It’s no secret that a restricted diet could help your horse lose weight, but there can be consequences when horses eat more like humans, with only two or three meals per day, than how they were designed to—grazing small amounts of forage almost all day long. However, with the advent of slow feeders, horse owners and managers can extend foraging time while still limiting the amount of hay that’s fed. And recent study results suggest this might be the answer to keeping your horse healthy while he sheds weight.

In a four-week study, researchers from the University of Minnesota employed eight overweight adult Quarter Horses with an average body weight of 563 kilograms (just over 1,240 pounds) and a body condition score (BCS) of just over 7 out of 9. After an acclimation period, the team separated the horses into two groups of four and fed them a diet consisting of a ration balancer and cool season grass hay fed at approximately 60% of their maintenance digestible energy requirement, twice daily. Horses consumed hay either from a slow-feed haynet or from the floor of their stall.

To evaluate the effects of feeding treatment on horses’ glucose, insulin, cortisol, and leptin levels, the researchers collected blood samples on Days 0, 14, and 28 at several time points (one hour before feeding, one hour after the morning meal, every 30 minutes for the following three hours, and then hourly until the evening meal). They team repeated this schedule for the evening meal.

On those same days, they assessed horses’ BCS, took body measurements, and measured rump fat and longissimus dorsi (back muscle) muscle depth and thickness via ultrasound. They also measured the horses’ body weight using a livestock scale.

Ultimately, the team confirmed that horses in the floor-fed group consumed hay at nearly twice the rate as those in the net-fed group throughout the course of the study. Other findings included:

  • Dry matter intake did not vary by treatment;
  • All horses lost weight throughout the course of the study;
  • A slight reduction in longissimus dorsi thickness was noted for horses fed from the haynet, but not the floor; and
  • Glucose and insulin values increased, whereas cortisol and leptin levels decreased throughout the study.

“A possible explanation for the increased glucose level is an increase in cytokines (proteins important in cell immune response) over time,” noted researcher Krishona Martinson, PhD, associate professor and equine Extension specialist in the department of animal science.

The researchers confirmed that owners can use slow-feed haynets in conjunction with reduced feeding rates to safely and effectively decrease body weight in horses. However, “before starting a restricted diet, horse owners should first talk to an equine nutritionist (to ensure the ration is balanced) and their veterinarian (to ensure a healthy weight loss will be achieved),” Martinson advised.

The study, “The Effect of a limit-fed diet and slow-feed hay nets on morphometric measurements and postprandial metabolite and hormone patterns in adult horses,” was published in Journal of Animal Science