One of many riders’ worst fears is arriving at the paddock to find their horse showing signs of extreme soreness in the front feet. After a callout from the vet, it’s determined the horse has a mild case of laminitis. How could this happen? The horse’s diet hasn’t changed, it’s not excessively overweight nor has its training regime changed.
Unfortunately, laminitis can occur for many different reasons, with one potential cause being sensitivity to sugar and starch in the diet, resulting in insulin resistance. If the horse is in competition, it raises the question of how it can be fed for performance and to prevent the recurrence of the disease. To understand what to do nutritionally, it is important to start at the beginning.
Horses are well-suited to a high-carbohydrate diet consisting predominantly of plant forages, which can be divided into structural carbohydrates (SC), which make up the fibrous portion of the diet and originate from the plant cell wall, and the non-structural carbohydrates (NSC) – sugar and starch, which originate from inside the plant cells.
Horses in work require more energy than spelling horses, which is why they are often fed higher carbohydrate feeds. Specifically, performance horses are often fed cereal grains with high NSC content.
Sugar and starch (such as from oats, corn and barley) provide fuel for performance that is quicker to metabolise than structural carbohydrates, as they are rapidly broken down in the small intestine, while structural carbohydrates must be fermented by bacteria in the large intestine. But unfortunately, sugar- and starch-rich meals may increase equine digestive and metabolic disorders, and may promote insulin resistance and lead to laminitis.
Insulin resistance (IR) is becoming more common. It’s a disease in which tissues (muscle and liver) have become resistant to the effect of insulin, the hormone that facilitates the uptake of glucose from the blood into the tissues of the body. When a horse becomes resistant to insulin, they must produce more insulin to clear the blood of glucose. Horses with IR have chronically high levels of insulin and often have high levels of blood glucose, which can have damaging consequences for circulation and is thought to potentially facilitate laminitis.
While low carbohydrate feeds (low GI), such as vegetable oils, beet pulp and lucerne chaff, provide an alternative energy source for horses sensitive to starch and with a history of digestive and metabolic disorders, some commercial feeds may not suit performance horses. Horses in work need some dietary sugar and starch in order to provide enough energy to fuel performance. Any speed work or jumping effort that requires explosive muscle contraction will benefit from sugar and starch in the diet.
There is a lack of information available for nutrition and management strategies for horses who have recovered from laminitis, or have a sensitivity to sugars and starches and are now returning to competition. These horses are difficult to manage because calories must be provided for weight maintenance or gain, without causing a relapse. This becomes even more important when horses are exercising and using more calories. Feeding recommendations should therefore be tailored to the individual. The following guidelines should serve as a starting point:
Ideally, feeding strategies for horses kept under intensive conditions would mimic the pattern of a grazing animal. For stabled horses, increase the availability of hay (or a variety of different forages) and pasture. Provision of more frequent and smaller concentrate meals throughout the day is also recommended. Extending eating time by diluting the energy density of the meal (eg. chaff mixed with concentrates) or feeding forage such as hay before concentrate may be helpful.
For hard-working horses, the provision of roughage is often restricted in favour of grain concentrates to ensure adequate energy. However, there is considerable evidence associating low roughage diets with digestive disturbances and behavioural problems. A minimum amount of roughage ranging from 1 to 1.5% of body weight has been recommended.
It would be prudent to have hay analysed to determine actual sugar content, and fibre intake can be increased by feeding other sources of roughage such as sugar beet pulp or soya hulls, all of which are highly digestible fibre sources. This approach also helps to decrease the reliance on grain for energy, thereby decreasing risk of digestive disturbances.
These so-called “superfibres” contain digestible energy equivalent to oats, while not producing any symptoms of grain overload.
The feeding of large meals rich in starch and sugar can overwhelm the digestive capacity of the small intestine and upset the microbial population of the hindgut. No more than 2kg of grain or sweet feed mix should be fed in a single meal (for a 500kg horse).
Starch digestibility varies with the type of grain and the nature of any mechanical or thermal processing. Milling, grinding, and heat treatments (eg. steam flaking, micronisation, extrusion) improve the starch digestibility of oats, barley and corn. Overall, oats appear to be the safest source of starch for horses.
Alternatively, the energy demands of performance can be readily met by provision of other sources such as rice bran oil (fat) and non-starch carbohydrates (eg. sugar beet pulp, soya hulls). Commercial concentrates made with these ingredients contain varying amounts of starch and sugar, but will be substantially lower when compared to straight cereals or sweet feed mixes. HYGAIN ZERO® is a unique Low Carb-Low GI feed for all horses, with less than 1.5% starch, less than 5.5% NSC and no grain or grain by-products.
When compared to hay and chaff, superfibres such as soy hulls and beet pulp contain lower indigestible material (eg. lignin) and higher amounts of digestible fibres which translates to a higher energy yield. HYGAIN® offers a well-fermentable fibre source called HYGAIN® MICRBEET® unmolassed micronized sugar beet flakes suitable for all equines.
Adding stabilized rice bran oil, such as HYGAIN® RBO® Equine Performance Oil® or HYGAIN TRU GAIN® to a horse’s diet will increase the calorie content (250ml of oil provides 9.74 Mj of digestible energy). It is recommended to feed up to 75-100g oil per 100kg bodyweight/day. This daily amount should be divided into 2-3 meals and introduced gradually (eg. starting at 50 ml/day).
Supplements & exercise
There is considerable interest in the use of feed additives, such as live yeast culture and bacterial species, as a strategy to minimise the negative effects of cereal-based diets. Yeast cultures might be beneficial for stabilisation of the hindgut environment when high cereal diets are fed.
But dietary therapy alone may not be sufficient to reverse insulin resistance. Research has shown that both obese and lean horses had improved insulin sensitivity after seven days of moderate exercise training.
If careful management and nutritional guidelines are followed, the performance horse can usually return to competitive condition after a mild laminitic episode. Veterinarian recommendations should be taken into account and the rider needs to recognise that management of the condition will be ongoing. ■