Do silage inoculants work?
Thomas Quaife
| Wednesday, September 01, 1999
If you feed the best stuff to your cows, everything else will fall in line. That's always been Robert Strack's attitude.
Silage is no exception. He's seen the difference between silage that went into the pit with inoculant on it and silage that had been left untreated. The inoculated silage looks and smells like good silage. The other stuff, well.... it "just stinks," says Strack, manager of Morwai Dairy in Hudson, Colo., a facility with nearly 3,000 cows.
He's not sure how much extra milk production the dairy is getting from using silage inoculants. It's one of those "six of one, half a dozen of another" type of things, because if they weren't using silage inoculants they might be making other adjustments in the ration. But, he's confident that a better-looking, better-smelling feed must be doing good things for his cows.
Look at the research
Of course, many of you will want to know exactly what impact the silage inoculant is having on milk production. It won't be easy, however, given all of the variables on your farm, including the weather. But, you can gain some clues from the research.
Richard Muck, agricultural engineer at the U.S. Dairy Forage Research Center in Madison, Wis., and Limin Kung, professor of ruminant nutrition and microbiology at the University of Delaware, looked at research that had been done on silage inoculants from 1990 through 1995. They found that inoculants were successful in reducing pH and shifting fermentation toward lactic acid more than 60 percent of the time.
Why not 100 percent of the time, you ask?
Well, too many variables may have confounded the results. And, remember, the trials looked at a number of silage inoculant products.
Some trials were conducted on corn silage, some on alfalfa, some on grass silage. Some were conducted in England, some in the United States. Trials were conducted under different management systems.
Kung acknowledges the type of literature review that he and Muck conducted needs to be taken with a grain of salt. "It is true that grouping this data all together is not the best way to look at the effectiveness of inoculants, since some products certainly have more supportive data than others," he adds.
Bottom-line: Some products perform better than others. The strains of lactic acid bacteria found in some products are superior to those found in other products.
Consider the unknowns
There are some things we just don't understand about silage inoculants and the way they work. While it's possible to measure the pH of the silage, or even the ratio of lactic acid to acetic acid in the end product, some things may be happening that we can't measure.
Much of the research is based on the ending or "terminal" pH of the silage. But, terminal pH doesn't tell you how quickly the silage reached that point - an indication of fermentation quality, says Bill Mahanna, senior ruminant nutritionist at Pioneer Hi-Bred International. "It tells you where you are at today, but doesn't tell you what happened to get there."
And, terminal pH does not correspond well with some of the feed parameters affecting milk production, such as rate of digestion.
Traditional forage analysis doesn't always provide the needed answers. The labs don't measure rate of digestion, for instance, and that means one of the biggest potential advantages of inoculants goes unnoticed.
Suffice it to say, a good silage inoculant will improve the quality and rate of fermentation that takes place in the silo. That, in turn, appears to translate into reduced dry matter losses and improved animal performance.
Gain more milk
Some of the research trials on silage inoculants look quite promising.
Joe Harrison, animal scientist at Washington State University, found in one trial that milk production was 3.5 pounds per day higher among cows fed silage that had been treated with an inoculant from Pioneer Hi-Bred International, compared to cows fed untreated silage.
But, no one is suggesting that you will get 3.5 pounds more milk every time.
"I'm not about to walk on a farm and tell somebody, 'you're going to see 3 pounds per cow per day,' because a lot of it's dependent on how that silage is handled, how long it's in front of the cows, and what kind of bunk face management they've got," Mahanna says.
Kung agrees. Based on the field trials he has reviewed, Kung says the boost in milk production from silage inoculants appears to average 1.5 to 2 pounds per day.
Is it cost-effective for a producer to go after that extra 1.5 to 2 pounds?
Yes, Kung says. If you are getting an extra 1.5 to 2 pounds per cow per day, "you are definitely paying for the product," he says. "You're probably getting more than a 3:1 to 4:1 return on investment."
Helpful advice when purchasing silage inoculantsv
Generally speaking, silage inoculants are a worthwhile investment, says Limin Kung, professor of ruminant nutrition and microbiology at the University of Delaware.
Kung, who has studied silage inoculants extensively and is a leader in the field, issues a few cautions, however, when purchasing these products.
First and foremost, purchase from a reputable company.
Kung says three companies in particular - Pioneer Hi-Bred International, ECOSYL Products, Inc., and Chr. Hansen BioSystems - are doing a good job. Their products have shown favorable results in research trials.
Make sure the product is delivering live lactic acid bacteria. Dead bacteria do you no good. Of course, there's really no way for a producer to know if the bacteria are alive or not. That's why it's so important to buy from a reputable company.
Demand animal performance data from your supplier. Consider what kind of technical expertise the company has with silage products.
Some companies claim that their products supply a form of bacteria known as Lactobacillus plantarum - just like the major suppliers do. But, you must realize there are major differences between L. plantarum strains. Saying that all L. plantarum are alike is like saying all Holstein cows are alike.
What do inoculants do to the silage?
When you add silage inoculants, you are trying to shift fermentation in a certain direction.
Basically, you're adding "good bugs" to the mix, so that the fermentation will produce more lactic acid than might otherwise occur. The good bugs, also known as lactic acid bacteria, overwhelm the other bugs that are naturally present in the silage.
"Traditionally, good fermentation is what people consider homolactic fermentation, which, on a theoretical basis, means that you only make lactic acid and don't make any other end-products," says Limin Kung, professor of ruminant nutrition and microbiology at the University of Delaware. But, on a practical basis, that doesn't occur with 100 percent efficiency. The role of silage inoculants is to shift the process toward homolactic fermentation as much as possible.
