It can be challenging for veterinarians and owners to manage obese horses’ weight. Client compliance is often poor when veterinarians recommend weighing hay and curtailing the horse’s daily intake. Plus, there are concerns about horses having fewer opportunities to chew and developing gastric ulcers from fasting and stress. So, researchers in Britain examined oat straw as a lower-calorie fiber alternative to high-quality grass hay.
Feeding Straw to Horses
Protocols to curtail a horse’s feed intake include slow feeders and/or grazing muzzles. Yet, these strategies often don’t provide horses with sufficient chewing opportunities. The researchers considered offering straw to partially replace better-quality, higher-calorie forage. Straw is high in fiber and relatively low in calories compared to high-quality hay. One potential benefit of including straw in the diet, besides helping with satiety, is that the more a horse chews, the more saliva they secrete to buffer stomach acid. In a previous study, horses consumed 50% straw and 50% haylage and showed reduced insulinemic responses. This combination also promoted weight loss and chewing opportunities. There have been concerns that a straw diet might increase the risk of impaction colic, especially in horses with poor dentition. The authors noted this risk is minimal as long as straw comprises no more than 50% of the forage diet and is introduced slowly. However, they point out that horses with dentition issues should not eat straw.
Study Population
This study included eight horses aged 8-20 years and examined how feeding 50% of horses’ forage ration as oat straw affects chewing rates and consumption. The horses did not have gastric ulcers, dental problems, colic, or other gastrointestinal disease in the 12 months prior to the study. All had been fed haylage during that year and had not been fed or bedded on straw. They received no additional forage or supplement during turnout. Horses were offered their food in hay nets at 8:30 a.m. and 4:30 p.m.
The researchers started by feeding 75% haylage and 25% oat straw to two groups of four horses. They measured body weight, chewing, and consumption rates on Days 1 and 7. Chewing rate was counted at 1- to 10-minute intervals, captured on video for five minutes in the morning. They measured consumption rate by weighing the forage consumed in one hour and again an hour later.
Study Results
The chewing rate of a straw-inclusion diet was less than the control (haylage only) diet. Because straw was a novel feed, the horses spent considerable time exploring the forage and moving the hay net around to access more palatable haylage; this resulted in less time chewing. Despite this seeking behavior, the horses did not display signs of frustration, such as muscle tension, aggression, displacement, or stereotypies. These results indicate that adding straw slows chewing rate and intake yet provides some degree of mental stimulation comparable to a horse foraging in pasture. By Day 7, chewing rates increased, likely due to an adjustment to the modified diet and because the horses might have become hungrier by then.
Consumption rates of oat straw were less than for hay only. The authors said lower straw consumption rates might be due to “lower palatability and digestibility of oat straw, increased gut fill, and more demanding mastication.” The search behavior and forage sorting further slowed consumption in the initial days. The authors suggested that longer retention of straw in the gastrointestinal tract might decrease ghrelin secretion to improve satiety.
A 50% straw diet mixed with hay resulted in an 80% increase in feeding time, in part because the hay nets in this study had 1.7-inch (4.5 cm) openings. The authors recommended repeating the study by feeding on the floor.
Final Thoughts
In summary, the use of no more than 50% oat straw in a horse’s diet to provide lower energy might be effective for weight control in obese horses with good dentition. It might benefit horses both psychologically and physiologically to limit length of fasting periods while providing horses with chewing opportunities.
Reference
Mostert NL, Williams K, Witherow BA. A Preliminary Study on Feeding Straw to Horses and Its Effects on Equine Chewing and Consumption Rates. International Journal of Equine Science. Oct 2024, vol. 3 (2), pp. 115-122
Related Reading
- How to Feed Horses Prone to Endocrinopathic Laminitis
- Disease Du Jour: EMS and ID
- Managing EMS and ID Horses
Stay in the know! Sign up for EquiManagement’s FREE weekly newsletters to get the latest equine research, disease alerts, and vet practice updates delivered straight to your inbox.
