The most important factor affecting the success of an inoculant is the size of the natural population of lactic acid bacteria on the crop: The higher the natural population, the less likely the inoculant will succeed. In alfalfa, the natural population varies with wilting conditions. The natural population is increased by higher average wilting temperatures, longer wilting times, rainfall during wilting and higher moisture contents at chopping. Consequently, these conditions, rather than cutting, are important for determining the best time to use an inoculant on hay-crop silage.

Under typical conditions, the profitability of an inoculant will be more variable in the first cutting than in subsequent cuttings. This is true because we typically have longer wilting times and a greater likelihood of rainfall during wilting in the first cutting, which reduce the chances for an inoculant to succeed. However, do not assume that using an inoculant in the first cutting is unprofitable.

Inoculants may contain one or more strains of lactic acid bacteria. The most common is Lactobacillus plantarum. Other Lactobacillus or Pediococcus species may be present; Enterococcus faecium also is common. Rarely, a Bacillus species may be present to improve bunk stability. Be skeptical of products that contain other species.

Comparing inoculants is difficult, but here are some things to do when purchasing a product:

  • Look for a product that guarantees to supply at least 90 billion live lactic acid bacteria per ton of crop.
  • Be sure to buy a product that is labeled for the crop you are going to ensile.
  • Ask for research, particularly independent research data, to back up the product manufacturer’s claims.
  • Once you have purchased a product, be sure to store and use it according to directions.

Costs vary by products and the volume you buy. The typical cost is $1 per treated ton of crop, but it can range from 60 cents to more than $2 per ton.

An inoculant should work well at any of the recommended moisture contents (between 45 and 70 percent moisture) for the various silo types. However, fewer types of naturally occurring lactic acid bacteria will be able to grow well under drier conditions. This suggests that inoculants should be successful more frequently in drier crops.

Can inoculants increase milk production in the dairy cow?

Increases in animal performance have been observed more often than increases in intake. A survey of inoculant studies in all silage crops found milk production improved in about half of the studies. In those studies where milk yield was improved, the average increase was 3 pounds per cow per day.

Are forage inoculants cost-effective?

When appropriate inoculants are applied to ensiled forages, they are cost-effective. Several factors influence the degree of response from inoculants, but on average, net returns increase when inoculants are used on silages.

At present, responses to hay inoculants are quite variable. Additional research and development is necessary before hay inoculants offer the degree of economic benefit noted for silage inoculants.