ASK THE NUTRITIONIST

KAREN DAVISON, PH.D., EQUINE TECHNICAL SOLUTIONS, PURINA ANIMAL NUTRITION

Ask the Nutritionist is a monthly column featuring questions answered by PhD equine nutritionists and sponsored by Purina Animal Nutrition. Have a nutrition question you want to see featured? Email Marie Rosenthal. For clinics looking for specific nutritional advice, visit purinamills.com/ask-an-expert.

What feeding program would you recommend for a sedentary, hyperinsulinemic (fasting), 14-year-old Quarter Horse, 1,235 pounds, BCS 8/9, no history of laminitis?

It’s important to educate horse owners to recognize obesity and understand the associated health risks. Teaching them to objectively evaluate their horse’s body condition can be critical for long-term success.

The goal is to achieve and maintain a more moderate 6/9 BCS. For light horse breeds, each BCS unit change represents about 45 lbs of body weight. Research suggests horses can lose 1.0 lb/day with proper diet management or 1.5 lbs/day with diet and exercise. 1 Using these guidelines, implement a diet and exercise program to achieve the target BCS within 60 to 90 days.

EXERCISE PROGRAM

The attending veterinarian should approve any exercise regimen. Exercise doesn’t need to be overly strenuous to achieve weight loss. A reasonable program could be a 10-minute walk, 30 minutes of light trotting and a 10-minute cool down. Exercise intensity and duration can gradually increase if needed. Any exercise is better than none, though, especially when insulin dysregulation (ID) is a concern.

DIET CONSIDERATIONS

The National Research Council recommends 17.0 Mcal/day digestible energy (DE) for the horse described above. Consuming 2% of his BW in moderate-quality, warm-season grass hay would supply about 18.5 Mcal/day. Since this diet and intake level would not decrease weight, hay intake would need to be restricted. The extent of the restriction depends on horse response, which can vary significantly.

A recommended approach is to gradually reduce DE intake to 70% of what has been maintaining the current condition. If needed, intake can be reduced further to induce weight loss, provided a minimum of 1% BW in forage dry matter intake (DMI) is maintained. Hay typically averages 90% DM, whereas pasture forages may be less than 40% DM.

Also, consider the level of soluble carbohydrate in the hyperinsulinemic horse’s diet. Data from controlled research is conflicting, and specific targets for starch and sugar intake are not well identified. Common recommendations for horses with ID suggest target dietary starch plus ethanol soluble carbohydrates in the range of 10 % to 12%. Note, this suggestion disregards meal size, which affects insulin response to a meal.

With no history of laminitis and the implementation of a diet and exercise program, insulin sensitivity is likely to improve. Also, if this horse eats and tolerates warm-season grass hay (typically lower in soluble carbs than other varieties), continue with the hay source and restrict access to green pasture.

However, a hay-only diet will be deficient in vitamins and minerals and likely won’t meet amino acid recommendations, even though crude protein is adequate. A ration balancer can provide the nutritional balance necessary to support lean tissue without adding significant calories. Purina® Enrich Plus® Ration Balancing Feed is low in soluble carbohydrates, and a 1-lb meal produces a low postprandial glucose and insulin response.

RECOMMENDED DIET

Restrict hay intake to 16 lbs/day and add 1.5 lbs/day of Purina® Enrich Plus® Ration Balancing Horse Feed. • Use feeders or hay nets to limit the rate of intake and extend mealtime. • Utilize Purina® Outlast® Gastric Support Supplement to help support gastric health and proper pH. • Monitor BCS and further reduce hay intake if needed, minimum of 13 to 14 lbs/day. • Use a grazing muzzle to restrict intake during pasture turnout. Horses can consume up to 50% of their daily DE requirements in just hours of grazing, so restricting turnout time may not reduce calorie intake enough for weight loss.

UPCOMING TOPICS: June: Infections July: Colic August: Lameness

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1 ME Gordon, ML Jerina, RH Raub, KA Davison, JK Young and KK Williamson. 2009. The effects of dietary manipulation and exercise on weight loss and related indices of health in horses. Comparative Exercise Physiology 6(1); 33–42

ABOUT THE AUTHOR Dr. Karen Davison, PhD, is a director and nutritionist on the Equine Technical Solutions Team at Purina Animal Nutrition. She enjoys working directly with horses and horse owners to tweak individual feeding programs to help each horse reach its true potential.