The horse’s fermentation-focused digestive system enables him to process and utilize forages. It’s essential that the microbial population of the hindgut be healthy, with appropriate numbers of helpful bacteria, protozoa and fungi. The young foal picks up the necessary microbes by eating some of his dam’s fresh manure.
“It’s all too easy to disrupt the hindgut,” says Amy Gill (equine nutritionist). “An abrupt change in feed, or any kind of stress can disrupt the gut. A high-grain, low-fiber diet is also very hard on the microbes and has more negative impact than anything else,” she says.
Many horsemen feed commercial supplements or feeds containing some of the essential microbes. The use of products called probiotics began several decades ago, in attempts to replace normal gut flora after an animal had been sick (and not eating) or was given oral antibiotics that destroyed some of the good bacteria along with the bad ones.
At first, veterinary clinics collected manure from healthy horses, strained it to get some of the juice containing the ‘good’ microbes, and dosed recovering horses with the juices—to re-establish microbe populations that had been decimated by antibiotics. Later the desired microbes were cultured and grown, added to commercial paste products. Various bacterial and yeast cultures were designed to repopulate the hindgut.
Now we have multiple probiotic and prebiotic products that can stabilize the good microbes. They’ve also been shown to have some effect in guarding against harmful bacteria, to help maintain normal gut function. Yeast cultures help select against bacteria that produce lactic acid, and also stimulate the use of lactic acid and fiber. This can prevent some of the pH drop in the hindgut that can lead to colic and laminitis.
Today probiotics are also added to commercial feed mixes. Feed companies have tested their ability to withstand heat in the manufacturing process and have looked at the microbes’ ability to get to the hindgut. They have to survive the trip through the stomach and small intestine.
Recent research at the University of Georgia looked at growth of various strains of pathogenic bacteria in a test tube—to see if adding probiotics would decrease the growth of pathogenic organisms. The tests showed that probiotics must be specific to the equine body in order to be effective. You can’t just expect a generic form of a certain probiotic microbe to help. It must be one that is normally found in the equine digestive tract. Not all probiotics are created equal. What works for a dairy goat or a cow may not work as effectively for a horse.
Since these are living organisms, some people ask about shelf life of the product, and whether the microbes actually make it to the hindgut when fed—whether they can withstand the digestive process while going through the first part of the tract. Gill is currently working with a veterinarian to produce an equine-origin probiotic.
“I’ve learned that most probiotic products on the market today are bovine, and cattle digest forage in the rumen—the first stomach. Unless a product complements what’s in the horse’s digestive tract (and not a cow’s digestive tract) and are alive, they don’t work. Most equine probiotics are not packaged properly to keep them alive while sitting on the shelf at the tack store. Putting probiotic in feed and then pelleting it is also useless because heat from the pelleting process kills it. Heat and light are very damaging to probiotics,” she says. “We’ll be packaging our product in daily doses—in airtight packets, like the individual packets of yeast used when baking. This way, the microbes stay alive and fresh until you actually use them,” says Gill.
Prebiotics are a newer concept in supplements. These are not microbes, but ingredients aimed at helping keep microbial populations in the hindgut stable and healthy. They feed and maintain the microbes. Prebiotics are indigestible sugars that make their way through the digestive tract, stimulating growth of beneficial bacteria. Some of them trick bad bacteria into binding to them. They are excreted in manure, taking the bad bacteria with them.
