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.

Most biological products have a provisional licence for sale in Canada. Products on the marketplace with a temporary registration will be allowed a period of up to one year to substantiate label claims or else be removed from the marketplace. At the present time, many bacterial inoculants are being evaluated by research institutions and universities in Canada. Insufficient research data is available at this time to discuss product effectiveness.