Spring harvest is quickly approaching and now is the time to review management practices to prevent possible botulism and listeriosis health risks associated with poor quality small grain baleage.
Many dairy farms plant a small grain crop such as winter wheat, cereal rye or triticale in the fall with plans to harvest that crop as an ensiled or baleage product.
Health risks are greatly reduced when small grain forage is managed to promote a good fermentation process.
During the fermentation process, anaerobic bacteria convert sugars in the harvested forage to lactic acid. A good fermentation process will produce enough lactic acid to lower the forage pH to 4.5 or lower.
At a pH of 4.5 bacteria in the Clostridia family responsible for botulism and the listeria bacterium responsible for listeriosis, as well as other spoilage organisms, are prevented from growing.
Good fermentation is dependent upon harvesting at the right growth stage, ensiling or baling at the proper moisture content and eliminating air to create and maintain an anaerobic environment.
Small grain baleage presents some challenges to achieving adequate fermentation and pH values of 4.5.
According to an April 2015 article in an Extension beef newsletter from the University of Kentucky, written by Michelle Arnold, DVM-UKY, and Ray Smith, UKY forage specialist, those challenges include the following.
Wrapped long stem hay has less sugar availability for microbes. Because the forage is baled rather than chopped, the sugars must diffuse from inside the plant to reach the lactic acid bacteria on the outside of the forage. As forages mature sugar content decreases so there is less sugar for the fermentation process.
Lower bale density makes round bale silage more susceptible to either entrapment or penetration of oxygen, increasing the chance of air pockets (and subsequent spoilage) within the bale.
Wet or non-wilted forages are more likely to spoil. Bacteria from the Clostridia family thrive in wet environments where forage moisture is in the 67 to 70 percent range. Greater than 70 percent moisture almost guarantees Clostridial growth and spoilage.
Water-soluble carbohydrates (WSC) provide the sugars needed for the lactic acid-producing bacteria to lower the pH.
Small grain forages have lower WSC content than corn or sorghum species so management practices become very important. The sugar content of plants decreases as the plant matures.
Small grain forage harvested at boot or earlier stage maturity is more likely to undergo good fermentation as compared to mature, high fiber, stemmy small grain forage.
Cereal rye, wheat, triticale or oat baleage must be made at the correct moisture percentage to obtain good fermentation and avoid potential problems with clostridial bacteria and the bacterium Listeria monocytogenes.
Ideally, baleage should be made when the forage is at 40 to 60 percent moisture. Strive for a 50 percent moisture average on bales.
As mentioned earlier, clostridial bacteria that produce the botulism toxin like wet conditions. Small grain baleage at greater than 65 percent moisture increases the risk for botulism toxin production.
Make dense, tightly packed bales to remove air pockets and help to prevent air from entering the bale.
As small grains mature this becomes more difficult because fiber content increases and the plants are not as pliable and do not pack as well.
Use of a bacterial inoculant can help to accelerate the rate of fermentation and improve the stability of the forage during feed out. Use inoculant rates of at least 100,000 colony forming units per gram.
Bales should be wrapped as quickly as possible to minimize heat damage and limit dry matter loss.
Wrapping within two hours of baling is desirable, however, research indicates that forage quality is generally maintained if wrapping occurs within 12 hours after baling.
The plastic should be pre-stretched 50 to 70 percent before it is wrapped around bales and if bales will be stored outdoors, the plastic should also be UV resistant.
Dennis Hancock, University of Georgia forage specialist, recommends applying six or more layers of plastic on individually wrapped bales and eight or more layers on in-line wrapped baleage.
Bales need to be checked regularly during storage and any holes or punctures should be promptly patched.
It is generally recommended to wait at least eight weeks after wrapping before feeding baleage.
This will ensure that a full fermentation has taken place and that the silage is stable and will not deteriorate or heat when it is fed.
The key indicator of adequate fermentation and a safe ensiled forage is pH. Be cautious of feeding small grain baleage with a pH of 5.5 or higher.
Both clostridium botulinum (responsible for the botulism toxin) and Listeria monocytogenes (responsible for listeriosis) can grow in this environment.
A small grain baleage with a pH of 6.0 or higher is a definite red flag.
Small grain baleage can be a high quality, palatable feedstuff when managed properly to avoid potential health risks.