Hay, Haylage and Silage: What’s the Difference?

not more than about 12 percent 88 percent DM. Hay that is baled with a moisture level in excess of 12 percent will result in bales that are heavy and at risk of mould and heating. Heating can happen because the presence of sufficient water in the forage allows metabolic activity to continue resulting in heat accumulation within the bale. The heat can get so high that spontaneous combustion and barn fires are the potential outcome. Always strive to buy hay for horses that is not more than approximately 12 percent moisture.
What about silage?
Ensiling forages is a practice where wilted or fresh cut grass is packed into an anaerobic environment. Anaerobic refers to an environment where no oxygen is present. The ensiling process allows the natural microbes on the grass to ferment the natural sugars in the grass water soluble carbohydrates or WSC to organic acids such as lactic acid or acetic acid. As the acids accumulate in the packed forage the pH drops eventually arriving at a point where no more microbial activity can happen. This process generally takes about 21 days to complete. When the pH stops dropping the ensiled feed is considered stable and ready for storage. In order to exclude the air from forages intended for ensiling the bales are generally wrapped in plastic. Each bale is like a mini silo and has its own fermentation process. The quality of the forage that comes out of the bale is determined by the quality of the forage that went into the bale and the completeness of the ensiling process that was allowed to happen.
Forages baled too wet cannot achieve a low enough pH through the fermentation process and are therefore much more prone to spoilage and nutrient loss than drier bales. Less desirable end products of fermentation can result. An example of this is wet round bales that have an accumulation of butyric acid rather than lactic acid as a fermentation end product. Butyric acid doesnt have as low a pH as lactic acid and so it does not preserve the forage as well. It also has an unpleasant smell. Forages that are too moist at ensiling can become compostlike with pockets of rotten silage   definitely not good feed for horses or cattle.
Forages that are baled too dry are difficult to compact enough to exclude all the oxygen allowing aerobic metabolic activity that needs oxygen microbial