With countless types of grains and concentrated feed available for performance horses, some horse owners might wish for a simpler approach to feeding their equine athlete. Well here’s some good news for these owners: According to recent study results, a diet devoid of concentrates and entirely based on forage could be suitable for some high-performance equine athletes.

"There is an urgent need for diets that support the natural digestive function and behavior of horses," said Anna Jansson, professor at both the Swedish University of Agricultural and Sciences and Holar University College on Iceland.

"We thought that a high-fiber diet (forage-only) would improve the aerobic energy metabolism and thereby improve VLa4 (velocity when plasma lactate concentration is 4 mmol/l)," reported Jansson.

To test their hypothesis the researchers compared how a high-energy, forage-only diet (F) and a forage-concentrate diet (FC) affected the exercise performance of six Standardbred geldings in race training. The F diet consisted of high-energy haylage fed at 2.2% of horse’s body weight (BW). The FC diet was 50% concentrate (soybean meal, wheat bran, and oats) and 50% haylage. Both diets, estimated to be equivalent in caloric and protein content, also included a mineral/ vitamin supplement to meet the National Research Council’s nutrient requirements.

The horses acted as their own controls, consuming both the F and FC diets during two 29-day study periods.

During each study period, horses underwent interval training (four intervals of 600 meters) on nine different days, with at least one day of rest in between. On day 25 of each period, horses were given an incremental exercise test on a treadmill. Body weight and condition were recorded and muscle biopsies and blood samples were collected before, during, and after the exercise test.

Researchers noted several differences between the two diets, including:

  • VLa4 tended to increase for horses while on F diet (indicative of better performance);
  • Blood pH was higher during exercise on diet F, indicating that this diet could counteract parts of the acidotic effect of intensive exercise; and
  • Muscle glycogen (important fuel for strenuous exercise) content was higher in horses on diet FC.

"Further studies are needed to determine whether total muscle glycogen storage capacity is reduced on a forage-only diet or whether it is only the rate of synthesis that is reduced," Jansson noted, adding that "high-energy, forage-only diets are an interesting alternative to conventional diets."

The study, "A forage-only diet alters the metabolic response of horses in training" was published in Animal in May 2012. It can be viewed online.