Over time, horse feeds manufactured to meet equine energy and nutrient needs have evolved from mixes of whole grains to textured, pelleted, and extruded types. The extrusion process is designed to improve digestibility; however, research into whether it does has mainly been conducted in other species.
So Kristine Ely, a graduate student at the Virginia Tech Middleburg Agricultural Research and Extension Center, in Middleburg, Virginia, looked at feed processing method’s effect on digestibility and metabolic response in horses. She presented her findings at the 2019 Equine Science Society symposium, held June 3-6 in Asheville, North Carolina.
In her study, Ely measured the body weight, feed intake, and metabolic responses of four Thoroughbred geldings consuming three diets:
- Hay only;
- 0.75% body weight (BW) pelleted feed and 1.75% BW hay, split between two meals daily; or
- 0.75% BW extruded feed (made of the same ingredients as the pelleted feed) and 1.75% BW hay, split between two meals daily.
She fed the horses one of the diets for 25 days, took blood and fecal samples at the end of that period, then moved on to the next diet and repeated the study. Ely found that:
- Horses consumed all feed readily;
- Dry matter intake and digestibility did not differ between feeds;
- Digestible energy (the calories available to the horse after digestion) tended to be higher for the extruded feed than the pelleted;
- Glucose and insulin responses after morning meals didn’t differ between feeds;
- Glucose and insulin responses after evening meals were higher with the extruded feed than the pelleted. This is important to know, she said, because “easy-keeper-type horses would do better with a smaller response. However, horses with higher energy needs might find an increase beneficial.”
While identical feeds processed using extrusion or pelleting had no differences in digestibility, a “better understanding of how horses respond metabolically to meal feeding can help us design diets for horses with special dietary needs,” Ely concluded.
She acknowledged that larger study sizes are needed to further explore feed processing methods.