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Why Does Hay Spoil?


At moistures 16% to 30%, mold, fungi and yeasts start to multiply, consisting of mycelium and spores, giving the hay a white and dusty appearance, and can also produce harmful mycotoxins. Mold growth also causes heating.


  • Hay baled at moistures 16% to 22% will heat to over 115°F, enough to cause discoloration and loss of the hay’s fresh smell
  • Between 23% and 26% hay can reach temps of over 120°F in storage causing brown to black hay with carmelized mold
  • Moisture levels of over 27% can result in heating to over 140°F and above and may even combust.

Value of Higher Moisture Hay

Baling Alfalfa at 22% vs. 14% Moisture

More tons of dry matter harvested +10%
Extra weight from moisture retained +4%
  Total +14%
24 points higher relative feed value  

“Mechanical Properties Affecting Leaf Loss in Alfalfa”, W.K. Bilanski, CANADIAN AGRICULTURAL ENGINEERING, Vol. 15, No. 1, June 1973

How Thirty Plus Works – Ingredients

Propionic Acid
Buffered so it has a neutral pH avoiding corrosion on equipment, yet it is still effective enough to stop the growth of mold and prevent heating.

Citric Acid
Helps maintain both the fresh smell and green colour of hay, even after it’s stored.

Makes particle size uniform for even dispersing and less risk of under application due to wind drift.

What is Thirty Plus?

Buffered Propionic Acid
Buffered Propionic acid is the most popular type of preservative used on hay between 16% and 30% moisture. While other acids can be used to preserve hay, propionic is the most effective in controlling the molds commonly found in hay. Un-buffered acid has a pH of less than 1 and is therefore very corrosive. The buffering process can raise the pH to 6, the same as rain water, and is much easier to use than straight acid. However, in raising the pH, careful manufacturing procedures must be followed to prevent neutralizing the propionic acid making it much less effective. A truly reacted buffered propionic acid will keep the effectiveness of straight acid and that is what makes Thirty Plus effective on hay up to 30% moisture.

Application Rates – Large Square Bales

Hay Moisture Stem Moisture Dew Moisture Only
Under 22% 6 lbs/ton 3 lbs/ton
23% - 26% 10 lbs/ton 8 lbs/ton
27% - 30% DO NOT BALE 16 lbs/ton

Not recommended on any hay above 30% moisture.

Application Rates – Small Square & Round Bales

Hay Moisture Stem Moisture Dew Moisture Only
Under 22% 4 lbs/ton 2 lbs/ton
23% - 26% 8 lbs/ton 6 lbs/ton
27% - 30% 16 lbs/ton 12 lbs/ton

Not recommended on any hay above 30% moisture.

Benefits of Using Thirty Plus

  • No more waiting on the weather, bale when you’re ready at moistures up to 30%
  • Start working earlier in the day and later in the evening
  • Bale at higher moistures without worry of heating or mold damage
  • Hay treated with Thirty Plus is greener and higher in feed value
  • When compared to dry preservatives and inoculants, Thirty Plus is easier to apply, gives more consistent coverage, and won’t clog application equipment
  • Works well on ALL types of hay
  • Non-corrosive buffered formula won’t harm expensive baling equipment, the user, or livestock
  • Thirty Plus treated hay can be stored for years and will look and feed as well as when it was first baled
  • Thirty Plus is ok to store outside as it won’t freeze and won’t lose effectiveness over time
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