Forage Preservatives

Hay, haylage, or silage preservatives will reduce storage losses from moulds, bacteria, and fungi when the forage is put up at higher moisture contents.

There are many types of hay preservatives with various effects. The various products can be grouped into the five following categories:

I. Organic Chemicals

Classification	Examples	Effect of Preservative
1) Volatile fatty acids and their salts	Propionic acid Acetic acid Ammonium propionate	These acids reduce the pH of the forage material. Applied at low rates they discourage yeasts and mould growth and may encourage a lactic acid fermentation. When applied at high rates, the acids inhibit all microbial activity. Concentrated organic acids work at moisture levels of about 25 per cent. The acids are corrosive but generally effective.
2) Other organic acids	Formic acid Lactic acid
3) Ammonia producing compounds	Anhydrous ammonia Urea	Ammonia is an effective fungicide (prevents mould and yeast growth). The nitrogen from these sources can be utilized as a nutrient by ruminants. Anhydrous ammonia is effective up to and above 30 per cent hay moisture. The product is applied at the rate of 2 per cent of dry forage weight.

II. Inorganic Chemicals

Classification	Examples	Effect of Preservative
1) Inorganic acids	Sulphuric acid Orth phosphoric acid	These acids reduce the pH of forage material and prevent breakdown and losses of forage nutrients by (a) reducing activity of the plant's own enzymes, and (b) inhibiting microbial activity.
2) Drying Agents	Potassium carbonate Sodium carbonate Sodium chloride Calcium chloride Magnesium chloride	These salts remove water from the forage material and thereby reduce microbial activity. Under ideal conditions dessicants can increase the rate of dry-down by 50 per cent.

III. Biologicals

Classification	Examples	Effect of Preservative
1) Inoculants	Lactobacilli Pediococcus	Inoculation of forage material with desirable acid-producing bacteria helps to initiate a rapid fermentation and sustain a rapid fall in pH of silage. In hay it may reduce the harmful effects of mould and yeast.
2) Enzymes	Cellulose Amylose Lactobacillus (non-viable) bacteria	These enzymes promote plant cell breakdown and render the cellulose and starch more accessible to desirable acid-producing bacteria.

IV. Nutrients

Classification	Examples	Effect of Preservative
1) Fermentation Mediums	Molasses & sugars Whey Starch (cereal by-products)	Encourage fermentation by providing an energy source for desirable bacteria.
2) Nutrient Additives	Anhydrous ammonia Urea Calcium carbonate Sodium sulfate Molasses	Usually nitrogen or mineral additives, they make a contribution to the nutrient value of the forage for livestock. In some cases the additive will improve both nutrient value and fermentation quality.

V. Non-specified Additive Ingredients

Classification	Examples	Effect of Preservative
1) Antioxidants		Enhance chemical activity and may maintain a 'green' color.
2) Sodium metabisulfite	Ethoxyquin	In contact with moisture, this compound forms sulfur dioxide gas and a sulfite salt. These compounds reduce microbial activity.

Hay preservatives and additives have been used with varying degrees of success.

In Manitoba, experiments with organic acids have given satisfactory results on both hay and silage trials. In general, though, acids are not widely used because they are very corrosive and unpleasant to handle.

Other trials in Manitoba have shown anhydrous ammonia to be very effective in preventing moulds and yeasts in both hay and silage. Anhydrous ammonia is a non-protein nitrogen source which increases the nutritive value and the digestibility of the forage to livestock. The use of granular urea on silage can perform the same function. Even distribution of the product is essential.