Energy Needs

Numerous factors can influence the energy requirements of the horse. These include environmental conditions, the horse’s functions and activity (including intensity and duration of work, weight and ability of the rider, and conditions of the traveling surface), and its physical condition and degree of fatigue. Even when all of these factors are identical, individual horses vary in their energy needs. The average amount of energy needed should therefore be considered only a general guideline—an amount that will be relatively close for a group of horses but either inadequate or excessive for some individuals. The amount of digestible energy (DE) needed for maintenance (i.e., for no weight change by the mature, idle nonreproducing horse at moderate environmental conditions) by the average horse weighing 1320 lbs (600 kg) or less can be calculated from the following equation.

Mcal DE/day = 1.4 0.03 (kg body wt or lbs 2.2)

However, energy needs are lower per unit of body size in horses weighing over 1320 lbs (600 kg) and can be calculated from the following equation.

Mcal DE/day=1.82(0.0383kg body wt or lbs2.2)-[0.000015(kg body wt or lbs2.2)2]

Estimates of energy requirements for physical activity or work depend primarily on the total weight carried (horse, intestinal fill, rider, and tack) times the distance moved, but increase with decreasing ability of the rider and physical condition of the horse, difficulty of the terrain and surface covered, and other factors. For ponies and light horses, the Mcal DE/day for light, medium, and intense work has been estimated to be respectively 1.25, 1.50, and 2.0 times that needed for maintenance; with light work being activities such as Western and English pleasure, bridle path, hack, and equitation; medium work being ranch work, roping, cutting, barrel racing, and jumping; and intense work being race training, endurance racing, and polo. Digestible energy needs greater than those required at rest have also been estimated in Mcal/hr/100 kg (220 lbs) total weight carried to be 0.17 for a slow walk; 0.25 for a fast walk; 0.6 for a slow trot; 1.0 for a medium trot or slow lope; 1.3 for a fast trot; 2.0 for cantering, galloping or jumping; and 3.9 for a fast gallop.

For draft horses, energy needs depend on factors such as the size of the load pulled and the type of work. Increasing maintenance energy needs by 10%/hr of field work is a reasonable estimate.

For pregnant mares, energy needs do not increase greatly until the last 3 months of gestation, which is when the greatest development of the fetus occurs. Energy requirements for the ninth, tenth, and eleventh months of pregnancy average, respectively, 1.11, 1.13, and 1.20 times that needed for maintenance. During the first 3 months of lactation, energy needs average 1.8 times, and from 3 months until weaning, averages 1.5 times that needed for maintenance. For young horses, energy needs increase with increasing growth rate and size, but per unit of body weight decreases as the horse gets older and bigger, and growth rate slows.

This article is from "Feeding and Care of the Horse", second edition, by Lon D. Lewis, Lippincott Williams & Wilkins, 1995. Reprinted with permission from the publisher.