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Feeding Horses with Pituitary Pars Intermedia Dysfunction (PPID)

Mary Beth Gordon, Ph.D.

Director of Equine Research and New Product Development

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Purina Animal Nutrition

Pituitary Pars Intermedia Dysfunction (PPID) is a disease characterized by the slow, progressive degeneration of hypothalamic dopaminergic neurons, which in turn leads to adenoma formation in the pars intermedia and resultant hormonal imbalances. PPID can result in insulin dysregulation, muscle wasting, and underweight and overweight phenotypes which is why close attention to nutritional factors is important to management of the disease.

Horses diagnosed with PPID need to be closely monitored monthly for changes in body condition score, cresty neck score, body weight and musculature, to implement and adjust the feeding program. Aged horses with normal insulin regulation, good dentition and body condition scores of 5-6.5 can eat diets containing Equine Senior® or Equine Senior® Active, receive appropriate amounts of good quality hay and be turned out on pasture. Supplements such as SuperSport® and Amplify® to support musculature and body condition can be helpful in individual cases. Horses with insulin dysregulation and body condition scores of 7 or greater, should receive lower sugar/starch feeds such as WellSolve® L/S or Enrich Plus® Ration Balancer, a controlled amount of moderate quality grass hay and have limited or no access to pasture. Special considerations must be made for horses with poor dentition to include chopped hay, hay pellets, and/or soaked hay cubes to meet fiber requirements and promote digestive health.1,2,3

Pituitary Pars Intermedia Dysfunction (PPID)

Horses with PPID can have gradients of the disease, with variations in age of onset, symptomology, and treatment response. Therefore, the dietary regimens need to be individualized to match the horse’s condition. The forage, concentrate, supplement and management dynamics all need to be considered in the best interest of the individual horse. 

Healthy Weight PPID Horses with No Insulin Dysregulation

Senior horses that are not actively obese, laminitic or experiencing insulin resistance have several nutritional options. First, evaluate their body condition and dentition, including their ability to chew and digest hay. Horses with poor dentition and/or who are not thriving on typical hay can eat traditional Equine Senior® horse feed (1225 Kcal/lb), coupled with pasture, chopped hay, soaked hay cubes or other forage extenders such as Impact® Hay Stretcher or hay pellets. The goal is to meet the Senior horse’s nutrient requirements while also providing digestible forage to assist with proper gut function. For PPID horses that chew and digest hay well and may require more calories due to an active lifestyle, our Equine Senior® Active feed (1600 Kcal/lb) is a good fit. Some PPID horses struggle with muscle wasting, and supplementation with SuperSport® Amino Acid supplement (0.5 – 1.0 lb per day) is helpful for muscle maintenance. For horses that also need more overall calories and body condition, our Amplify® supplement (2000 Kcal/lb) can be top-dressed on the ration at 1.0-2.0 lbs per day to increase calories in a palatable way. 
 
Horses with PPID can have appetite challenges related to the treatment of the disease. In these cases, finding the right feed and hay while carefully monitoring disease status is key. Alfalfa hay or soaked alfalfa cubes can be more palatable for some horses and are a good option for fussy hay eaters. Traditional Equine Senior® horse feed is palatable and relatively low in fat, making it a good place to start for picky eaters.     

Healthy Weight Horses with Insulin Dysregulation

Senior horses can have active PPID with insulin dysregulation, without being overweight. In this case, if the horse does not have endocrinopathic laminitis or other overt risk factors for impending laminitis (high cresty neck score, high leptin levels, ability to gain weight rapidly), then a low sugar/starch feed coupled with an appropriate forage source is your starting point.  WellSolve® L/S horse feed is a controlled starch/sugar formula that can be provided in multiple mini meals throughout the day to provide calories and nutrition while keeping glucose and insulin response to feeding low. If the horse is an easy keeper, a ration balancing feed such as Enrich Plus® horse feed can be fed. Any horse with high insulin values should not have access to pasture and hay should be moderate quality grass hay, provided in measured amounts (1.5-2.0% body weight). It is recommended to test the hay for sugar and starch content and soak it for 60 minutes prior to feeding if the non-structural carbohydrate content is greater than 10%. 
 
Insulin resistant horses that can’t chew and digest hay should have a low sugar/starch concentrate feed such as WellSolve® L/S coupled with 1.0% body weight in low sugar/starch (<10%) chopped forage, soaked hay cubes, or hay pellets. Without the long-stem forage in the diet to provide chewing time and satiety, these products should be fed in many mini-meals of ~2lbs each. There are automatic feeders on the market that feed in small increments that can be helpful.      

Overweight PPID Horses with Insulin Dysregulation

For overweight and/or insulin resistant PPID horses, the focus should be on diligently reducing body weight and insulin levels through controlled calories, very low sugar/starch feedstuffs and exercise, if sound movement is possible for the horse. Horses with robust metabolic syndrome and/or active laminitis should be treated very conservatively to start, with no access to pasture, a measured amount of moderate quality grass hay fed after soaking, and 2 oz per day of Free Balance® 12:12 Mineral Supplement to balance out the vitamins and minerals in the diet. The hay should be offered at 1.2 – 1.5% of body weight, soaked in hot water for 30 min, or cool water for 60 min, drained and provided in sectioned amounts via a small-hole hay net to extend mealtimes. Free Balance® Mineral can be mixed with a handful of wet, non-molasses beet pulp or soaked hay cubes as a vehicle to provide the minerals. Insulin levels should be monitored monthly and body weight and body condition score should be measured every 2 weeks to gage progress. Once initial weight loss is achieved and horses are no longer actively laminitic, then a maintenance diet can be employed. A ration balancing feed such as Enrich Plus® (1500 Kcal/lb, 1 lb minimum feeding rate/day), or low-calorie feeds such as WellSolve® W/C (900 Kcal/lb) or WellSolve® L/S (1200 Kcal/lb) would be the next step. In addition, more hay can be added to the diet if the horses are losing weight rapidly and you would like to slow down the weight loss process. Once horses reach a desired weight and body condition, other suitable feeds can be an option such as Miniature Horse and Pony (1275 Kcal/lb) or Strategy® Healthy Edge® (1300 Kcal/lb). Insulin levels and body condition should be continually monitored as these horses can still change rapidly and will need prompt attention should they suddenly gain or lose weight. 

In summary, tips for managing the diets of PPID horses are:

  1. Evaluate health status to include body condition score, insulin regulation, endocrinopathic laminitis, dentition, musculature, and fat deposits. These indexes will determine if the horse needs to maintain, gain or lose weight, their ability to chew and digest hay, and the need for targeted supplementation.
  2. To feed normal weight horses with PPID that are NOT IR – Feed Equine Senior®, Equine Senior® Active or other feed with controlled starch and sugar, according to body condition score and lifestyle. If not able to chew and digest hay, provide minimum of 1.0% body weight in chopped forage, soaked hay cubes or hay pellets fed in multiple mini-meals through the day, along with appropriate concentrate feed. Control access to pasture.
  3. To feed normal weight horses with PPID that are IR – Feed WellSolve® L/S (or Enrich Plus® Ration Balancer in small meals, with a measured amount of soaked hay. If not able to chew and digest hay, provide minimum of 1.0% body weight in chopped forage, soaked hay cubes or hay pellets fed in multiple mini-meals through the day, along with appropriate concentrate feed. Prevent access to pasture.
  4. To feed overweight horses with PPID that are IR – Feed for weight loss, starting with Free Balance® Mineral during the most critical time period and then transition to WellSolve® L/S, WellSolve® W/C or Enrich Plus® Ration Balancer in small meals once the horse has stabilized. Feed a measured amount of soaked hay, in a small-hole haynet to control calories. Prevent access to pasture.
  5. To feed underweight horses with PPID that are NOT IR – Maximize quality forage intake – utilizing pasture and alfalfa/legume hays can be helpful here. Feed Equine Senior® Active horse feed and supplement with Amplify® high-fat nugget for added calories. Add SuperSport® Amino Acid supplement for horses that need muscle support. If the horse is underweight due to inability to chew and digest hay, provide minimum of 1.0% body weight in chopped forage, soaked hay cubes or hay pellets fed in multiple mini-meals through the day, along with appropriate concentrate feed and supplements.

Equine Applied and Clinical Nutrition: Health, Welfare and Performance.  Edited by R.J. Geor, P.A. Harris, M. Coenen. Textbook, Elsevier. 2013.
National Research Council. Nutrient Requirements of Horses: Sixth Revised Edition. Washington, DC: The National Academies Press, 2007.
3 Recommendations for the Diagnosis and Treatment of Pituitary Pars Intermedia Dysfunction (PPID). Equine Endocrinology Group (Schott, Andrews, Durham, Frank, Hart, Kritchevsky, McFarlane, Stewart) 2019. Available at: https://sites.tufts.edu/equineendogroup/files/2019/12/2019-PPID_EEGbooklet.pdf

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