Feeding Horses Cattle Feed: Just Ruminating

Ever had your feed store deliver a bag of cattle feed to your farm by mistake? If you opened that bag, you probably noticed, on first inspection, that the mix inside looked a whole lot like the sweet feed you thought you'd ordered. Corn, barley, oats, molasses--all the basic ingredients are the same, and even the protein level might not differ that much from what you normally feed your equines. You might start to wonder whether the differences between cattle and horse feeds are really significant at all.

In fact, across North America, some horse people do routinely feed their horses bovine rations, either because it's convenient (as it might be if you're also raising dairy or beef cattle) or because, in many instances, it's quite a bit cheaper. But is this really a good idea?

In truth, it's not--for several reasons. On the surface, cattle feeds might look like an appropriate choice for your horses, but nutritionally, there are a number of important differences. Cats and dogs might appear to have similar nutrient requirements, but, in reality, need very different diets (cats have a specific requirement for the amino acid called taurine, for example, that generally is not added to dog foods). This is true also with cattle and horses. They have major digestive and metabolic differences that make their dietary needs quite diverse.

The Tummy Tour

From an evolutionary standpoint, cattle have very evolved and efficient digestive systems. In that regard, cows leave horses in the proverbial dust. Although both species depend on forage materials for the bulk of their nutrition, they've developed very different techniques to process their fiber.

Cattle, as most of us know, have four-compartmented forestomachs, consisting of a rumen, a reticulum, an omasum, and an abomasum (the true stomach). Briefly, fiber fermentation (digestion) begins in the rumen and reticulum, when the gut microbes go to work to break down the tough cellulose chains of the plants. Food that initially enters the rumen is later regurgitated and re-chewed (the familiar act of "chewing cud") to help break down tough plant fibers further. When the cud is swallowed, it ends up in the fermentation vat of the rumen (which can hold 40 to 60 gallons of material and might take up nearly the entire left side of a cow's abdominal cavity). Both the rechewing and microbial fermentation in the rumen break the feed particles into smaller and smaller fragments. When the particles are a certain size, they are passed onto the reticulum and then the omasum for further processing, then finally to the abomasum for the beginning of enzymatic digestion. A by-product of the initial bacterial/protozoal digestion is volatile fatty acids, or VFAs, which are absorbed through the rumen wall into the cow's bloodstream and can be used as an energy source.

As the fiber moves through the cow's digestive tract, her system efficiently extracts nutrients. In the omasum, particles of food are broken down and made smaller, and water is resorbed from the digestive liquid. As the feed hits the abomasum, hydrochloric acid begins the second phase of chemical digestion. Enzymes secreted in the small intestine do much of the remaining digestive work and allow nutrients such as amino acids (the building blocks of protein) to be absorbed into the system across the small intestine's wall. This also is where carbohydrates and fats from grain rations are broken down if not fermented in the rumen.

As the feed arrives in the cecum, any fiber that previously was not digested is now fermented in a process similar to that found in the rumen, meaning that cows (and other ruminants) have two shots at thoroughly digesting the fiber they take in. This, in part, explains why cattle can manage to extract more nutrition from poorer feedstuffs than horses extract.

Finally, the large intestine completes the job of fiber and carbohydrate digestion, and also retrieves more water from the mix. What's left forms feces, which pass out through the rectum.

Horses, in contrast, approach fiber digestion in reverse order. Hydrochloric acid in the horse's single stomach kickstarts the process of chemical digestion of protein, fats, and carbohydrates. That continues in the small intestine, where enzymes break down the non-fibrous nutrients into their subunits (amino acids, simple sugars, and long chain fatty acids) which are efficiently absorbed before reaching the cecum. However, fiber digestion doesn't really take place until the feed moves into the cecum, where the gut microbes reside. The horse's cecum is unusually large to accommodate its high fiber intake. Fermentation is initiated in the cecum and continues throughout the four compartments of the enormous large colons. Volatile fatty acids, some microbial amino acids, and phosphorus are efficiently absorbed by the large colon mucosa. Finally, in the small colon, much of the water in the mix is resorbed, and what's left over (undigested) is expelled as manure.

Because cattle have so many "back-up" systems in place to extract every conceivable nutrient from their feed, they can, in the words of one pundit, turn garbage into gold. In other words, they don't necessarily need high-quality food in order to thrive; they can make the most out of "kitchen scraps" or virtually anything vegetative that comes within range of their big, blunt teeth.  Furthermore, their systems are far more talented than a horse's at manufacturing their own amino acids.

"Cattle can produce many of the amino acids they need microbially," says Lori Rice, PhD, an equine and ruminant nutritionist at the University of Florida. "In comparison, horses absorb most of their nutrients in the small intestine, before the main fermentative section of the digestive system, so the contribution of the gut microbial population is small. As a result, horses have a need for much better quality protein than cattle."

Cattle also have the ability to synthesize protein from a number of different sources besides dietary plant proteins. For example, they can process urea, an inexpensive nitrogen source, and turn it into useful amino acids. Horses can utilize some urea and actually are more resistant to urea toxicity than are  ruminants.

Rice explains another of the important differences between bovine and equine digestive systems. "In terms of fiber digestion," she says, "the location of the fermentative "vat" is important." In cattle, fiber fermentation comes first, and is much more thorough, "which is why cattle can eat almost any cellulose source, even the toughest and most fibrous, while horses (whose fiber fermentation process comes after other nutrients are absorbed) need good-quality forage.

"On the other hand, cattle and horses are alike in that they both need roughage to maintain the health of their digestive tracts," she adds. "The very act of ruminating allows cattle to digest fiber with higher lignin content." Lignin is a type of fiber that is very tough and strong; the more lignin, the harder the plant material. A young grass stalk, for example, is low in lignin, while an oak tree has a high lignin content. The higher the lignin content, the less actual digestible fiber is present; therefore, the higher efficiency in digesting cellulose allows the cattle to derive more from poor quality forages.

The horse's need for higher-quality forage also explains his "pick and choose" method of grazing (vs. the cow's "lawn-mower approach).

According to Rice, another pivotal factor in fiber digestion for cattle is the length of the individual fibers; they should be no shorter than an inch in length, and preferably at least three inches long. Shorter fiber pieces (such as might be found in hay cubes or pellets) can contribute to digestive upset. The same isn't necessarily true for horses, who seem to handle longer or shorter fiber pieces equally well, assuming the horse's teeth are in good shape and the feeds are introduced slowly. However, unlike with ruminants, the pelleted forages especially appear to not provide enough "chew time" for horses, resulting in an increased amount of wood- chewing activity if cubed or pelleted feeds are the major or only source of fiber.

Quite apart from the contrasts in their digestive systems, the whole way in which we feed cattle and horses is different, Rice points out. The success of a bovine diet can be quantifiably measured, either in terms of weight gain (for beef cattle) or milk production (for dairy). Feeding horses is considerably more nebulous; we have to base our assessment of a diet's success on hard-to-define qualities like the shininess of the animal's coat, his performance under saddle or in harness, his response to a conditioning program, the amount of weight he carries, and his general attitude. Feeding cattle can be categorized as a science, while feeding horses depends more on (if you'll pardon the expression) gut instinct.

Small Differences, Big Impact

The digestive design differences between cattle and horses mean that, while both are grazing animals, they have very dissimilar nutritional needs. Those differences are reflected in the grain rations commercially available to cattle and horse farmers. The feeds might look the same, but beneath the surface there's not much similarity other than the presence of the common grains.

Cattle are requested only to eat and grow or produce milk, whereas horses are asked to perform athletically which increases their need for some B-vitamins, perhaps vitamin E, and maybe C. These vitamins are synthesized in the liver of both species but depleted during prolonged stress in the horse. The increased minerals in horse rations reflect the horses' ability to lose electrolytes through sweat, which cattle do not do. In an average cattle feed, vitamin and mineral supplementation tends to be minimal for these reasons.

Although most commercial cattle rations in North America contain the same grains we're used to seeing in horse feeds--oats, corn, and barley--the quality of those grains might not be up to par for your tastes, or your horse's. Cattle are far less fussy eaters than horses, and cattle farmers, for the most part, are less fussy consumers. They aren't concerned about the presence of foreign objects (weed seeds, rocks, sticks and branches, lumps of dirt, or fillers like ground corn cobs or seed hulls), dust, or fines (small particles) in the feed. A bag of 16% protein beef cattle feed I recently sifted through contained all of the above, plus a Canadian penny!

Fat is another ingredient that can be utilized by both cattle and horses in about the same quantities (averaging 5%-7% of the total diet). In cattle feeds, fat most likely is supplemented in rations designed for high-producing dairy cows that have high energy needs and sometimes lose weight while lactating, but because rumen bacteria can�t tolerate high fat levels, some cattle feeds contain a special "rumen protectant" or "rumen inert" variety of fat (composed of hydrogenated tallow, or the calcium salts of fatty acids). That, at best, is fairly indigestible to horses, and, at worst, might be toxic. More commonly, cattle feeds might contain whole cottonseed or full-fat whole soybeans as fat sources. Whole, unprocessed oilseeds contain substances, such as goosypol in cottonseeds, that are toxic or that inhibit protein digestion. These substances are rapidly broken down by microbial fermentation, and, therefore, are quickly neutralized in the rumen. Since fermentation occurs only in the hindgut of horses, the substances are unaltered during the enzymatic processes in the small intestine and can wreak havoc.

Crude protein levels in some cattle feeds might seem appropriate for horses at first glance. Most feeds designed for adult beef cattle or milking dairy cattle contain about 16% crude protein, which is appropriate for a growing foal or a lactating broodmare; and "dry and finishing" feeds, for dry cows, tend to be in the 12% crude protein range, which is more suitable for a mature horse. However, a large portion of this "protein" might be in the form of urea and as mentioned above, horses aren't as good at utilizing this "nitrogen" source as the ruminants. Therefore, the actual available protein and amino acid content of the feed might be substandard for horses, especially growing foals and lactating mares.

The Lethal Lunch

There's another danger involved with cattle feeds, however, that is even more alarming. That's the presence of anti-coccidial medications called ionophores such as monensin sodium (trade name Rumensin, Lasalocid, and Naracin). Those medications are added to many cattle feeds (generally those designed for beef cattle) to aid feed conversion and weight gain under stressful conditions, such as a crowded feedlot. Many ruminants benefit from drugs like Rumensin, and similar medications are added to many poultry feeds; however, anti-coccidial medications are extremely toxic to horses, often proving fatal, even in minute doses. In one study, doses of monensin of only 1.0 to 3.0 mg per kilogram of equine body weight were enough to kill more than 50% of the horses to which they were administered. Death came after 12 to 36 hours of progressive weakness (especially in the hindquarters), incoordination, disorientation, colic, labored breathing, and profuse sweating. In horses which recover from Rumensin poisoning, there can be long-standing cardiac degeneration, unthriftiness, and poor performance, with the possibility of delayed cardiac circulatory failure. The levels present in cattle feeds are toxic to horses.

Cattle feeds that are medicated with anti-coccidial drugs must be labeled as such, but the labeling hardly jumps right out at you. You'll have to look carefully at the feed tag to ascertain whether the feed contains one of these dangerous medications. It's also important to note that just the residue of Rumensin on a poly feed bag that previously contained a medicated feed can be enough to poison the feed you buy. That's why it's never a good idea to recycle feed bags, however ecologically correct the practice might appear.

Most feed mills are aware of the danger Rumensin presents to horses, but some are more careful than others. It's a good idea to find out whether your feed mill manufactures any medicated feeds, and if so, how thorough its procedures are in cleaning all of its equipment before it makes a batch of horse feed or non-medicated cattle feed. Ideally, you should only buy your horse's feed from a mill that doesn't manufacture any medicated feed. Make sure your feed mill keeps medicated feeds in a completely separate area from the feed you're buying for horses, and that it never ships the two types in the same truck.

Should You Feed Cattle Rations?

The short answer: Your horse might survive on a non-medicated cattle feed, but he might not thrive. While he might be able to extract enough energy from such a feed to provide for his minimum energy needs, he might be lacking in quality protein and (if stressed) some vitamins, unless you are prepared to do some fancy calculating and provide him with protein vitamin/mineral supplementation over and above what little is in the grain. A horse on lush pasture will tolerate the lower levels of nutrition in a cattle feed better than will a horse on poor pasture or late-cut hay, but in most cases, what's lacking in a bovine feed eventually will catch up with your horse, making the little bit of money you save in buying it a false economy in the long run.

About the Author

Karen Briggs

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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