Whatever you call them, probiotics, or direct-fed microbials (DFM), they promise a lot. Testimonials on company websites declare these little-known microbes can add pounds, improve animal health and reduce morbidity. Yet, unbiased, large-scale university research on the use of these type of products by cattle producers seems to have reached no clear consensus.
A 2012 study by a team at Kansas State University (KSU), for example, focused on the beef side of the business. Researchers looked at 279 crossbred stocker heifer calves over 44 days. Average weights were just under 500 pounds. Half of the calves were given ProTernative SF, an active dry yeast product. The treatment, according to the KSU report, "had no effect on average daily gain or dry matter intake." The study concluded the product had no influence on growth performance or morbidity rate.
Dale Blasi, one of the authors of the research and Extension beef specialist at KSU, says it's common in the case of DFMs to see nonsignificant and/or inconsistent health and feed efficiency responses.
Good Insurance? "If you do get a positive response, generally once you put the numbers to it (cost), it doesn't pay," Blasi says. "I've seen receiving yards and feedyards use these products as insurance, hoping they can alleviate intake problems with certain sets of calves. But, it's not something that shows a consistent response time and time again."
He says because DFMs are GRAS (generally recognized as safe), there is no FDA oversight. Costs of the products can average anywhere from 1 cent to 3 cents per head per day.
Blasi adds the outcome of the 2012 study doesn't, in his mind, mean there is no future for DFMs in the beef industry. Rather, he says he's hopeful as research continues new treatments will be developed with the efficacy, predictability and consistency the industry needs. Until then, he encourages producers considering use of a probiotic to do their homework before selecting a product and to keep detailed records so they can make their own determinations regarding cost effectiveness.
One of the oldest companies in the DFM business, Bio-Vet Inc., was founded in 1991. It researches, manufactures and markets DFMs and nutritional products for dairy and beef cattle, small ruminants and horses.
Ron Martin, product manager, says they've seen a boost in business since the Veterinary Feed Directive (VFD) ended the use of antibiotics as growth promotants.
"Our business in the cattle industry, with both dairy and beef, has remained fairly steady," Martin says. "But, we've seen an increase in the use of DFMs, or probiotics, for raising calves."
Bio-Vet uses two strains of Propionibacteria, P-5 and P-63, in several products. These strains date back 20 years. Bio-Vet sources them from another company for use in final manufacturing of its DFMs.
Martin says it's important to choose DFMs from reputable companies with a long history, as well as those with the research to back up the efficacy of their specific strain(s) of microbes.
A Ph.D. dissertation Bio-Vet points to in its company literature, "The Impact of Propionibacterium on Ruminal Acidosis in Beef Cattle," was published by Oklahoma State University in 1997. This dissertation, by Dara Lynn Swinney-Floyd, is used as a source for Bio-Vet's own research article, which notes select Propionibacterium strains are beneficial to animals and can "survive in an acidic rumen environment."
Bio-Vet reports these strains convert lactic acid to propionate, influence dry matter intake and reduce toxic compounds. Swinney-Floyd's work supports this: "Propionibacterium strain P-63 possessed the attributes necessary for ruminal survival and the antiacidotic activity to reduce the potential for acidosis to occur in cattle being rapidly adapted to high concentrate diets."
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The experiment included daily doses of P-63 starting 14 days prior to the introduction of concentrates in feedlot heifers' diets. The concentrate included 75% ground wheat and was fed at a rate of 2.5% of body weight each day.
DFMs In Dairy Calves
While the VFD may have a lot more beef producers looking at DFMs these days, Michael Hutjens, dairy specialist and professor emeritus for the University of Illinois' department of animal sciences, says use of these products is fairly common in milk-fed dairy calves and goes back to the 1980s.
"We've seen nice responses to probiotics in milk-fed calves," he says. "They are still simple-stomached animals, and they aren't getting much dry feed."
Research shows once a starter feed, or grain, begins to be consumed by a calf, it takes about a month for the rumen to develop.
Hutjens says a common practice with dairy calves is to use a probiotic paste on pre- or nonweaned animals, or added to the milk or milk replacer. Some dairy farmers add DFMs to calf starters or electrolyte drenches. The dairy specialist believes this helps calves make that transition to feed and may protect the small intestine from harmful bacteria. He adds, research on the dairy side, such as beef, is still limited when it comes to consistency, efficacy or cost effectiveness.
"I don't have a problem believing, however, that anytime a calf is under stress, a probiotic could help—maybe with electrolytes, yeast cells or buffers," Hutjens says. "You are basically trying to stabilize the digestive tract and maintain dry matter intake."
The Rumen Challenge
Geof Smith, a veterinarian and professor of ruminant medicine at North Carolina State University, is hopeful these products will be able to do all they promise one day, but he's not onboard when it comes to their present-day effectiveness.
"Probiotics have a track record of success in some species, humans and swine, for example. Those are simple-stomach animals. When you are using a probiotic, you want to get the beneficial bacteria to the small intestine. This might not be that difficult in a human or a pig, but when you're a steer, that probiotic has to survive through the rumen and be able to colonize the small intestine. It's a lot to ask, especially in numbers great enough to make a difference in the rumen environment."
Smith says he has yet to see convincing, unbiased research showing DFMs are effective in beef cattle with fully functional rumens. He goes so far as to add: "Probiotic cocktails probably are not effective in cattle. Maybe we'll figure out how to turn on the immune system with these products one day to prevent disease, but we're not there yet."
Nutrition's Role. Ted Perry, cattle nutritionist with Purina Animal Nutrition, says he wants to see more than company white papers and in-house studies to base his assessment on probiotics.
"The biggest problem now, as I see it, is that with any of these type supplements, most of the evidence research companies have is anecdotal," Perry explains. "I tell producers they want to be able to see that when you use X product under this set of circumstances, 85% or better of the time, you will see a predictable result. The truth is we can't do that."
He adds the 85% number is key, because it means the data is as accurate as the data for vaccination program efficacy.
In an adult cow's normal functioning healthy rumen, Perry says each milliliter of rumen fluid contains about 10 billion bacteria. A cow has more than 45 gallons of rumen fluid.
"When we start talking about adding a probiotic, you have to consider what we're being told. Say that probiotic has 1 million of a particular type of microbe, or bacteria, that you feed each day. I already have 10 billion in 1 milliliter in a 45-gallon rumen. Do I care about 1 million? Can that really make an impact? If a probiotic manufacturer has a bug strong enough to make a consistent impact at that miniscule amount, they would need some pretty strong data."
A Good Balance
Perry likes to consider the probiotics question in the realm of nutrition. He is a firm believer in giving cattle what they need when they need it and then getting out of their way.
"They do a good job without a lot of help," he says, adding even micronutrients only work when everything else is in balance. That means minerals, protein and energy all need to be in balance.
"When you get a cow on a balanced diet, it's difficult to show much improvement with additives," Perry continues. "If you're going to add something to the rumen, the best benefit is likely to come from something that grows more rumen microbes."
The fewer microbes there are in the rumen the less ability a cow has to efficiently digest forage, so there is less energy created. A cow can only eat more forage when what is already in her system ferments and empties.
The Time Factor. Perry notes as seasons change, producers don't always do a good job of getting protein and energy supplements out to the herd early. He advises thinking in terms of where hay fields are on quality as a good rule of thumb for supplementation timing.
"As we go through the grazing season, consider that if a hay field is 9 or 10% protein, what are the pastures? We tend to bale hay in June or July, and never think to supplement the cows then. But, we need to look at it from the standpoint that if we need to bale hay to preserve quality, we should be supplementing the cow herd with protein and energy."
He advises a good mineral program to keep immune function strong and supplementing early to avoid the need to rebuild lost body condition or a weakened immune system. Manure consistency is an old-fashioned but excellent indicator of how well the rumen is functioning, and of forage quality. When cow piles start to stack up, it's evidence fiber is being passed through the system not fermented in the rumen. That, Perry explains, means feed efficiency is going down. Start to supplement energy and protein, and he predicts manure will change back to more traditional, flat, round piles.
Much of the push for use of DFMs has focused on stressed calves, especially those being switched over to feed. Perry says it takes three to four weeks to move a calf to a higher grain diet, because rumen bacteria have to grow that can digest starch and grain. He's not convinced a probiotic can speed up Mother Nature's timetable.
"Years ago, I took my first ruminology class, and I talked to my dad about why we moved calves over to that starter diet slowly," Perry recalls. "He didn't care that rumen microbes took a month to change over. He just knew that what he did as a cattleman worked. A lot of what we do is the right thing already, whether we know why we do it or not."
Perry says there is some evidence yeast products and yeast metabolites can bring some positive benefit to certain sets of calves.
"I believe we do usually see an increase in immune status of those animals. That's where we are right now," Perry explains. "Even this doesn't work all the time. I go back to the point that if I have a very well-balanced diet, and my rumen microbes are going great guns, I don't get any value from these products. I already have all I need for that animal in the rumen."
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