There has been a considerable debate in the equine community regarding starch and sugar levels in horse feeds. Like fiber and fat, starch and sugars are energy sources that “fuel” your horse. Higher levels of starch and sugars can be indicated for performance or breeding horses, but for some other horses, such levels may not be appropriate. Moreover, various studies have indicated that a high starch & sugar intake has been associated with various disorders in horses such as colic, laminitis, and insulin resistance. The glycemic index is a tool for quantifying the impact of a feed on the glucose response of horses. Cavalor® undertook a study to determine the glycemic index of select Cavalor® feeds and their impact on insulin response.. This study was executed in cooperation with Department of Animal and Food Sciences at the University of Kentucky. This article addresses main results of this study and how this information may help horse owners to select an appropriate feed for their horse.
Feed, blood glucose, glycemic index, and insulin response
Feedstuffs may contain simple sugar and starch. Starch is also digested to simple sugars like glucose. These sugars are usually absorbed in the small intestine. Consequently, the concentration of glucose in the blood will rise after intake of a feed containing starch and sugars.
To what extent the blood glucose will rise depends on many factors. The amount of starch and sugar and the type of starch in the feed are important factors for the amount of glucose produced. In the last decade, the glycemic index (GI) has been applied in horse nutrition to rank the blood glucose response between feedstuffs after intake. Oats are used as reference feed with the glycemic index of oats is set at 100. A feed ranked over 100 will induce more blood glucose in a given amount of time than oats.
A horse feed with a low GI can be classified as a feed that contains low amounts of sugar and starch. Thus, such feed will have a low glycemic response. Hay has for example a very low GI. A high-GI feed will contain starches and sugars that are digested and absorbed rapidly in the small intestine. Therefore, such a feed will have a high glycemic response.
Insulin is a hormone involved in regulating carbohydrate and fat metabolism in the body. The blood insulin concentration is often measured when the GI is determined. Insulin is a hormone that causes cells in the skeletal muscles and fat tissue to absorb glucose from the blood. However, there are various disease conditions where the response of insulin towards glucose levels in the blood may be compromised, e.g. if your horse is insulin resistant (IR). Horses and ponies that are IR or suffer from a disorder that involves IR may benefit from a low-glycemic diet.
Study: The GI index and insulin responses of selected Cavalor® feeds
Cavalor® Strucomix Original and, more recently, Cavalor® FiberForce were developed to provide a dietary solution for horses in need of a moderate or low GI feed respectively. Cavalor® FiberForce has been especially designed for horses in need of a low GI feed. In addition, this feed could also be used for horses suffering from complex problems such as a combination of IR and a compromised forage intake, motility problems, or laminitis. However, horses with a compromised forage intake still need to take in sufficient fiber. Cavalor® FiberForce contains not only a low sugar & starch content, but also a fiber level comparable to hay. Therefore, the GI and insulin response of Cavalor®’s moderate to low GI feeds were also compared with hay in this study. Both hay and oats were included as reference feeds in this study.
Feeds like Cavalor® Perfomix and Cavalor® Superforce have been designed to provide energy for types of exercise in which “carbohydrate sources” supply a large percentage of the energy required to the horse. These high-GI feeds were selected for this study as they differ in composition. In practice, these feeds are typically used for performance horses. In table 1, the non-structural carbohydrate content (NSC) of the select Cavalor® feeds used in this study are presented.
Feeds designed for leisure horses and easy keepers or feeds marketed as low starch or low in NSC should have a lower GI index. Consequently, these feeds should induce a lower insulin response than oats. Cavalor® Strucomix Original can be categorized as a feed with a GI and insulin response higher than hay and Cavalor® FiberForce, but lower than oats as shown in Fig. 1. This figure also shows that Cavalor® FiberForce can be classified as a very low GI feed. Feeding Cavalor® FiberForce also resulted in very low insulin response (Fig. 2 and 3).
Cavalor® Perfomix and Cavalor® Superforce are especially designed for performance horses. The results of this study show that Cavalor® Perfomix is a high glycemic feed and that Cavalor® Superforce produces a similar amount glycemic response as oats despite having the highest starch level (Fig. 1). Interestingly, Cavalor® Superforce showed a somewhat lower and more or less steady glucose and insulin response between 1 to 4 hours after intake. Feeding Cavalor® Superforce resulted in lower blood glucose (data not shown) and insulin (Fig. 2) levels between 4 and 6 hours after feeding when compared with Oats and Cavalor® Perfomix. It is likely that the higher inclusion of puffed cereals in Cavalor® Superforce may explain this phenomenon. As has been shown in other species, “puffed grains” may result in a slower release of starch into the small intestine than conventionally processed grains. The slower release of starch may explain the lower glucose and insulin levels observed from this feed.
How do these results help you to better feed your horse?
A low or high-GI feed cannot be simply classified as “good” or “bad” for your horse. If your horse is kept individually, it is preferable to select the feed that best matches your horse’s needs. The type, level and the amount of work, along with the character, breed, condition, and health status of your horse determines what ration and Cavalor® feed would be best to meet your horse’s needs. This is particularly true regarding the amount and type of energy source you have to feed your horse. The Cavalor® team has various experts who can further help you selecting the right feed for your horse.
Horses performing in equestrian disciplines involving significant amounts of short-term, high-intensity exercise (racing, jumping, barrel racing and cutting) may benefit from feeds that provide highly digestible carbohydrates to help “fuel” their muscles. The GI and insulin response of a feed may be important for trainers or riders to determine the best feeding time for their horses before or after a race and/or competition. Cavalor® Perfomix can be fed when a feed with a stronger insulin peak is desired. Cavalor® Superforce can be used for performance horses that need a high energy feed with a less pronounced glucose and insulin peak.
High glycemic feeds like Cavalor® Perfomix and Cavalor® Superforce are not indicated for insulin resistant horses or “easy keepers.” Dietary strategies that include a moderate (Cavalor® Strucomix Original) or low GI feed (Cavalor® FiberForce) will be more appropriate. This study clearly showed that Cavalor® FiberForce has the lowest GI and insulin response. Therefore, Cavalor® FiberForce is a very appropriate supplementary feed for IR horses or horses prone to laminitis which both require a low GI feed.
Fig. 1: Glycemic Index (blood glucose response relative to oats).The total amount of blood glucose increase when feeding 1 kg DM of test feed / 500 kg horse. Bars with values greater than 100 indicate that a higher blood glucose level than that produced when feeding a comparable amount of oats, which is set at 100. Cavalor® FiberForce showed the lowest GI and while Cavalor® Perfomix had the highest.
Fig. 2: Plasma insulin responses during time of selected Cavalor® feeds. This graph clearly shows that the ranking order of Cavalor® feeds from least plasma insulin reponse to greatest: FiberForce, Strucomix Original, Superforce, and Perfomix.
Fig 3a: Plasma glucose concentrations over time of hay, oats, and Cavalor® FiberForce. Cavalor® FiberForce has a similar glucose response as hay and a very low GI.
Fig 3b: Plasma insulin concentrations over time of hay, oats, and Cavalor® FiberForce. The graph shows that Cavalor®FiberForce has a similar insulin response as hay and is a safe supplementary feed for IR horses.
Table 1: Non-structural carbohydrates (NSC) of selected Cavalor® feeds (%)
|Cavalor® Strucomix Original||15|
* NSC value of the hay that was used in this study and not reflective of the NSCs of all hays. In practice the NSC levels may vary considerably between different hay types and cuts. Horse owners should analyze their hay if their horse is sensitive to a high NSC content.
Q & A
Q: Is the GI simply a reflection of the amount of starch and sugars in the diet?
A: The level of starch and sugar intake is one of the most important determinants for the GI of a feed. However, the blood glucose and insulin response to a feed is dependent on the rate of digestion and absorption of that feed. The rate of digestion can be influenced by several factors, such as the type of starch, processing technique, and interactions with other nutrients in the diet. Variations within a processing technique, such as the flake thickness of flaked cereals, may also result in different glucose and insulin responses.
Q: What Are Puffed Grains?
A: Cavalor® uses puffed grains in various feeds for performance horses. The horse is able to digest this type of starch very well. If you provide energy in the form of starch to performance horses, high digestibility is preferred to prevent gastrointestinal problems.