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| Control Colic Through Management |
KER
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 Colic is one of the most dangerous and costly equine medical problems, estimated to occur in 1 of every 10 horses each year. In recent years, several studies have been published identifying potential causes and risk factors associated with colic in horses. As any equine veterinarian would attest, there seem to be countless situations which can precipitate colic.
Factors which are difficult for horse owners to control include breed and age of horse along with geographic region of the country where the horse is kept. Other factors, including internal parasite control, the quality and quantity of fibre in the diet, and grain feeding management, can be managed to reduce the risk of colic. The following is a discussion of several nutritional aspects of colic which can be managed, thereby reducing the incidence of colic.
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Risk factors for colic
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- Change in diet
- Change in hay type and intake
- Grain intake greater than 2.5 kg per day
- Eating sand
- Spoiled Feed
- Restricted water access
- Change in activity
- Transport
- Change in Housing
- Parasites
- Administration of Wormer
- Previous history of colic
- Breed
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Signs of colic
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The signs of colic are quite variable – remember colic is the term given to any horse showing abdominal pain. Signs depend upon the cause of the colic and are listed in the table below along with the frequency at which particular signs are shown by horses with colic.
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| Signs of Colic |
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| Rolling | 44% |
| Pawing | 43% |
| Lying down | 29% |
| Getting up and down | 21% |
| Flank watching | 14% |
| Lip curling | 13% |
| Backing into corner | 10% |
| Kicking at belly | 7% |
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Internal Parasite Control
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Parasitic load has long been stressed as a potential cause of colic. There are several mechanisms by which internal parasites could cause colic symptoms in horses. Two of the most obvious mechanisms include damage to the blood supply and decreased motility of the digestive system. Uhlinger (1990) has reported the benefits of routine administration of oral anthelmintics to reduce the incidence of colic. Therefore, it is recommended that horses be maintained on a regular internal parasite control program tailored to their individual parasite load.
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Quantity of Fibre
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Anatomically, horses have developed a specialized digestive system which allows them not only to survive, but also to thrive on high fibre diets. The caecum and colon collectively hold approximately 21 to 24 gallons of liquid, and house billions of bacteria and protozoa which produce enzymes that ferment plant fibre. The horse's small, one-compartment stomach stresses the need for a continual intake of feedstuffs. Taken together, a small stomach coupled with the large capacity of the fibre fermenting hindgut make the horse ideally suited to graze.
Pond et al. (1995) reported that horses on pasture graze for up to 17 hours/day and nearly continuously with distinct breaks in grazing activity occurring only between 3:30 a.m. and 4:30 a.m. Reeves and Salman (1993) established a link between access to pasture and the incidence of colic in horses. They reported that there was a significant decrease in the odds of a horse with colic symptoms if the animal had access to pasture. These two studies point to the desire for horses to graze continuously and a decreased likelihood of a colic problem if horses are allowed to graze.
It is the experience of these authors and our field experience that lush, high-moisture spring pasture can also be a colic risk in horses. Colic problems in horses consuming large amounts of high-moisture, low-fibre grass virtually disappeared when horses were offered dry hay while grazing these pastures. Therefore, from a colic management standpoint, it is recommended that horses have access to pasture whenever possible, and be provided with additional dry hay when pastures contain a high-moisture and a low-fibre content (lush spring pasture).
Horses confined to stalls have an increased likelihood of colic (Reeves and Salman, 1993). Many mechanisms could account for this increased incidence of colic. First, stalled horses have the desire to consume forage in a continuous manner; however, they are routinely fed their forage in two distinct meals (morning and evening). Second, stalled horses may not be receiving adequate forage to maintain proper gastrointestinal function. This may be the case with horses being limit-fed restricted amounts of hay and chaff hay to maintain or reduce bodyweight. Lucerne hay typically contains more calories per pound than grass hay or oaten/wheaten chaff. Therefore, horses fed lucerne would be provided fewer kg of hay per day than horses consuming grass hay. Not only are horses fed lucerne receiving fewer kg per day, reducing the amount of time spent eating, but lucerne hay also contains less fermentable fibre than grass hay.
Since horses seem to have an absolute requirement for forage in the diet to prevent colic, it is recommended that a minimum of one kg of dry forage (hay/pasture) per 100 kg of body weight per day is provided. For horses confined to stalls, the selection of lower calorie hays or chaff (grass-type) will provide the horse more kg of hay and mimic the continuous feeding behavior during grazing.
When horses are fed chaff rather than hay there is often a reduction in the quantity of fibre fed, as chaff is very light and fluffy compared to hay. A 20 litre bucket of chaff only weighs a little more than a flake of hay. This means it is common to feed less chaff than you would if you fed hay, and this is especially important in horses that are stabled full time. Another consideration is that chaff is mainly short fibre compared to the long fibre in hay. In cattle there is a requirement for some long stem fibre in the diet and our experience is that there is a higher risk of colic in horses fed all their fibre as short cut chaff.. For that reason do not be concerned if you are feeding rougher cut chaff with has longer fibre length and in fact it is probably a digestive benefit for your horse.
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Quality of Fibre
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The quality of fibre fed can also influence colic potential. Mycotoxins, which are toxic compounds produced by molds, have been linked to colic in horses (Barnett et al., 1995). Do not feed mouldy feeds to horses and store feed to minimise the likelyhood of moulding. Other toxic substances occasionally ingested with forage can also cause colic symptoms.
Another indicator of fibre quality is fibre digestibility. Wheat or oat straw, a highly non-digestible fibre source, has been implicated as causing impaction colic in horses. The high lignin and silica content help the plant hold the grain up and the silica gives it the shiny appearance. Rice straw and rice hulls are even less digestible as they have an even higher lignin and silica content. Impaction may result from a lack of disappearance (fermentation) of material in the hindgut. Horses cannot digest or utilise these poor quality forages as effectively as cattle. Data on the precise amount of poorly digested fibre which can be included in the diets of horses are not available. However, the poor physical appearance and performance of horses fed this type of diet should set practical limitations. Be careful feeding tropical forages as these hays can also be very indigestible.
Enhanced fibre digestibility has been reported with the addition of live yeast culture (Yea-Sacc 1026) to the diet of mature horses. The addition of live yeast culture may provide a mechanism whereby horses can more efficiently utilize forage of marginal quality and we include Yea-sacc in several EQUIVIT supplements and HYGAIN feeds formulated by Kentucky Equine Research. Yea-Sacc can stimulate activity of beneficial microbes in the large intestine, particularly bacteria that digest cellulose. This can lead to an increase in the fermentation of cellulose and other fibre fractions. There are anecdotal reports of a reduction in the incidence of colic when Yea-sacc is added to the diet.
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Grain Feeding
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Since horses are anatomically designed to digest fibre, the addition of grain concentrates to the diet is a potential risk factor for colic. Tinker et al. (1997) reported that daily feeding of grain concentrate from 2.5 to 5 kg/day and above 5 kg/day increased the risk of colic 4.8 and 6.3 times, respectively, compared to horses fed no grain. The exact mechanism for this increased risk for colic was not determined; however, several studies on the site of grain digestibility offer at least a partial explanation.
Normally, grain concentrates contain large amounts of starch that are enzymatically digested with their end products (simple sugars) absorbed in the small intestine. Several factors are known to influence the rate and extent of grain digestion in the small intestine. One factor is the source of starch. Various sources of starch (i.e. oats and corn) differ in the architecture of their starch granule which has a large impact on how well they are digested in the horse's small intestine.
Meyer et al. (1993) reported the prececal (small intestine) digestibility of these two starch sources averaged 84% and 29% for oats and corn, respectively. Starch which is not digested in the small intestine spills into the large intestine where it is fermented by bacteria. Unfortunately, one of the end products of microbial starch fermentation is lactic acid, which irritates the gut lining and decreases intestinal pH. The increase in acidity causes other more prevalent bacteria to die and release potentially fatal endotoxins. All of these situations can potentially cause the horse to colic. Processing the starch in grain (crimping, rolling, grinding etc.) can also influence small intestine digestibility. Grinding corn, for example, increases prececal digestibility from 29% to 45%, while popping corn increased prececal digestibility to 90% (Meyer, 1993).
Finally, the amount of starch fed in a single meal will influence prececal digestibility. Radicke et al. (1991) reported that a coarsely ground corn intake of 3 - 4 g/kg BW resulted in a drop in cecal pH indicating that starch escaped digestion in the small intestine. This level of corn intake would be comparable to feeding a 500 kg horse approximately 2 kg of corn in a single meal.
This knowledge regarding starch digestibility would lend several recommendations to grain feeding in horses to decrease the risk of colic. First, processing of the grain will increase small intestine digestibility and decrease dangerous changes in hindgut acidity. Steam flaking/rolling, pelleting, micronisation and extrusion are efficient methods for processing grains intended for horses. Second, limit the amount of grain provided to no more than 2.5 kg (5 lbs) in a single meal. A number of small meals are preferable to one or two large meals when high intakes of grain are required by the horse.
The use of dietary fat as an energy source is also a valid method to reduce the amount of grain needed in the diet. Don’t forget that forage in the form of hay and chaff can contribute a lot of the energy and protein needed by the horse for the horse that is spelling or in light/intermittent work. Finally, with recent scientific data on the digestion of oat starch , there is new credibility to the long held belief that oats are the best single grain for horses.
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Action if your horse has Colic
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Colic is a veterinary emergency as horses are often in serious pain, early treatment gives better outcomes and the horse can hurt itself when reacting to the pain of the colic. So you need to call your veterinarian, take away feed and water and prevent the horse from hurting itself. Walking a horse with colic may prevent it rolling, but many horses prefer to lie quietly rather than being marched around on the end of a lead rope.
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References
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Barnett, D.T., R.A. Mowrey, W.M. Hagler, Jr., D.G. Bristol and R.A. Mansmann. 1995. The correlation of selected mycotoxins to the incidence of colic in horses. In: Proc. of the 14th Equine Nutrition and Physiology Symposium, pp.242.
Hintz, H. F. 1994. Commonly asked questions about nutrition and colic. Equine Practice, Vol. 16, pp. 10.
Meyer, H., Radicke, S., Kienzle, E., Wilke, S., and Kleffken, D. 1993. Investigation on preileal digestion of oats, corn, and barley starch in relation to grain processing. In: Proc. of the 13th ENPS Gainsville, FL.
Pond, K.R., D.K. Dugan, D.T. Barneet, J.C. Burns and D.S. Fisher. 1993. Grazing behavior of mares and steers on orchardgrass and mares on common bermuda grass. In: Proc. of the 14th Equine Nutrition and Physiology Symposium, pp. 236.
Radicke, S., E. Kienzle and H. Meyer. 1991. Preileal apparent digestibility of oats and corn starch and consequences for cecal metabolism. In: Proc of the 13th Equine Nutrition and Physiology Symposium, pp. 43.
Reeves, M.J. and M. Salman. 1993. Risk Factors for equine colic identified by means of multicentered case-control study. In: Proc. of the 39th Convention of the American Association of Equine Practitioners, pp.93.
Tinker, M.K., N.A. White, P. Lessard, C.D. Thatcher, K.D. Pelzer, B. Davis and D.K. Carmel. 1997. A farm based prospective study for equine colic risk factors. Equine Vet J. 29 :454 -458
Uhlinger, C. 1990. Effects of three anthelmintic schedules on the incidence of colic in horses. Equine Vet. J. 22:251.
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Dr Peter Huntington, Dr Joe Pagan and Dr Stephen Duren
Kentucky Equine Research, Brighton, Vic Australia & Versailles, KY, USA
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