Feeding Myths Debunked, Part I. By Lori K. Warren, Ph.D., P.A.S.

Transcription

1 HORSE HEALTH Feeding Myths Debunked, Part I Alfalfa and Protein By Lori K. Warren, Ph.D., P.A.S. PHOTO: ANTHEA MACLAUCHLIN Horses with high protein and mineral requirements, such as growing horses and lactating mares, can benefit from receiving alfalfa. There seem to be more myths and old wives tales about feeding horses than with other livestock. Many of these myths are long-held traditions that have been passed down unquestioned from horseman to horseman, but some are based on fear of causing harm to the horse due to a lack of understanding of either the feed or how the horse may digest it. Over the past 30 years, many myths associated with the feeding of horses have been debunked through scientific study. And yet, rumours still circulate. The purpose of this article is to set the record straight! For horse owners, alfalfa is probably the most misunderstood feed. A perennial legume plant in the pea family, alfalfa is an important forage crop for cattle. Perhaps this explains why there are so many wives tales surrounding the feeding of alfalfa to horses. MYTH: You should never give a horse straight alfalfa. Never say never. In California and the southwest United States, horses are routinely fed straight alfalfa as the only forage. In that region, alfalfa is cheap, plentiful, and the horses do quite well. While some horses may not need alfalfa, others would truly benefit from receiving it. The difference lies in what nutrients alfalfa provides and what the horse actually needs. Alfalfa contains more energy, protein, and calcium than most grass hays (Table 1). This nutrient profile makes it most suitable for young, growing horses and lactating mares, because they have high protein and mineral requirements (Table 2). By comparison, alfalfa exceeds the protein requirements of idle horses and performance horses (Table 2). That does not mean these horses cannot receive straight alfalfa. It just means alfalfa provides more protein than these classes of horses need. Alfalfa also tastes good, so it s useful when you ve got a finicky eater or a horse with a poor appetite. While alfalfa is more nutrient-rich than most other forages, it is not any richer than many other feeds commonly used for horses. For example, good quality pasture is often higher in calories and protein than alfalfa hay (Table 1). Leafy, rapidly growing spring pasture grass may contain 20 to 26 percent protein. By comparison, midmaturity alfalfa hay will contain 16 to 18 percent protein. MYTH: Straight alfalfa should not be fed to young, growing horses. Foals do not have the same capacity as adult horses to house and digest lots of Canadian Horse Journal. Reproduction in whole or in part without the written permission of the publisher is strictly prohibited. 1

2 PHOTO: CHRISTINAHANDLEYSTOCK.COM mature forage in an effort to obtain the nutrition they need for growth. Foals have greater nutrient needs than adult horses, but their digestive systems are only onethird as big. As a result, growing horses need a nutrient dense diet lots of nutrition in a small package. Alfalfa can help meet their high energy, protein, and calcium needs without having to add a lot of extra bulk to the diet (Table 3). High protein does not cause developmental orthopedic disease (more on that later), nor does high calcium. Furthermore, we can adjust the high calcium-to-phosphorus ratio in alfalfa with a suitable mineral supplement. MYTH: Straight alfalfa causes colic and founder. Very few people who circulate this myth have ever actually experienced these problems themselves. And since most people don t want to risk their horse developing colic or laminitis, this rumour has stuck. I m not saying it couldn t happen (never say never). Some horses may be predisposed to colic and founder, particularly obese horses and fat ponies. For easy keepers, alfalfa may be too much of a good thing and is probably better avoided. However, most feed-related cases of colic or laminitis tend to result from feeding grain, alfalfa, or other feeds incorrectly. Because it is richer in energy and protein, alfalfa should be limit-fed, or fed in a fixed amount, rather than offered free-choice. Horses that are fed too much alfalfa or allowed to eat as much as they want often relish the forage so much they will become obese. And obesity is certainly a predisposing factor for colic and laminitis. Because alfalfa has a higher nutrient value, less alfalfa hay will be needed to meet the horse s requirements compared to the amount of grass hay needed. For example, a mature, 1,100 pound horse used for light work will only need 16 pounds of alfalfa each day, but would need 22 pounds of timothy hay to meet dietary requirements. TABLE 1 Comparison of the nutrients in alfalfa with other forages.* Forage Energy Protein Calcium (Mcal/kg) (%) (%) Alfalfa Timothy Brome grass Spring pasture TABLE 2 Alfalfa is a legume plant in the pea family. It can be fed to horses as the only forage source, but should be limit-fed in a fixed amount due to its high nutrient profile. Comparison of the nutrients in alfalfa with the nutrient requirements of different classes of horses.* Requirement Energy Protein Calcium (Mcal/kg) (%) (%) Alfalfa Weanling Yearling Broodmare Idle Horse Performance Canadian Horse Journal. Reproduction in whole or in part without the written permission of the publisher is strictly prohibited.

3 Risk of colic or laminitis also increases when people switch from a mature grass hay to a good alfalfa hay without giving the horse time to adjust to the diet change. The microorganisms in the horse s digestive tract need time to adjust to new feeds, particularly when going from a low quality feed to a higher quality feed. So, if you are switching to straight alfalfa hay, adjust the horse to alfalfa gradually over a period of one to two weeks (each day or two, replace more of the old hay with the alfalfa). Remember you will be feeding a fixed amount of alfalfa, probably less than the amount of hay than you were feeding before. The same is true for grazing a horse on an alfalfa pasture. Horses can safely graze on an alfalfa stand if given time to adjust to the forage. Start with two to four hours of grazing and gradually build up the turnout time over one to two weeks. Keep in mind that mature horses may not need to graze 24 hours per day to obtain all the nutrients they need if the pasture is of high quality. To make better use of your pasture and to avoid obesity, consider restricting grazing time. MYTH: Alfalfa causes bloat in horses. Alfalfa (or any legume) can cause bloat in cattle and other ruminants, and presumably that s where this myth began. As cattle digest forages, the microorganisms in their rumen naturally produce gas. In most cases, cattle eliminate this gas by burping up cud for re-chewing (the process of rumination). When cattle graze lush pastures full of clover and alfalfa, froth develops, trapping the gas in the rumen, thereby leading to a bloated appearance. In contrast, horses do not develop bloat when grazing alfalfa because of the layout of their digestive tract. The alfalfa must first pass through the horse s stomach and small intestine before it undergoes microbial digestion in the large intestine. Because significant digestion of alfalfa takes place in the stomach and small intestine, there is less of a chance for gas to become trapped in the large intestine and to cause bloat. As mentioned earlier, gradually adapting horses to pastures with alfalfa will help prevent many problems. MYTH: Alfalfa causes kidney damage. Although alfalfa may provide more protein than mature horses need, there is no evidence to suggest that a moderate dietary A diet with too much energy, not protein, can make a horse hot. All diets should be balanced to meet, but not exceed, the nutrient requirements of each individual horse to avoid problems. PHOTO: ROBIN DUNCAN PHOTOGRAPHY Canadian Horse Journal. Reproduction in whole or in part without the written permission of the publisher is strictly prohibited. 3

4 excess of protein is detrimental to healthy horses. Protein is made up of amino acids, which are composed of carbon, hydrogen, oxygen, and nitrogen. When horses (or humans) consume more protein than they need, the carbon, hydrogen, and oxygen from the amino acids are used for energy and the excess nitrogen is excreted in the urine. Horses consuming alfalfa (and other high protein feeds) have been noted to drink more often and urinate more than horses consuming lower protein diets, but there is no reason to believe that a horse s kidneys will be damaged when this occurs. It s only when a horse already has pre-existing kidney disease that the high calcium and protein in alfalfa can aggravate kidney dysfunction. When feeding alfalfa, it is important to provide free choice access to water to ensure the horse can flush the excess nitrogen from its body. When alfalfa-fed horses receive restricted access or limited amounts of water, they often produce more concentrated, brown, thick urine. MYTH: High protein feeds make my horse too high spirited. The belief that behaviour can be affected by feeding hays or grain mixes with a high protein content is probably one of the most common misconceptions among horsemen. There is no data, either scientific or otherwise, which suggests that protein intake has anything to do with mental attitude. However, high-spirited behaviour has been directly linked to the energy content of the diet. The horse is unique in that it compensates for excess dietary energy by increasing physical activity. As a result, the horse that receives too much energy (calories) in the diet is more apt to be excessively high spirited and buck, shy, or run away. To gain a better understanding, the horse owner must be able to differentiate between the energy and the protein content of the diet. High protein does not necessarily mean high energy, and vice versa. Grains have 30 to 50 percent more energy than hays, but not necessarily more protein (Table 3). Overactive behaviour might result if the horse is receiving more grain than is needed or if you have switched to another type of grain that contains more energy. For example, on a pound-for-pound basis, corn and wheat contain ten percent more digestible energy than oats, but they aren t necessarily higher in protein (Table 3). Furthermore, corn and wheat are more energy dense (heavier bushel weight), so these grains provide twice as much energy as an equal volume of oats. If you were feeding a coffee can of oats and you switched to corn, you would only need to feed half a can to provide the same amount of calories. If you TABLE 3 Comparison of the energy and protein content of common grains and hays fed to horses.* Feed Energy Protein (Mcal/kg) (%) Wheat Corn Barley Oats Alfalfa hay Brome grass hay Timothy hay TABLE 4 stayed with a whole can of corn, you would be excess dietary energy, particularly if they are Comparison of the energy and protein requirements for different classes of horses with a mature weight of 1100 pounds (500 kg).* Horse Energy Protein (Mcal/kg) (%) Idle Horse Weanling Yearling Broodmare Light Work Moderate Work Intense Work providing your horse twice as much energy. The same is true for some grain mixes: some sweet feeds and pellets may contain a higher proportion of corn, wheat, or barley, and some contain added fats or oils, all of which have more energy per pound than oats. Beyond the grain source, too much energy can also come from hay. Alfalfa, although high in protein, is also higher in energy than most grass hays like timothy (Table 3). If the amount of alfalfa fed supplies more calories than the horse needs, it is the energy content of the alfalfa, not the protein content, causing his hyper behaviour. The bottom line: too much energy in the diet (excess calories) equals too much energy in the horse (hyper behaviour). Protein level has nothing to do with it. Remember that horses are individuals. Some horses are more high-strung than others and will feel the need to burn off confined to a stall for most of the day. Other horses demonstrate the opposite effect with excess calories they become fat and lazy. Keep in mind that the diet may not be to blame. Maybe the horse needs additional training to become more manageable or perhaps the horse is experiencing some type of pain or discomfort. MYTH: Performance horses need a high protein diet. Several surveys conducted on feeding practices have revealed that mature performance horses receive two to three times as much protein in their diet as they require. The common belief that once a horse s activity substantially increases through training, riding, or showing extensively, he needs more protein in his diet is false. This myth likely has its roots in human nutrition. For hundreds of years, it was 4 Canadian Horse Journal. Reproduction in whole or in part without the written permission of the publisher is strictly prohibited.

5 PHOTO: ROBIN DUNCAN PHOTOGRAPHY consistently is energy, the calorie content of the diet. When a horse (or human) is exercising, the muscles doing the work are burning lots of calories. So, it should make sense that we need to provide more calories in the diet of a working horse to compensate for all the extra calories he expends when being ridden or worked. As the level of activity increases (either by speed or distance), the requirements for energy increase proportionally (Table 4). For light riding a few times a week, the horse s energy requirements increase approximately 25 percent over that needed by an idle horse. For moderate work, such as barrel racing, jumping, team penning, and cutting, energy requirements may increase by 50 percent. For intense work, such as racing and endurance riding, energy requirements can increase by more than 100 percent over those of the idle horse. Therefore, while protein needs do increase slightly with exercise (two to three percent), energy needs increase dramatically (25 to 100 percent). In most cases, we can meet the increased protein needs of performance horses when we adjust the diet to provide for the increased energy needs. Good quality pasture and lush spring grass are often higher in calories and protein than alfalfa hay. believed that exercise and training involved the tearing down of old muscle and the building of new muscle. Since muscle is primarily composed of protein, it was deduced that more protein is needed in the diet of human athletes to serve as the building blocks for new muscle. A significant amount of both human and equine research over the last 50 years has disproved this theory. But both human athletes (the prime example being body builders) and horse owners have been slow to catch on. I do not deny that protein needs increase with training and exercise, because they do (Table 4). However, protein needs do not increase greatly with exercise, particularly when you compare the protein needs of a working horse to a young, growing horse, or a broodmare (Table 4). The nutrient affected most when a horse enters training or is being ridden MYTH: High protein diets cause development problems in foals. Genetics, exercise, and nutrition all play a role in the development of healthy bones and, as a result, the same factors are also linked to the occurrence of developmental orthopedic disease (DOD) in young horses. Most confusion regarding DOD is related to nutrition. Mineral imbalances have been well-documented as a cause of DOD. Excessive protein was blamed as a cause in the 1970s, but later studies disproved this connection. Feeding more protein than the foal needs does not increase growth rate above that achieved when the diet just meets protein requirements. Unfortunately, the diets of many young horses are kept quite low in protein for fear of causing developmental problems. Restricting protein will not result in improved bone growth and can actually be harmful to the foal by decreasing feed intake, growth rate, and skeletal development. On the other hand, overfeeding energy will result in developmental problems, particularly if protein and mineral intake are not increased at the same time. Again, the horse owner must be able to differentiate between the energy and the protein content of the diet. For growing horses, protein and minerals must be in proportion to the energy in the diet. b Horse Feeding Myths, continues in the February issue with Bran, Beet Pulp, Grains, and more. Reprinted with permission from Alberta Agriculture. Canadian Horse Journal. Reproduction in whole or in part without the written permission of the publisher is strictly prohibited. This article is provided courtesy of... Every issue is packed with expert advice and information for all breeds and disciplines, on a broad range of topics to appeal to all levels of horse experience. Subscriptions include both the print and digital editions. TO SUBSCRIBE VISIT subscriptions@horsejournals.com CALL , ext 212 5