Equine Calorie Consumption: Hay vs Pasture Grazing

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The N.C. Cooperative Extension of Polk County office held a field day last Tuesday, February 23, 2021, which was graciously hosted by two of our Extension Advisory Council members, Terry and Jane Lynch, at their farm near Columbus. In the equine/pasture management session, I discussed how to manage our horses’ calorie consumption as they transition from a mostly hay diet this winter to an abundance of fresh spring pasture. If you enjoy math, here’s an example to follow that shows the big jump in calorie consumption once our horses start grazing more fresh forage:

For this example, I utilized the digestible energy requirement (DE, Mcals) for a horse in light work (1-3 rides per week) listed in the NRC Nutrient Requirements of Horses, which is 20 megacalories (Mcals) per day. If an average-sized horse weighing about 1100 pounds consumed 2% of his bodyweight per day in dry matter of an average quality grass hay (0.91 Mcals/lb. from Equi-Analytical’s online database), he would consume 20.02 Mcals per day, which is enough to meet his entire daily energy requirement. In most all cases, fresh forage from pasture is higher in energy (i.e., calories) than stored hay, but how can we estimate how many calories our horses are consuming while at pasture? If your horses have free access to pasture, they can consume between 2-2.5% of their bodyweight per day. Previously sampled fescue from a North Carolina pasture in April had an energy density of 1.13 Mcal/lb. The same horse in light work grazing about 22 pounds of dry matter from this pasture would consume approximately 25 Mcals per day- 5 extra Mcals than his daily requirement.

Calorie Content of Hay vs Pasture for Horses

For comparison purposes, a growing two-year-old in a training program has a daily requirement of 24.8 Mcals/day. This excess in calorie consumption is enough for this horse to gain a full body condition score in about 2.5 months, and even quicker for a horse that is rarely ridden. Horses that are overweight carry a higher incidence of metabolic diseases such as insulin resistance, laminitis, and cushings, so it’s important to monitor changes in their weight over time. Restricting time at pasture, grazing muzzles, and feeding a lower calorie hay before turnout to prevent gorging are all options to manage our horses’ calorie consumption; however, some horses learn to manipulate whichever system you choose.

Research has demonstrated that some horses learn the turnout routine and speed up their consumption rate while at pasture. Others skillfully master the art of placing the grazing muzzle directly down on top of bunch grasses, such as fescue, to reduce the muzzle’s effect. Try different management techniques to see what works best for you and your horses. If you’re not tired of all the math so far, there’s even a formula developed by researchers at NC State University that we can use to estimate the number of calories your horse consumes based on the number of hours he spends grazing. Feel free to contact me to discuss options specific to your horse and management style.