Many a horse or pony owner has restricted their overweight equid’s turnout time in an effort to help him shed pounds. And while researchers know weight loss helps improve horses’ overall health, until now they haven’t known exactly what impact restricted grazing has on the equine gastrointestinal health or calorie intake. A group of North Carolina State University (NCSU) researchers recently set out to determine if restricted pasture access affected horses’ intake rate, energy intake, and hindgut fermentation.

The research team, led by Paul D. Siciliano, PhD, associate professor in the NCSU Department of Animal Science, separated eight mature idle geldings into four groups and allowed each group pasture access for either 3, 6, 9, or 24 hours for seven days. After seven days, the team reassigned the groups to a different turnout treatment on an ungrazed pasture. By the end of the four-period study, each horse had been subjected to each pasture treatment. When not on pasture, the horses stayed in drylot pens with access to water and salt; horses in the three- and six-hour treatment groups had free-choice access to a low-quality grass hay. Throughout the study, the team recorded the amount of hay consumed and collected fecal samples from each horse on each Day 7.

The team also measured or estimated pasture plant composition, herbage mass (used to quantify pasture available to an animal), grazing height, and forage preference for each period. Pasture composition consisted of 54.7% crabgrass, 28.3% tall fescue, 8.2% fox tail, 1.14% dallisgrass, 0.86% weeds, and 6.6% bare ground. They noted no difference in digestible energy concentrations (DE) or initial herbage mass for each pasture. However, less pasture was available during periods 2 and 3 compared to 1 and 4