Advantages of using forage preservatives

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The efforts to improve the management of forage storage will result in a good return to producer’s investment. Hay, haylage, or silage preservatives will reduce storage losses from molds, bacteria, and fungi especially when the forage is harvested at higher moisture levels. Limited microbial growth occurs in dry hay, generates a small amount of heat, and usually raises temperatures very slightly (Figure 1).

Figure 1: Typical storage temperature profiles in dry and moist hay. A brief elevation in temperature could occur during the first couple of days in hay at 20% moisture. Hay with higher moisture level will reach higher temperatures and heating might be prolonged.
Source: Collins and Owens, 2002.

Excessive microbial growth can raise temperatures to 130 to 150oF, increasing dry matter loss and producing Maillard reactions that reduce dry matter and crude protein digestibility (Collins and Owens, 2002). Effective preservatives to inhibit microbial growth or artificial drying to remove excess moisture help to avoid quality and yield loss in moist hay (Collins and Owens, 2002). Effective hay preservatives include (1) organic acids, (2) buffered acids, (3) ammonia sources (i.e. anhydrous ammonia or urea), (4) inoculants, and (5) enzymes.

  1. Organic acids (propionic and acetic acids): will inhibit mold growth and will help to reduce heating and dustiness in hay. Their effectiveness in hay depends on the application rate of active ingredients and moisture content. Application rates near 10 lb/ton are needed for hay with 20-25% moisture, while 20 lb/ton are needed for wetter hay with 25-30% moisture. Some issues with the use of organic acids are related to late season mold growth. Mold inhibition of acid products tends to decrease after long periods of hay storage. The acid eventually dissipates during storage while the moisture remains in the hay.
  2. Buffered acids (Ammonium propionate and propionic acid; Figure 2): are effective in control heating in moist hay but corrosiveness, high acidity, and difficult working conditions has limited their use.
  3. Ammonia sources (Anhydrous ammonia or urea): effective reducing microbial growth in moist hay and can improve fiber digestibility by acting on lignin-carbohydrate bond in cell walls. However, it is important to recommend ammoniating low quality roughage for forages with less than 5% crude protein and 45% of total digestible nutrients (TDN). Ammoniating higher quality forage can cause toxic compounds to be formed. In terms of livestock component, ammonia increases non-protein N, which can help to meet the protein needs for a dairy or beef cattle. Anhydrous ammonia is an effective preservative for hay containing less than 30% moisture. As for urea, it is safer to handle than anhydrous ammonia and has similar benefits for storage and fiber digestibility. Relatively large amounts (5-7% of estimated bale weight) of urea applied during baling can be effective up to 30% moisture. However, treated hay must be covered or processed with a bale wrapper.

    Figure 2: Effect of moisture or ammonium propionate preservative on heating small square bales.
    Source: Collins M, 1995.

  4. Inoculants: bacterial inoculants (i.e. lactic acid) are being promoted as an alternative to chemicals for improving hay preservation.  How does it work? Bacteria is added to water and sprayed on hay as it is baled.  The bacteria multiply and grow during the early stages of forage preservation (after baling) and help to preserve the hay.  These products can be used in hay with moisture content of 25% moisture.  Interestingly, not a lot of research has been done in order to examine their effects in large rectangular bales over a range of moisture contents.  Research suggests that lower moisture content may be necessary to be effective for safe storage. 
  5. Enzymes (cellulose, amylose, and lactobacillus): These enzymes promote plant cell breakdown and render the cellulose and starch more accessible to desirable acid-producing bacteria.

Pro’s and Con’s of using forage preservatives

Organic acids:

  1. More expensive than inoculants
  2. Non-corrosive, buffered products are readily available
  3. Higher application rates gives better results
  4. May be stored and used at will

Non-protein Nitrogen:

  1. Best for corn and cereal crops only
  2. Not recommended for hay
  3. Will inhibit mold development
  4. May improve crude protein slightly

Bacterial Inoculants:

  1. Less expensive
  2. Easy to handle
  3. Not recommended for rained-on hay
  4. Not recommended for late season hay
  5. Require uniform application for consistent results
  6. Must be applied immediately after mixing

Enzymes:

  1. Less expensive
  2. Easy to handle
  3. Reduces fiber content
  4. Not recommended for rained-on hay
  5. Not recommended for late-season hay
  6. Does not directly ferment or prevent mold development
  7. Require uniform application for consistent results
  8. Must be applied immediately after mixing

References:

  • Collins M and Owens V (2002) Hay and silage preservation. In R.F. Barnes, C.J. Nelson, M. Collins, and K. Moore (eds.), Forages: The Science of Grassland Agriculture, vol. 2. Ames, Iowa: Iowa State Univ. Press. P: 443-469
  • Huhnke RL (2003) Round bale hay storage. Oklahoma State Cooperative Extension Service. F-1716
  • Mahanna B (2001) Hay additive review; “where we have been, where we are going”. Nutritional insights. P: 1-12

Source: Karla Hernandez



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John    
midwest  |  July, 25, 2013 at 03:00 PM

How is it that a dry granular bacterial inoculant can have any effect on dry hay (up to 25% moisture), given the bacteria are inactive until they "re-hydrate"? Base on what this article is saying, a dry granular bacterial inoculant would not be effective or recommended? And if a bacterial inoculant were to be used it should be in a liquid (rehydrated) form? John


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