Now that the silage is in the bunk, silo or bag, the process of fermentation is under way.

Many have begun using inoculants during harvest to improve their silage quality. So now that you added an inoculant, what could go wrong?

Last year, treating some alfalfa and corn silages with an inoculant did not appear to benefit the producer with improved silage fermentation. But was it the inoculant? The forage? The applicator?

The answer is, “It depends.”

So, while you are too late to make changes for this year’s forage, you never are too late to document your silage success for future harvests. Let’s start with a review.

What is an Inoculant?

Silage inoculants contain anaerobic (that means they survive without oxygen) bacteria that produce lactic acid. Bacteria in commercial products usually contain one or more of these species: Lactobacillus plantarum or other Lactobacillus species, various Pediococcus species and Enterococcus faecium. These bacteria have been selected to grow rapidly and efficiently, resulting in an increased fermentation rate. In addition, the products of fermentation include higher levels of lactic acid and lower levels of acetic acid.

The primary economic benefits of using an inoculant include improved dry-matter recovery and animal performance. Applying inoculants can reduce dry-matter losses 2 to 3 percent in a well-managed bunk. The shift in fermentation products (higher lactic acid and lower acetic acid) should increase animal feed efficiency because animals can utilize lactic acid more efficiently than acetic acid.

Do Inoculants Always Work?

Well, you know the answer to that: It depends. Not all conditions are conducive for inoculation. According to research conducted at the U.S. Department of Agriculture’s Dairy Forage Research Center in Wisconsin, the success of an inoculant is most impacted by the size of the natural population of lactic acid bacteria on the crop. The greater the natural population, the less the bacteria (non-native lactic bacteria) added by inoculation will be able to dominate the crop and provide a benefit during fermentation.

The populations of natural lactic acid bacteria increase with long wilting times (greater than two or three days), rainfall during wilting and higher wilting temperatures. Inoculants will work best when applied to forage harvested at the recommended moisture contents for the various storage structures (45 to 70 percent moisture). Natural populations of lactic acid bacteria do not grow well under dry conditions, suggesting that inoculants may be more successful when used with drier crops.

Which Inoculants Should You Use?

Many inoculants are on the market, and comparing them is difficult. However, you have some key factors to consider when purchasing an inoculant that may help improve success.

First, look for a product that guarantees to supply at least 90 billion live lactic acid bacteria per ton of crop. Certain strains of lactic acid bacteria are selected for particular crops (corn or grass, for example); therefore, make sure you purchase an inoculant labeled for the crop that you are going to ensile.

Liquid and dry inoculants are commercially available. Either type can do the job; however, liquid formulations have some advantages vs. dry. Liquid applications generally are more uniform, begin to work faster and are easier to store (they come in smaller packets that can go in the refrigerator) than dry products.

However, if using a liquid inoculant, avoid chlorinated water (less than 1 part per million) because it can kill the bacteria. If you have chlorinated water, purchase inoculants that contain compounds that will neutralize the chlorine.

Not all inoculants are created equally, so don’t be afraid to ask the dealer for product research, preferably done by an independent researcher.

Once you purchase an inoculant, proper storage (cool and dry conditions) will help maintain bacterial viability. Improper storage of your inoculant can result in the death of the bacteria, and dead bacteria are useless. For these reasons, some producers experience poor or no benefit from applying an inoculant.

Tips for Applying Inoculants

Bacteria added to silage will not move; they grow where they are placed; therefore, uniform coverage is essential for maximum effectiveness. A liquid sprayed on the crop at the chopper provides the best opportunity for the product to distribute and mix uniformly in the harvested crop. You have many other ways to apply inoculant, but this does not include throwing dry inoculant onto a wagonload of forage and hoping for even distribution.

Using the recommended rate is important. Application of less, or more, of the inoculant will not be helpful and is a waste of money. If unused liquid remains 24 hours after it was mixed, it should be discarded because the bacterial population will have begun to decline.

Do not apply inoculants to silage that already has completed fermentation. Inoculants, when used properly, can improve silage quality and animal performance.

Remember, inoculants are one tool that will improve silage quality; however, they are not a replacement for good management practices. Proper chop size and adequate packing are still important to assure an oxygen-free environment. Wilting the forage before storage also is extremely important to not only reduce seepage, but increase forage sugar content (an important food source for the bacterial inoculant).

A quick review of your ensiling management practices and documenting them now before you forget may help explain why you did not see the results you were expecting when using an inoculant.

For more information, several good references are available. They include “The Silage Zone” by DuPont Pioneer, “Silage Management Handbook” from Lallemand Animal Nutrition and “Silage Inoculants” by Charles Hansen.