The Horse

FEB 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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NUTRITION SARAH EVERS CONRAD | The Horse February 2019 39 S ome of the biggest indicators of a horse's health are his body condition, weight, and muscle development. So if you're starting to see your horse's ribs, or if he has a less-than- desirable topline— the muscles that support the spine, neck, and hindquarters—then he might need to build weight or muscle. But what is the difference between adding weight and muscle? How do you know which your horse needs, or is he deficient in both? And, then, how can dietary changes help your horse bulk up? Dietary Energy 101 It's important to understand dietary energy and how it relates to a horse's food sources. Basically, energy equals calories, which are measured in kilocalories. In horses, which need thousands of kilo- calories per day, energy requirements are expressed as megacalories (Mcal). There are various types of energy— gross energy (GE), digestible energy (DE), metabolizable energy (ME), and net energy (NE)—but, for the purposes of this article, we'll focus on DE. This is the energy listed on feed labels and that nutritionists reference most. It's the energy that can be digested from a feed after adjusting for the energy lost in fecal output. Because calculations within the equine nutrition industry vary, DE values of feedstuffs are considered estimates. For energy, horses consume fat, carbo- hydrates, and protein. Fats are the most calorically dense feed, at 9.4 kcal/gram of GE (the heat produced when a feed is completely oxidized, or burned). Carbs offer 4.15 kcal/gram, and proteins 5.65 kcals/gram. Carbohydrates (fiber, starches, and sugars) are the main components of for- ages. Horses require them for digestive health, to help buffer stomach acid, and as a good energy source. Protein is the least-efficient energy source, says Russell Mueller, MS, PAS, a member of the Equine Research and Innovation Team at Cargill Animal Nutri- tion, in Minneapolis, Minnesota. Horses can expend more energy digesting protein than they gain from it, he says. Now let's think about how a veterinar- ian or nutritionist might recommend you add weight, muscle, or both to a horse. Note that if a horse is calorie-deficient, he will also be muscle-depleted. You cannot build muscle without adequate calories, says Clair Thunes, PhD, an independent equine nutritionist and owner of Summit Equine Nutrition, in Gilbert, Arizona. Evaluating the Horse The first thing to do is evaluate the horse to see where he falls on the Hen- neke body condition score (BCS) chart (, says Mueller. Ideally, the horse should score between a 4 and 6, meaning you can feel but not see his ribs. His withers, neck, and shoul- ders should be rounded, and the withers should have a layer of fat over them. The horse has a crease down the back, but it is not pronounced. The backbone, tailhead, and hip bones also have some fat cover. If your horse is ribby (and a veterinar- ian has ruled out underlying health issues causing weight loss), he needs more calo- ries in his diet, says Mueller. If the horse is angular over his topline (withers, back, loin, top of the hip, and croup region) and/ or is sunken in around the neck, he needs to build muscle. Developing the topline is important because it plays a vital role in how a horse performs and handles when ridden. Adjusting the protein and amino acids in the diet can help. Adding Calories for More Fat Cover Each horse requires a minimum DE per day for maintenance (to stay the same weight). Different activity levels increase daily DE requirements. You can find these values in the National Research Council's (NRC) 2007 Nutrient Require- ments of Horses, although many horse owners simply consult their veterinarians or nutritionists about their horses' nutri- tional needs. These experts can evaluate what nutrients each horse is taking in with his base diet to see if that diet is ISTOCK.COM Bulking Up Does your horse need to gain weight, muscle, or both? You can't put weight or muscle on your horse with- out adequate calories.

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