Botulism Prevention with Small Grain Baleage

Mr. Rory Lewandowski, Extension Agriculture Educator, Wayne County, The Ohio State University Extension

Recently, I had a question from a dairy farmer concerning possible botulism in some small grain baleage. Bacteria in the clostridial family are responsible for producing the dangerous toxin that causes botulism. These clostridial bacteria are found everywhere in the soil and are common on plant material during harvest.  Clostridial bacteria are active when forage moisture is high, above 65% moisture. The other condition that serves as a warning signal for the potential production of the botulism toxin is an anaerobic (no air) condition combined with poor fermentation. Poor fermentation is usually indicated by a forage pH of greater than 4.5. Clostridial bacteria will not grow if the pH is below 4.5.

Over the past several years, the practice of planting cereal rye as a winter cover crop and then harvesting that cereal rye as an early spring forage crop has become more common. Another practice where a small grain is routinely used as forage is to plant oats as a nurse crop with a new alfalfa seeding. The oats is then harvested early, typically at late boot to early heading stage of maturity. In either situation, the small grain crop is generally chopped and put into a silo as silage or is cut and baled at a high moisture content and wrapped with plastic as baleage. Both of these harvest methods depend upon fermentation to produce a safe, quality forage.

Good forage fermentation depends upon lactic acid production to reduce pH to 4.5 or lower, ensiling or wrapping at the proper moisture content, and the exclusion of air. Forage pH is a primary indicator of quality and botulism risk in cereal grain baleage. Clostridial bacteria can grow at a pH of 5 or higher. Be very cautious of feeding small grain baleage with a pH of 5.5 or higher. If the baleage has a putrid or ammonia smell to it, this should serve as another warning sign for potential botulism. Producers may wish to test the pH of any baleage which is suspect. Electronic hand-held pH meters can be purchased from most any agricultural supply catalog store, such as Nasco or Gemplers. 

Water-soluble carbohydrates (WSC) provide the sugars needed for the lactic acid-producing bacteria to lower the pH. Cereal forages, such as rye, wheat, and oats, have lower WSC contents than corn or sorghum species, so management practices become very important. Chopping forage helps to bring the WSC located inside plant cells into contact with lactic acid producing bacteria which are on the outside of the plant. The lack of chopping in baleage production is an obstacle to optimum fermentation. Another consideration is weather. WSC content can decline once the forage has been cut, begun to dry down, and then is rained on. As WSC content declines, it becomes more of a challenge to get a low forage pH during the fermentation process.  

Rye, wheat, or oat baleage must be made at the correct moisture percentage to obtain good fermentation and avoid potential problems with clostridial bacteria. Ideally, baleage should be made when the forage is at 40 to 60% moisture. Strive for a 50% moisture average on bales. As mentioned earlier, clostridial bacteria that produce the botulism toxin like wet conditions. Small grain baleage at greater than 65% moisture increases the risk for botulism toxin production. Also, the risk for bolulism in baleage increases with increased soil contamination and baling of dead animals within the forage.

Excluding air and getting a dense, tightly packed bale is another important step to get good forage fermentation and to produce a safe, quality baleage product.  As rye, wheat, and oats mature, this becomes more difficult because fiber content increases and the plants are not as pliable. Bales should be wrapped as quickly as possible. A good goal is to wrap within 2 hours of baling, but certainly no later than 8 to 10 hours after baling. There is quite a lot of research that indicates a minimum of four layers of 1 mil plastic is needed to get a good seal on the bale, and the plastic should be UV resistant. If bales are going to be stored for long term (greater than 6 months), applying six layers of plastic is recommended. Inspect bales on a regular basis and patch any holes in the plastic with tape made specifically for plastic.