Using Preservatives and Drying Agents to Improve Hay Quality

• Drying Agents: Accelerate dry-down rates, reducing wilting periods, and prevent heating and mold development thus maintaining palatability
• Preservatives: Allow baling at higher moisture levels (up to 18%) for dry hay and green feed, and improve fermentation quality in silage.

• Dry Hay & Green Feed: Hay preservatives—such as acids, bacterial inoculants, enzymes, and other compounds—allow hay to be baled at 18–25% moisture, reducing field drying time and minimize dry matter losses and leaf shatter
• Silage: Enhances fermentation and feed quality.
• Flexibility: Useful for “odd” crops or challenging weather conditions.

• Product Selection: Review CFIA’s list of registered non-nutrient forage additives for tested and approved products.
• Buyer Beware: Products not registered with CFIA may lack research validation and could be ineffective.
• Read Labels: Follow manufacturer guidelines for application rates and safety.

• Apply preservatives only to high-quality forage cut early or at the optimum stage.
• Preservatives do not improve poor-quality, mature forage.

• Bacterial/enzyme inoculants work best on crops with high sugar levels.
• Avoid use on late-season crops with low sugar content, as mold prevention will be ineffective.

• Severely weathered or rained-on hay is a poor candidate for preservatives.
• In such cases, only acid-based products are recommended.

• Accurate moisture testing is critical for correct application rates.
• Moisture levels fluctuate during the day with temperature and humidity—apply preservatives only when conditions are not optimal for safe baling.

• Preservatives are useful in fields with:
• High variability in moisture and plant species.
• Numerous wet spots.

• Preservatives do not protect hay from rain or snow.
• Always cover treated hay with tarps or store in sheds to protect your investment.

• In Canada, many hay preservatives are registered for use, though availability may vary by region.
• Products are generally sourced through local dealers along with applicator equipment.

• Applicator Setup Matters:
• Proper calibration is critical for accurate application rates.
• Adjust nozzle type, pressure, and positioning for full coverage.
• Biological Inoculants:
• Ensure product viability before use for effective results.

• Bacterial inoculants
• Enzyme-based products
• Combination products

• Less expensive and easy to handle
• Not recommended for rained-on or late-season hay
• Requires uniform application and immediate use after mixing

• Ineffective on rained-on hay due to rapid microbial growth
• High CFU rates needed post-rain (up to 5,000,000 CFU/g DM) are uneconomical—acid treatments are better in these cases

• Do not directly prevent mold
• May improve digestibility, especially in mature, high-fiber forage or silage
• More effective at higher moisture levels
• Not recommended for dry hay
• Can be stored long-term (check product-specific requirements)

• Low application rates: Discourage yeast and mold growth; may encourage lactic acid fermentation.
• High application rates: Inhibit all microbial activity.
• Storage advantage: Can be stored and used anytime, reducing waste.

• Approximately 3 times more expensive than biological preservatives.
• Buffered and neutralized acid products now dominate the market:
• Maintain effectiveness without corrosive damage.
• Reduce volatilization losses compared to older concentrated acids.

• Small square bales:
• 0.5–1% for 20–25% moisture
• Up to 1.5% for 31–35% moisture
• Large bales: Require higher rates for best preservation.
• Higher rates generally yield better results.

• Inhibit mold and yeast growth
• Reduce aerobic microbial activity and heating at feed-out
• Increase crude protein (CP) content

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.

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.

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.

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.

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.