Forage inoculants: Expectations and handling

Are you using a forage inoculant in your forage program?

The evidence is clear, and the industry’s leading experts agree that it’s no longer a question of “Should I use a forage inoculant?” but rather, “Which forage inoculant should I use?”

Even so, many producers are still not treating their forages, a decision that could be costing them dearly. This could be due to bad past experiences, products not living up to excessive claims made by the sales rep or just wanting to minimize production costs.

Forage innoculants

But remember that inoculants are not all the same, so don’t let one bad experience put you off. What is important is to choose a proven, quality inoculant with the independent research to substantiate its claims.

Remember, too, that an inoculant will not make up for shortcomings in forage management such as poor packing or bad feedout practices. To get the most out of any inoculant, you need to get that right first.

Making a choice

There are lots of inoculants to choose from, so how do you decide?

The most important consideration when choosing a product has to be whether it has independent trial data to support it.

To have confidence it will perform consistently, you need to see evidence from many trials, not just one, especially if that one has been selected from a number of trials because it is the best.

After all, you wouldn’t make a seed variety selection from a single test plot in a single location to plant 100 percent of your acres. Nor would you select a sire for your herd based on the performance of only one or two daughters.

It is important to understand that just because two different inoculants contain the same type of bacteria (e.g., Lactob acillus plantarum) does not mean they are the same.

That would be like saying there is no difference between a Holstein and a Hereford. They may well both be members of the same species (Bos taurus), but they are certainly not the same.

Bearing this in mind, only trials done with a specific inoculant can be used to support it. Yet inoculants without their own trial data often try to ride on the backs of those that do. Statements like “research has shown inoculants to increase performance by 3 to 5 percent” are fine in the right context but not if used to imply that such improvements can be expected from all inoculants.

More correctly, the statement should say that “some” inoculants have shown this.

When reviewing data, be cautious if it looks too good to be true. Marketing specialists are experts at manipulating data to make it look better than it really is.

So, “buyer beware.” Do your homework before you decide, and ask to see the trial data. Reputable, proven products will be happy to provide you with this. It may take a bit more time and effort, but there is a lot at stake, so it will be well worth it in the end.

Handling inoculants

Having bought a good inoculant, it is important to make sure you don’t do anything that will reduce its effectiveness when applied.

The active ingredients in inoculants are live bacteria, which are easily killed if stored or used incorrectly.


It is imperative you handle and store the product according to manufacturers’ recommendations. The bacteria are particularly sensitive to temperature and humidity, so all inoculants have a limited shelf life, even when stored unopened under ideal conditions.

Take note of the expiration date, which typically ranges from one to three years. Beyond this, bacterial numbers cannot be guaranteed. If they have been stored incorrectly, they will fall below specification well before their stated expiration date.

Mixing and application

How you mix and apply the inoculant can affect how well it performs, too. Start the season with a clean applicator system and clean it frequently during the season.

If you use detergent to clean it, make very sure that everything is very thoroughly rinsed with clean water, as even very low concentrations of detergent can kill bacteria.

Feedback from the field tells us that some products don’t mix well, which has led some to use hot water to aid the process. Not a good idea.

The granules may well dissolve better, but the bacteria could end up dead as a result as they are very temperature sensitive. Only use cool to cold tap water.

We are often asked if inoculants can be mixed using chlorinated water. You must follow the manufacturer’s recommendations on this, as some say no and others say yes depending on the level of free chlorine.

Tank mix life

The bacteria in inoculants can be stressed by field conditions such as high water temperatures in the applicator tank. Dr. Limin Kung, Jr. (University of Delaware) and his research group carried out trials to look at this issue.

As you can see (Figure 1), a water temperature of 113°F (only moderately warm) resulted in a significant reduction in bacterial numbers with big differences between the six inoculants tested.

Forage inoculants - expectations and handling

Kung said that a half to one log drop in live bacterial numbers in the tank (e.g., a decrease in numbers from 8.5 log cfu per ml to 8 or 7.5 cfu per ml in the figure) was enough to make an inoculant ineffective.

In a recent study, Kung’s group sampled a large number of applicator tank temperatures in the field during last year’s corn silage season and found that 30 percent of the tanks surveyed had less than 50 percent of the expected number of live bacteria.

Not surprisingly, the lowest bacteria counts were found in the hottest tank mixes – the water temperature in one tank was almost 130°F.

Kung noted that high water temperatures in inoculant tanks are almost always due to being placed too close to heat sources on the choppers.

He recommends, to be safe, tank mix temperatures should be maintained below 100°F to ensure that the inoculant bacteria remain live.

First-generation applicators were simply poly tanks, but with the introduction of low-volume application, we now have small, insulated tanks available which help keep the inoculant cool longer.

If you are going to be harvesting in hot weather, choose an inoculant that has been shown to survive well in such conditions, use an insulated tank if possible and mount it well away from heat sources.

Making up fresh inoculant more often would also help, and although this is likely to be impractical where inoculants are being applied at high-volume rates, in low-volume situations, it is easier.

You spend just a few days each year harvesting the forages you need to feed your cattle for the rest of the year, and forage quality has a big effect on profitability, so it is well worth a bit of extra effort to get it right.

Getting forage management right is critical to success, but using a well-proven inoculant will help maximize final forage quality.