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Feeding to minimize chronic colic

Posted: Saturday, May 18, 2002

Good feeding practices and attention to special nutrition needs can help horses prone to colic

Repeated bouts of colic are a frustrating management problem and, according to one survey, Thoroughbred owners have more problems with colic than owners of other breeds.

From spring 1998 through spring 1999, the United States Department of Agriculture's National Animal Health Monitoring System (NAHMS) Equine '98 epidemiologic study monitored 1,026 horse operations (each with three or more horses) in 28 states for colic. NAHMS Equine '98 found that 10.9% of Thoroughbreds (the study did not include horses at racetracks) colicked during the study period compared to 4% of the general horse population. This study did not find any correlation between gender or use and colic. By age, foals were the least likely horses to colic. Among other age groups, horses age 18 months to five years were slightly more prone to colic than other age groups.

After old age, NAHMS Equine '98 found that colic was the leading cause of equine deaths (18%). That was no surprise to horsemen who know too well that death is always a potential threat when a horse colics. Frequent emergency veterinary visits for colic can drain a farm's bottom line. When the animal is a particularly valuable stallion or broodmare, its loss can be a definite blow to the farm's financial future. So farm managers look for every possible way to prevent, minimize, or at least anticipate bouts of colic.

Good feeding practices and attention to the individual horse's special nutrition needs are among the principal steps that farm managers can take to deal with horses prone to colic. However, while some prevention practices fall within a farm staff's control, many cases of colic result from health issues that have little or nothing to do with the horse's day-to-day handling (see sidebar, "How do horses colic?"). A horse may never have a bout of colic until a separate health crisis somehow compromises its gut function and sets the animal up for recurring problems.

A change in diet or feeding schedule that may mildly affect the typical horse can be life threatening to the horse with a sensitive digestive tract. The feeding practices outlined below certainly apply as much to healthy horses as they do to those prone to colic. However, they bear review since they can be critical for the colic-prone horse. The farm manager, veterinarian, and nutritionist should work as a team to identify any management events or feeding practices that appear to trigger bouts of colic in an individual horse (see sidebar, "More ways to cope"). Then they can develop a customized feeding and management program to help the individual horse eliminate or minimize gastric distress.

Colic prevention 101

Horse owners most commonly blamed unknown causes for colic in the NAHMS Equine '98 study. Gas colic and feed-related colic were the second-highest types reported, both of which have causes that careful attention to nutrition and feeding practices can minimize.

A change of diet in the two weeks preceding the episode, particularly a change of hay, was the most likely cause of colic cited by 145 veterinarians reporting on more than 1,000 horses that colicked in a 1997-'98 Texas survey of dietary and other management factors associated with colic. Not surprisingly, the Texas study found that a previous history of colic, especially abdominal surgery for colic, predisposed horses to further episodes.

Weather changes during the three days prior to the colic episode, a recent change in stabling, poor or erratic parasite control, or administration of a deworming product during the seven days prior to the colic episode were also identified as factors associated with an increased risk of colic. Horses that were pastured with free access to a plentiful water source, stalled less than half the time, and received no exercise other than ambling around their pasture had a much lower risk of colic.

Working from 1992-'94 with a much smaller population of horses than the NAHMS or Texas surveys, the Michigan Equine Monitoring System tried to identify colic risk factors among that state's equines. MEMS found that geldings were less likely to colic than mares, while broodmares were 2.5 times more likely to develop colic than other horses. Older horses were more likely to colic than younger ones; horses that were competing were more likely to colic than those that were not; and horses with ready access to adequate water supplies were less likely to colic than horses without that access.

These surveys confirm many of the management practices and feeding recommendations that veterinarians and nutritionists have made for years to decrease the chances of digestive problems. The more of these farm managers can put into practice, the more they can help the horses with chronic colic problems.

1. Make any dietary change as gradually as possible. The biggest surprise in the Texas survey was that a recent change in hay gave a horse higher odds of developing colic than any other factor.

Farm managers have long recognized that changes in the quantity or type of a horse's concentrate ration need to be done gradually in order to avoid digestive upset. But when it comes to hay they figure, well, hay is hay.

This study, however, confirmed that a change in the quantity, type, or quality of forage in the horse's diet needs to be made with just as much care. Various types of forage or different cuttings even from the same field are nutritionally distinct and are not interchangeable in the horse's diet. Changing forage sources may change the gut's pH and force adjustments in the population of microflora essential for processing roughage that colonize the horse's large intestine. Making an abrupt change in hay supplies can cause colic as easily as an abrupt change in grain or supplements.

When a horse prone to colic needs to leave the farm for breeding or other travel, send as much of its current hay and grain ration along as is practical so that changes to new feedstuffs can be made as gradually as possible.

2. Emphasize roughage as much as possible. Speaking of hay and forage, the closer it is to 100% of the colic-prone horse's diet (assuming the horse has not had a bowel resection), the better off the animal will be. The horse's digestive tract is designed to extract energy as volatile fatty acids from fiber-rich roughages such as grasses and legumes via fermentation in its hindgut. While racehorses may need as much as 50% of their total ration as carbohydrate-rich grains to have sufficient energy for their work, the colic-prone horse generally does best when grain is minimized or even eliminated from its diet.

3. Feed hay before grain. Horsemen have long feared the consequences when a horse finds a way to gorge on grain. They may be less aware, however, that when horses eat hay right after a large grain meal, they may be setting themselves up for exactly the same problem.

If the bulky forage pushes undigested grain (carbohydrates) into the hindgut, it upsets the gut pH the same way as when a horse stuffs himself on grain. As the gut pH changes and becomes more alkaline, some of the bacteria living there die. The balance between good and bad bacteria in the microflora begins shifting. The result may be diarrhea, gaseous colic, laminitis, enteritis, or other health crises. The higher the proportion of grain to hay in the horse's total diet, the more likely this problem is to occur.

Feeding at least a portion of hay before feeding any grain can reduce the likelihood that undigested grain will get pushed through the stomach and small intestine too quickly. It may also help reduce the tendency of some horses to bolt their feed, another factor that can increase the risk of colic. Reducing the amount of grain fed is an even better solution.

4. Feed many small meals rather than two larger meals. Another solution to the problem of undigested grain reaching the hindgut is to split the horse's daily ration into several meals. Horses have a relatively small stomach, so several small meals spread out over the course of the day are easier on the colic-prone horse's digestive tract than a large breakfast and dinner, especially if those meals are heavy on grain. Keeping the horse's intestinal tract more or less continuously full may minimize the potential for intestinal twists.

Depriving the horse of food for more than 12 hours can lead to irritation of the intestinal lining. As the hungry horse begins to anticipate food, the increased secretion of stomach acids and bile lowers the gut pH. These gastric juices begin to eat away at the intestinal lining, which can lead to ulcers. The horse's irritability and pain in the early stages of this ulceration process is sometimes interpreted as colic.

5. Substitute fat-based energy sources for carbohydrate-rich energy sources. One way to reduce the amount of carbohydrate-rich grain in the horse's diet is to substitute some fat as an energy source. Studies in both Texas and Kentucky have demonstrated not only that horses are able to digest and use the energy in fats, but also that fat energy appears to give them a slight aerobic edge. Since fat contains 2.25 times more energy than carbohydrates or protein, adding 5% to 10% fat to the horse's overall diet allows a farm manager to reduce the amount of grain a horse receives by up to 25%.

A daily feeding of up to one cup of liquid vegetable oil or two pounds of heat-stabilized rice bran will accomplish this, but make the substitution of fat for carbohydrates gradually over a period of several weeks to minimize digestive upset. (Also be sure to rebalance the minerals in the horse's diet, if necessary, when making this switch.) Since fat is easily digested and less likely to add to the gut's acidity than other concentrated energy sources, feeding fat may help horses with ulcers or those that must be on high-concentrate diets.

6. Provide top-quality feedstuffs. This is always a good idea, but farm managers need to be particularly fussy about the quality of the chronic colicker's rations. Buy concentrates from mills that have a regular testing program for mycotoxins that can wreak havoc on the horse's digestive system. Then store and rotate stocks of feedstuffs to minimize the possibility of spoilage.

While whole, unprocessed grains have a long shelf life, do not store processed feeds for more than three months during cooler winter months and for more than a few weeks in hot, humid weather. Avoid less digestible, stemmy, poor-quality hay, which can contribute to impaction colic. Seek hay dealers who contract with producers who take measures to keep weeds out of their fields and who use cutting and conditioning practices that minimize the potential for mold or blister beetles.

Use caution when feeding the chronic colicker from round bales. Feeding round bales free choice in pastures increases the potential that the horse with a sensitive gut may ingest moldy hay. Also, the potential for impaction colic increases if a greedy horse eats too much free-choice dry hay without taking enough trips to the water tank.

Although there are no definitive studies on any relationship between different types of hay and the incidence of colic, fewer problems are reported when feeding alfalfa, timothy, orchard grass, and brome than with other hays. The type of hay is probably not as important as its quality. Moldy or dusty hay of any kind may cause health problems. Both overly mature, coarse, fibrous hays and very fine textured hays can contribute to impaction colic when horses do not chew them properly.

7. Feed on a regular schedule or feed on no schedule at all. Reducing the incidence of colic often means reducing stress. When horses are accustomed to a regular feeding schedule and a meal arrives late, the waiting makes them anxious. As stress hormone levels rise and digestive juices begin to flow in anticipation of feeding, the potential for digestive upsets increases.

Feeding schedules often have more to do with human than equine needs. If maintaining a regular feeding schedule is difficult, choose to be consistently inconsistent. As the horses become accustomed to being fed over a range of time rather than at a precise hour, a late meal will not cause anxiety. Feeding smaller amounts at more frequent intervals may also help the horse that stresses over twice-a-day grain rations. For stabled horses, consider automatic feeders that can deliver small amounts of grain or pellets throughout the day.

8. Provide ample turnout and minimize stall time. The Texas study found that horses pastured with free access to a plentiful water source, stalled less than half the time, and receiving no exercise other than ambling around their pasture had a low risk of colic. Provide colic-prone horses with as much turnout time in a large paddock or pasture as possible and minimize stall time. If the horse is overweight, keep pastures clipped short, turn the horse out with a grazing muzzle, or use a large dry lot to control grass intake.

The study findings suggest that colic-prone horses in heavy work may do better with a regular exercise routine. For example, daily gallops may be less likely to set the horse up for colic than a hard workout followed by several days of stall rest. Daily hand walking or time on a hot walker may help some horses. Good record keeping (see sidebar, "More ways to cope with chronic colic") can be an invaluable guide to what works best for an individual horse.

9. Provide a reliable source of clean, drinking water free choice. Horses typically drink six to ten gallons of water daily depending on the temperature, the kind of feedstuffs they are eating (grass is 90% water), and their workload. Stalled horses drink the most water within a few minutes after eating grain or within an hour after eating hay. Without ample water at these critical times, they are at risk for dehydration and impaction colic.

When temperatures drop in the winter, horses tend to drink less, and cases of impaction colic tend to rise as a result. Warming the horse's sole source of water can increase winter water intake. In two Pennsylvania trials during cold weather, ponies drank 40% more heated water than cold water when offered one or the other. When the ponies were given a choice of either warm or cold water, they tended to choose the cold water but they drank much less water than they did when offered warm water alone.

Use buckets rather than automatic waterers to monitor the water consumption of stabled colic-prone horses and keep them filled. Horses that drink insufficient water may be tempted by the addition of fruit-flavored drink mixes, apple juice, or a few drops of peppermint flavoring. Avoid pasturing the colic-prone horse where water sources are difficult to reach or tend to become muddy or scummy, discouraging consumption.

10. Follow a regular parasite prevention program. Parasites have been blamed in many cases of colic. Large masses of roundworms can cause impaction colic. Migrating larvae can damage blood vessels and decrease the blood supply to the gut. They can also block renal or bile ducts. Parasite damage to gut walls makes it harder for the horse's digestive tract to work efficiently, contributing to both colic and malnutrition.

11. Observe animals carefully for several days following administration of any medications, including dewormers. If a heavily parasitized horse is dewormed, there is concern that massive quantities of dead or dying worms may increase the risk of various types of colic. Some dewormers have been implicated in problems, particularly when administered in higher than recommended doses.

Antibiotics can upset the bacterial balance in the hindgut. Long-term use of nonsteroidal anti-inflammatories such as flunixin meglumine (Banamine) or phenylbutazone can damage the intestinal lining, making the horse more prone to colic. Whenever the horse is ill or has received medication of any kind, farm staff should be particularly alert for recurring colic. If possible, keep all other changes in the horse's diet or environment to a minimum.

12. Observe animals carefully during seasonal changes or weather changes. Pastures experience a flush of growth in spring, again in fall, and when rain finally ends a dry spell. At these times, fructan or plant sugars accumulate in the grass in amounts that are similar to those in a starchy, high grain meal. If undigested sugars get pushed into the hindgut, the end result may be colic or laminitis.

Monitor the chronic colicker's grazing carefully at these times. Limit grazing to early morning hours since fructan production increases from midday into the afternoon hours. Colder weather often means decreased water intake and an increased potential for impaction colic. Some researchers feel that any drop in barometric pressure (signaling a weather change) produces lower water intake. Again, if weather or other environmental factors are changing, avoid making other changes that might stress the horse in any way including diet, housing, or exercise.

13. Observe animals carefully when there are major changes in their environment or social units. Stress, again. The colic-prone horse may be more reactive whenever the simplest thing in its environment changes. Loss of a favorite companion to weaning, moving to a new pasture, changing tracks, or changing an exercise routine can set them off. Minimize changes or make them one at a time for the colic-prone horse. Reducing stress also helps reduce the incidence of ulcers, another health factor that increases the likelihood of colic.

14. Keep teeth in good condition. Dental problems can lead to poor chewing. The horse's feed does not get mixed adequately with saliva (which starts the digestive process) before it is swallowed. Inadequately chewed food can cause the horse to choke and is harder for the horse's digestive tract to process, leading to impaction. If the horse's digestive tract has already been compromised by previous bouts of colic or by resectioning, this can be a serious problem.

15. Avoid feeding hay off the ground or turning horses out in overgrazed paddocks, especially on sandy soils. Heavy sand settles onto the bottom of the intestinal tract where it can cause irritation and, eventually, persistent diarrhea or colic. When horses are fed hay on sandy soils, they ingest sand as they scavenge for the last tasty leaf bits. Overgrazing pastures on sandy soil contributes to the same problem.

To check for sand, put a few balls of fresh manure (brush off any adhering dirt) into a quart jar, add three to four times the same volume of water, and shake it into a slurry. Allow the mixture to settle a little, then pour off two-thirds to three-quarters of the water. Repeat the process several times until the water becomes relatively clear, and observe if there is any visible sand at the bottom of the container. A stool sample with visible sand is cause for concern.

16. Consider probiotics for the chronic colicker. Maintaining the microflora, a strong population of the right bacteria in the horse's hindgut, is critical for proper digestion. The ability of an older horse's gut to maintain a good population of bacteria on its own may be compromised. Any kind of stress, from transportation to a change in companions, can upset the pH of the hindgut and kill or stress the bacteria there.

Researchers are divided as to whether adding probiotics (live cultures of beneficial bacteria such as Lactobacillus), yeasts such as Sacchronmyes, or digestive enzymes really benefits the microorganism population in the horse's gut. Proponents maintain that including these beneficial bacteria in the horse's daily feed may give the colic-prone horse some additional help. Farm managers may want to administer live cultures orally as a preventive measure after an event that can stress the gut, such as deworming, antibiotic treatment, or foaling.

Keep in mind, however, that any effect they may have will not be immediate. Beneficial bacteria in the gut double approximately every 30 minutes, so it can take three to 21 days for the population to change and adjust to a new feedstuff or to return to normal levels after an event that decimates their numbers.

How do horses colic?

A wide range of conditions can cause abdominal distress. Management of feeding practices and diet may help in some, but not in all, cases. Nutritional intervention at some level may help prevent or diminish:

• Gas colic
• Sand colic
• Impaction (small or large intestine)
• Enteroliths
• Ulcers
• Grain overload
• Gastric distention (stomach)

Changing the horse's diet or feeding routine is unlikely to have any effect on colic resulting from:

• Parasite damage to intestinal arteries
• Parasite migration
• Drug reactions
• Twisted intestine
• Telescoping intestine
• Hernia
• Twisted uterus
• Intestinal adhesions
• Peritonitis
• Colitis
• Tumors
• Strangulating lipomas (fatty tumors)
• Retained meconium in foals