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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40 February 2019 The Horse | TheHorse.com appropriate or needs to be changed. For a horse to gain weight, it takes an increase of about 20 Mcals of DE above maintenance to gain 1 kilogram (2.2 pounds). However, this varies depending on grain composition and energy sources. To move up one score on the Henneke scale, says Thunes, a horse needs to gain 16-20 kilograms (35-44 pounds), but this varies depending on the horse's weight. Assuming your horse needs 20 kilograms to move up the scale, he must consume a total of approximately 400 Mcals above maintenance needs. Thunes presents two possible scenarios for adding more calories: ■ You could feed the horse an additional 5 pounds of grass hay, which will pro- vide about 4-4.5 Mcals per day. There- fore, it would take around 100 days for the horse to move up one BCS. ■ You could feed the horse the minimum serving of a higher calorie feed, such as a senior or performance feed (about 6 pounds is a common minimum daily serving, says Thunes). Then it might only take 45 days to move up one BCS as the horse consumes around an addi- tional 9 Mcals per day (this could differ based on individual feed formulation). The NRC has created a table (see be- low) showing how much time it takes for a horse to go from 4 to 5 on the Henneke scale, based on how much additional DE he's consuming above maintenance. Forage Comes First When changing a horse's diet, Thunes takes a forage-first approach, which is the safest way to put on weight. Because alfalfa provides more calories per pound than grass hay, she says owners can switch up to 25% of their hay to alfalfa. "If this does not do the trick, feeds using fiber sources like beet pulp and soy- bean hulls are a good option, as these are still fiber but higher in calories," she says. Mueller has found that owners are more willing to change their feed or their supplements than their forage, simply because of availability and/or growing conditions. "A more cost-effective route may be to spend a little more money on your hay versus spending a lot more money on feed, if you have another hay type or quality available to you," he adds. Mueller says he might suggest owners in regions where bermuda hay is prevalent switch to a cool-season grass hay (e.g., orchardgrass, bromegrass), which will provide more calories per pound. Add Fat and Carbohydrates Next If you can't achieve weight gain with pasture or hay and other fiber sources alone, Thunes recommends adding something more calorically dense to the diet or substituting some of the forage with a new feed. "Concentrate feeds that are higher in fermentable fiber, fat, and/ or starch are going to be more calorically dense than most hays," she says. Mueller always asks owners about their horses' temperaments, because calories from a starch source can hype up a horse, which might not be desirable for an already-excitable animal. He adds that he might, however, use a higher starch- or sugar-based carbohydrate source of calories to add weight to a horse that does high-intensity bursts of speed in competition—roping, barrel racing, short- distance racehorses, etc.—because they need this type of energy source. For more excitable horses, instead of starch Mueller adds a fat source such as oil. He prefers flaxseed or soy oil versus canola or corn oil because the latter two have poorer omega-3 to omega-6 ratios, which can increase inflammation in the NUTRITION Ideally, a horse should score between a 4 and 6 (this horse is a 5) on the Henneke body condition scale (TheHorse.com/30154), meaning you can feel but not see his ribs. DR. ROBIN PETERSON Estimated increase in digestible energy (DE) intake necessary to change the condition score of a 500-kg (1,100-lb) horse from 4 to 5 Time Period to Accomplish Gain DE Above Maintenance (Mcal/d) Percent Increase in DE Above Maintenance 60 days 5.3-6.7 32-41% 90 days 3.6-4.4 22-27% 120 days 2.7-3.3 16-21% 150 days 2.1-2.7 13-16% 180 days 1.8-2.2 11-14% Assumptions: 1 unit of change of condition score requires 16-20 kg of gain, and 1 kg gain requires 20 Mcal DE above maintenance.

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