Forage conservation includes drying (hay-making), fermentation (silage-making) and feed additives like urea treatment of straw. In general, if forage can grow year-round, this will be of better quality, making forage conservation superfluous. Where forage growth is highly seasonal, forage conservation can offer a way to balance forage supply to animals, but moderate weight losses during a dry season are quickly regained through compensatory growth in the next wet season. Wetter material is not easy to store, it needs to be covered and kept under anaerobic conditions. Larger units have less waste than smaller pits. Silage and urea-treated straw are better suited for medium-sized or large animal holdings. The biotechnology in these techniques will make little contribution to alleviating poverty among smallholders. Silage and urea-treated straw have a shorter storage life than hay because wet material cannot be transported as easily as can dry material, their use is also less flexible. Top quality silage can be made without the addition of any additives or preservatives. There is no reliable evidence that adding enzymes, yeast cultures, antibiotics or acid-forming bacteria will increase the feeding value of corn silage. The two additives most often used in corn silage are limestone and non-protein nitrogen compounds. Molasses and grain may be added to corn forage at the time of ensiling. However, this practice only tends to enrich the resulting corn silage as a feed rather than to improve the quality of the corn forage itself. There is also some fermentation loss with the added molasses and grains.