Tips for Weight Loss in Horses
Methods of weight loss are of interest for a large portion of the equine population, particularly as knowledge and awareness of the association of excess weight and health risks is more widespread. Excess body weight in horses and excess adipose in key areas of the body (neck, shoulder, and tail head) is associated with development of insulin resistance, metabolic syndrome, laminitis, Cushing’s disease, body temperature dysregulation, joint disease, respiratory dysfunction, and others (American Association of Equine Practitioners, 2005; Goer, 2008). Because of these risks, all horse owners should be mindful of their horses body weight and body condition score and be prepared to make adjustments in feed and exercise to help manage weight.
In adjusting diets for weight loss, keep in mind all feed changes should be made over weeks and that weight changes – even in the right direction – should ideally be gradual and steady. Approximately 1% of body weight loss per week is a reasonable goal (Goer, 2010). Before making changes, take time to assess your horse’s current diet, which will include weighing all feeds and considering their calorie content, reviewing your horse’s turn-out time and access to forages, and determining if anything else is a contributing factor, such as treats, supplements providing calories, or medications that affect weight loss/gain. From here, we should assess how many calories your horse needs for maintenance and its level of work and compare this to calories being consumed, which your Science Supplements nutritionist would be happy to help with.
After these calculations are complete, we can begin to assess what diet changes may be needed. Simply a reduction in feed intake of 10-20% may be effective to induce weight loss (Gill et al., 2016), but switching feeds may also be appropriate and beneficial for both weight loss and metabolic risks. These changes will be unique to your horse and its diet, but some common steps are replacing high “nutrition” grass and hay, as immature, soft bladed forages have higher calorie and lower fiber content with – frankly – lower quality forages, since mature, more stemmy, forages with seedheads present have lower calorie and higher fiber content (National Research Council, 2007). Horses on alfalfa hay can be switched to grass hays, as they are lower in calorie content and higher in fiber (National Research Council, 2007). Higher starch/sugar/calorie concentrates can be reduced or replaced with higher fiber/lower calorie feeds such as senior or complete feeds, or specifically lower calorie content feeds are commercially available. Supplemental fat intake should be limited, although replacing high starch/sugar feeds with high fiber/fat feeds may be appropriate in some instances, as long as calorie content is still considered carefully. Further, after a diet assessment, we may find that your horse doesn’t need concentrate feeds at all because there are plenty of calories given from forages, so in this case a vitamin/mineral balancer and possible protein supplement can be given to ensure basic needs are met with minimal added calories. Treats can be minimized and/or replaced with low calorie options – such as baby carrots, cucumber, celery, or low sugar cereals like Cheerios and plain granola.
Changes in turn-out schedules should be considered with a critical mind, as reducing turn-out time to reduce calorie intake is not always as effective as it seems at first. Horses have been shown to be able to consume more grass per hour when given less time at turn-out, meaning they eat faster and bring in more calories in less time when turn-out is restricted (Glunk et al., 2013). Instead, switching to more mature pastures if possible or the use of a grazing muzzle may be better options (Glunk et al., 2014), and this still allow horses to move freely and get the exercise associated with pasture turn-out. For horses in even greater weight loss need or for whom starch/sugar access should be limited due to metabolic concerns, turn-out to a dry lot may be more appropriate and hay can be provided in a controlled way – such as using slow feeders or hay nets.
The other aspect of weight loss should include increased activity level by developing a regular exercise schedule – ideally at least 3 times a week, at 20-30 min per session (Goer, 2010). An exercise and conditioning program should be designed with your horse’s needs and capabilities in mind to prevent any injuries that would halt the exercise program and potentially lead to additional weight and health concerns. In general, exercise should be geared towards loss of adipose tissue, which entails aerobic exercise – traditionally lower intensity for longer duration – for example 20 min of moderate energy trotting. Faster or sprint style work is more specifically anaerobic work, which uses carbohydrates for fuel and is less helpful in addressing excess adipose. While combinations of aerobic and anaerobic training is typically required for most equine disciplines, aerobic exercise is required for weight loss.
However, once a horse is fit enough for more demanding exercise, the use of interval training can be an effective conditioning program for weight loss due to its demands on both carbohydrates and adipose and is actually even more effective for weight loss than only aerobic training when employed correctly. An example of an interval training session would begin with a warm up at the walk and trot but then involve short duration, energetic cantering for approximately 1 min, followed by moderate energy trotting for 2-3 min, then return to 1 min cantering followed by 2-3 min trotting, and so forth. The reason this back-and-forth is effective is because during the anaerobic canter sessions, muscle tissues use the readily available carbohydrate energy sources stored in muscles so that when the horse returns to trotting, the muscles are more apt to rely on adipose for energy during the trot sessions. Simultaneously, while trotting, the muscle metabolism rebuilds the readily available carbohydrate source back up. But around the same time carbohydrates stores are rebuilt, it’s time for another canter session that depletes these stores again. Essentially, with well employed interval training, trot sessions are using adipose for energy almost exclusively. This is counter to an all-trot training session where it would take more time for just trotting to use up the available carbohydrates until the muscles switched over to using the adipose for energy, and thus the net result is more adipose is consumed in 20 min of interval training that what is consumed in 20 min of only trotting.
Overall, weight loss for equines is a multi-dimensional process that often requires a variety of management and dietary changes. Even with alterations in place, weight loss will likely be a gradual process over many months to achieve significant weight changes. When considering substantial changes in diet and exercise, consult with your veterinarian and nutritionist to ensure your horse’s health needs are covered.
American Association of Equine Practitioners. Overweight Horse: a Bayer Healthcare Animal Health Brochure. 2005.
Geor RJ, Metabolic Predispositions to Laminitis in Horses and Ponies: Obesity, Insulin Resistance and Metabolic Syndromes. Journal of Equine Veterinary Science. 2008;28(12):753-759
Geor RJ. Nutrition and Exercise in the Management of Horses and Ponies at High Risk for Laminitis. Journal of Equine Veterinary Science. 2010;30(9):463-470
Gill JC, Pratt-Phillips SE, Mansmann R, Siciliano PD. Weight Loss Management in Client-Owned Horses. Journal of Equine Veterinary Science. 2016;39:80-89
Glunk EC, Pratt-Phillips SE, Siciliano PD. Effect of Restricted Pasture Access on Pasture Dry Matter Intake Rate, Dietary Energy Intake, and Fecal pH in Horses. Journal of Equine Veterinary Sciences. 2013;33:421-426
Glunk EC, Sheaffer CC, Hathaway MR, Martinson KL. Interaction of Grazing Muzzle Use and Grass Species on Forage Intake of Horses. Journal of Equine Veterinary Science. 2014;34(7):930-933
National Research Council. Nutrient Requirements of Horses: Sixth Revised Edition. 2007. Washington, DC: The National Academies Press