Renal disease is relatively uncommon in horses but when it does occur, nutrition plays an important role in both the recovery from acute, and management of chronic, kidney failure. In the short-term it is most important to ensure intake of nutrients, whether voluntary or not, and maintain electrolyte balance. During chronic disease, maintenance of hydration status, body condition and creatinine levels are emphasized.
Acute Renal Failure
Acute kidney injury or acute renal failure (ARF), can occur at any age in otherwise healthy horses due to either injury from nephrotoxic medications or environmental toxins, or develop secondary to another issue that has caused low blood volume.
Most horses with ARF have very poor appetite and due to the metabolic effects of low energy intake, exhibit hyperglycemia and hypertriglyceridemia. This decreased intake combined with impaired amino acid uptake also leads to muscle catabolism. Therefore, the primary nutritional goal for supporting these horses through recovery is to limit the protein and energy wasting by simply keeping them eating. Provide a variety of palatable feedstuffs, especially green grass, to encourage voluntary intake. When that fails, it may be necessary to provide enteral nutrition in the short-term either through a slurry of blended Equine Senior®
horse feed or a balanced preparation such as WellSolve®
supplement. If the horse also exhibits electrolyte imbalance and is wasting sodium and chloride in the urine, offer salt water (a 0.45% NaCl solution) in addition to plain water to drink, or topdress feed with plain loose salt (10 g NaCl per 100 kg BW per day).
Chronic Kidney Disease
Most commonly, chronic kidney disease (CKD) is discovered during an evaluation for unexplained weight loss, however in performance horses the first signs may be as subtle as a poor coat or decreased performance. The goal with these horses is to improve and maintain body condition and to manage BUN levels for as long as possible. As with the acute cases, appetite is often a significant challenge and the recommendations for intake of certain nutrients must be balanced with the need for energy intake. At a certain point it is more important that he eats rather than what he eats!
Renal diets have been used with positive results in small animals for decades and recommendations for equine diets are still evolving. Protein intake should not be quite so restricted as was recommended in the past but does need to be managed to meet but not greatly exceed NRC requirements and should be monitored through BUN to creatinine ratio (values over 15 mg/dl or below 10 mg/dl indicate excessive or inadequate protein intake, respectively. Green pasture is the preferred foundation of the diet. If hay is fed, grass hay is best due to lower protein and calcium content, however if alfalfa is all the horse will accept, then it should be fed and it may stimulate the horse to be more interested in the grass hay. Quality forage plus a vitamin-mineral supplement such as Free Balance 12:12 can be an appropriate diet. More commonly though, as mentioned above, caloric intake is a challenge and supplementation with concentrates is necessary. Oats have been long favored due to their nutrient profile and palatability, but a low-protein textured feed such as Omolene® 100
is a more balanced and complete alternative. Fat supplementation can also help meet energy requirements in those without severe hyperlipidemia and there is positive data in other species supporting the benefits of omega-3 fatty acids and antioxidants (another benefit of pasture, which is a good source of both). Calcium regulation is disturbed in horses with CKD, and the goal is to meet, but not exceed, dietary requirements for calcium and phosphorus. Salt supplementation has been controversial for these horses. It may increase voluntary water intake, but the potential further damage to kidney function may negate this benefit in advanced cases. Finally, small amounts of forced exercise can help stimulate appetite and prevent muscle wasting and can be incorporated into the management plan for these horses where appropriate.
Creatinine is an important marker for the current status and prognosis of horses with CKD. When it is low to moderate, the primary nutritional consideration may be as simple as ensuring water intake. But when creatinine is high (> 5 mg/dL) long-term, the emphasis should be on supporting body condition to maintain quality of life as long as possible.
Schott, H. C. 2013. Urinary Tract Disease. In: Equine Applied and Clinical Nutrition, Ed. R. J. Geor, P. A. Harris, and M. Coenen. Saunders Elsevier, St. Louis, MO.