Horse management practices have drawn from many sources, but the link between an increasingly popular system for improving digestion in the horse and turn of the century Bulgarian peasants is perhaps one of the most exotic. Shortly before World War I, a Russian biologist set out to determine why certain Bulgarian and Russian people lived so long. Eventually, he cited the regular consumption of fermented milk products, for example yogurt, as the source. His idea was that a bacteria found in those foods, Lactobacillus acidophilus, improved digestion, giving the people a better shot at staying healthy and getting the most out of the food they ate.

Skip forward several decades, and animal scientists began researching the practice of feeding compounds that promote the growth of certain bacteria in the gut of animals. The products began to be known generally as probiotics (combining the Greek words that mean for and life). The term was coined by Richard Parker, a microbiology professor at the Oregon Medical School, in the 1960s.

The concept behind probiotics is simple: a host of flora live in the digestive system of any animal. As the animal eats, these microorganisms in the digestive tract help digest and utilize that food. Because of this added bacterial assistance, the animal gets the maximum nutrients from the food, which improves growth, production (if that is part of the animal's role), and resistance to disease.

If something causes a shift in the type or balance of microorganisms in the digestive system, a number of problems can result. The animal simply might not derive as much benefit from the food as it should, making feeding less efficient. Harmful bacteria can take over the digestive tract, giving rise to illnesses (including diarrhea) that can be dangerous to the animal. The horse also will be more susceptible to other disease as overall health deteriorates in light of inadequate nutrition.

The development of probiotics to enhance the beneficial flora and fight the harmful flora in the digestive tract came into use first for food animals because of the constant demand to increase production--milk from cows, eggs from hens, or meat from chickens, pigs, or cattle. Results were positive. Administering probiotics was seen to help the animals stay healthy, despite the stress of intense management, and increase production. About 20 years ago, probiotics went into common use among equine managers for helping foals with digestive stress--particularly diarrhea--recover.

Fred Winters, a Thoroughbred horse farm manager in the Lexington, Ky., area who now distributes a line of probiotics, said he became convinced of their efficacy after using them on foals. Winters figured that if the foals improved with the use of probiotics, it should be beneficial for other horses under his care.

"It was so cheap to use, I decided to try it on all the horses and see what happened," Winters recalled thinking.

He was pleased with the results. His horse population seemed to eat less, gain weight more easily, stay healthier, and look better.

"It insures a population of beneficial bacteria, and that alone is worth a lot in preventing the production of pathogenic bacteria that will give your horse a bellyache," Winters says.

Winters' observations were confirmed when a veterinarian who worked with him commented that his horses seemed to withstand the stress of illness or surgery better than others. With that endorsement, Winters began to look into distributing the product.

The horse industry, while always looking for ways to improve management and performance, is sometimes resistant to change. The concept of using probiotics as part of the regular program for a healthy horse past the foal stage is not one that was immediately embraced. Winters pointed to a couple of problems he thinks have slowed acceptance.

First, some probiotics were mislabeled and, as a result, probiotics containing microorganism appropriate to swine were administered to horses. Some foals died as a result. Winters said the reaction of some horsemen was: "That's probiotics, and it kills Thoroughbreds. I'm not going to use that anymore."

Although Winters was one of the horsemen who lost a foal, he did not lose faith in probiotics. "I had a lot of work to do just to get people to use this stuff, and I gave a lot of this product away," he says.

The more persistent problem in acceptance, Winters says, is the lack of quantifiable evidence relating to horses.

"The difficult thing for a horse person to accept is a lack of scientific evidence, but it's really hard to quantify in a horse things that we are trying to get done. It's easy to measure average daily gains (in beef or other meat animals), it's easy to measure milk production, but how do you measure that your horse is dappled and has a shiny coat?"

Still, Winters believes probiotics are an important part of management for horses, particularly those regularly subjected to the stresses of training, racing, sales preparation, and other intense management practices that are common today.

Management Tips

"One of the body systems most likely to succumb to such stressful conditions is the intestinal tract, which constitutes a doorway for pathogenic microorganisms," wrote Ana J. Montes, DVM, and D.G. Pugh, DVM, MS, Dipl. ACT, Dipl. ACVN, in an article in Veterinary Medicine about pro-biotics. Although Montes and Pugh said it is not known exactly how probiotics work, "administering probiotics to reinforce the beneficial intestinal microflora," can prevent some of the deleterious effects of stress.

Winters particularly recommends pro-biotics for horses undergoing sales preparation where a healthy coat appearance and appropriate weight are critical to success. Winters said some farms he services that ship stallions to the Southern Hemisphere buy a supply of probiotics to send with the horse to ease the stress of the trip and help in the animal's adjustment to a new locale.

Montes and Pugh noted that regularly feeding antibiotics to stem growth of harmful bacteria in the digestive tract can become self-defeating over time.

"The indiscriminate use of broad-spectrum antibiotics may alter intestinal flora by suppressing normal bacteria and allowing overgrowth of pathogens," they wrote.

Montes and Pugh set out the criteria a manager should look at in selecting a probiotic. First, the organisms in the probiotic should be those normally found in the intestinal tract of a healthy horse. Lactobacillus are the predominant strain in horses.

Second, the cultures of those organisms must be present in a useful form and in a large enough quantity to achieve the desired results. The critical factor to consider is the number of colony-forming units per dose. Winters said the way to evaluate the cost effectiveness of any system--there are several makers of probiotic products--is to evaluate the cost per colony forming unit rather than the cost per pound or by volume.

The third factor Montes and Pugh cited was that, once administered, the bacteria must become active quickly to produce the beneficial lactic acid. In some cases, managers have combined administration of probiotics with substances that assist bacterial growth, such as fermentable sugar, yeast extract, peptides, buffers, and trace minerals.

Probiotics are generally available in two forms: powder and gel. The powder, which Winters estimates costs about 23 cents a day at retail prices, is administered by topdressing it over the horse's regular feed. The gel, which is more costly, can be used for foals which are less adept at feeding or mature horses which have stopped eating.

Winters, who has been giving every horse under his management probiotics every day for four years, contends the cost of the probiotics is made up in reduced feed costs, which is a result of more efficient digestion.

Winters believes that, despite some skepticism over the efficacy of probiotics, they will come into common use among equine managers in coming years.

"I predict that within ten years, 75-80% of horses on well-managed farms will be using these products," he said.

About the Author

Jacalyn Carfagno

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