Some livestock producers always use inoculants on their hay-crop silage, but not on their corn silage.

That's a mistake, says Kansas State University silage guru Keith Bolsen.

Research has shown that inoculant treatments lead to fermentation improvements about two-thirds of the time in hay-crop silages, but just 40% of the time in corn silage. Yet Bolsen is sold on them.

“The question for dairy and beef producers isn't ‘Should I use an inoculant on corn silage?’ It's ‘Which inoculant am I going to use?’” he says.

At the root of many of the misconceptions about using inoculants on corn silage, says Bolsen, are the natural properties of the crop itself.

“Corn is an almost perfect silage crop,” he notes. “It has lots of sugar (for conversion to lactic acid during fermentation), a low buffer capacity and a suitable dry matter content. About the only thing that would make it better for growing cattle and lactating dairy cows would be for it to have more protein.”

In comparison, hay-crop silages (especially alfalfa) have a low sugar content and very high buffer capacity. In short, they're more difficult to ensile.

“With alfalfa, you use an inoculant to try to reduce the risk of poor-quality fermentation or failed fermentation,” says Bolsen. “But with corn, you're not going to have a fermentation failure.

“When you use an inoculant on corn, you're trying to make a good silage even better by getting more control over the important fermentation end products — a high lactic acid content and low amounts of acetic acid, alcohol and ammonia-nitrogen.”

Using an inoculant on corn silage also makes sense from a cost-benefit standpoint, says Bolsen.

“At today's prices, the cost of using an inoculant on corn silage in beef and dairy operations pencils out to 1-2¢/head/day,” he says. “I can't think of any other technology in beef or dairy that will give producers as consistent a response for that kind of cost.”

Among the things to consider when selecting an inoculant for use with corn silage, according to Bolsen:

  • Application rates

    Focus on the number of lactic acid bacteria applied per unit of crop. Bolsen recommends buying a product that calls for applying at least 100,000 CFUs (colony forming units) per gram of crop. Higher numbers of bacteria should work better than this recommended minimum, but that's not always the case.

    “It's not cast in stone,” says Bolsen.

  • Bacteria strains

    Most inoculants contain multiple strains of lactic acid bacteria. The most common strain is Lactobacillus plantarum. Other Lactobacillus or Pediococcus species and Enterococcus faecium are also common. It probably pays to be a little skeptical of products that contain other species, he notes.

  • Differences in strains

    There are lots of variation in how strains of bacteria in different products work. For example, not all Lactobacillus plantarum strains grow at the same rate. Some strains may grow better on alfalfa; others on corn. Some strains may grow better under drier vs. wetter conditions or at higher vs. lower temperatures.

“There really is no one best inoculant product out there,” says Bolsen. “And there are all kinds of different philosophies on what a good inoculant should contain and what it should look like. That means the No. 1 thing you can do when choosing a product is make sure your supplier or distributor offers solid technical support.”