreasing nitrogen utilization efficiency in ruminants. The polyphenol oxidases in red clover and the tannins in some legumes reduce protein loss during ensiling. These mechanisms may be useful in developing new silage additives or plant varieties. Additives can enhance silage quality. Inoculants are the most common. Improved inoculants aimed at increasing aerobic stability are beginning to be marketed, but their overall success is uncertain. Enzymes to degrade plant cell walls, providing sugar for fermentation and making the silage more digestible, have not fulfilled their promise but do have potential. Acids and sugars have been declining in use but still are important in certain ensiling situations. Three types of balers are used to package dry hay: small square (SSB), large round (LRB) and large square balers (LSB). The SSB is declining importance in developed countries because of labor constraints but remains viable in developing countries where farm labor is still plentiful. The LRB is the dominant baler worldwide because of its productivity and low ownership and operating costs. High productivity and a package ideally suited for shipping has promoted the continuing growth of the LSB. Hay producers struggle with getting crops dry enough (< 20% moisture) to prevent excess storage losses due to biological activity. This is especially important as bale density increases. Typical bale densities are about 130, 190 and 240 kg/m for SSB, LRB and LSB, respectively. In humid climates, forage researchers and producers are investigating intensive conditioning systems to improve field drying rates, utilizing preservatives like propionic acid, and developing bale ventilation and drying systems all in the attempt to improve dry hay quality. In arid regions, producers only bale after dew accumulation has softened brittle plant tissue to reduce leaf loss. Systems are under development that will soften plant tissue at the baler by applying a fine water mist. Larger livestock farms and increased development of markets for commercial hay will push demand for greater productivity and better bale quality.