Preservatives are cost effective if used only when needed to prevent rain damage to hay, and if applied uniformly to windrow as it is entering the baler. When purchasing preservatives, compare cost on a per pound of propionic acid basis. Other additives do little, if anything, to preserve hay. Some hay preservative products dilute the proponic acid and require greater product use rates. Note that rates are for pounds of propionate, not product.
Anhydrous ammonia is an effective preservative for grasses.
It can be injected into bales or released into a stack of bales covered and tightly sealed with plastic. Currently, evidence is not sufficient to indicate that microbial hay preservatives are effective in preserving hay. The most common type of bloat is frothy bloat where gas builds up in a foam or froth above the rumen contents and normal belching is inhibited. Observable bloat can occur after as little as 15 minutes of grazing. Often the animal bloats only mildly and stops eating.