Question
I have a nine-year-old, 16-hand (163 cm) appendix Quarter Horse gelding that weighs about 1,300 lb (590 kg). He has been diagnosed with chronic kidney failure after noticeable weight loss on an unchanging diet. His creatinine level was 3.5 mg/dL on the most recent testing. He receives a diet of orchardgrass/bromegrass hay, timothy pellets, ground flaxseed, and vitamin E. Right now, since the diagnosis, he and I go on easy trail rides a few times a week. What is an appropriate diet for a horse with this condition?
Answer
When faced with horses with chronic renal failure (CRF), researchers and veterinarians believe that nutritional changes may be most effective, and life-prolonging, for horses when creatinine levels are between 2 and 5 mg/dL. Two key management points are maintaining appetite and reducing surplus levels of dietary components that require filtration and elimination by the kidneys.
Knowing the gelding has an estimated body weight of 1,300 lb (590 kg) helps enormously in estimating nutrient requirements and comparing those requirements with current intake. Protein and certain minerals are of particular interest in formulating diets for horses with CRF.
Protein. Nutrient Requirements of Horses, published by the National Research Council (NRC) in 2007, lists the daily crude protein requirement for horses at maintenance (no work) or those in light work (trail riding) as 756 to 839 g for a 1320-lb (600-kg) horse. Mature horses can easily meet their crude protein requirement on a diet consisting of good-quality grass pasture or grass hay, so it would be nearly impossible to achieve this minimal protein intake on a weight-gain diet.
Horses suffering from CRF should have a protein intake of 10-12% of the total diet; this is greater than the NRC’s recommendation but more closely matches the amount of protein supplied by a diet consisting of good-quality grass hay (Jarvis, Veterinary Clinics of North America: Clinical Nutrition). Excessive restriction of dietary protein is not recommended, as typically feedstuffs that are low in protein (<10%) are generally also low in dietary energy and poorly digested by the horse. Diets especially low in protein can be deficient in digestible energy, resulting in weight loss and muscle-wasting.
High-protein feedstuffs, like legume forages and soybean meal, should be avoided as these can lead to dietary protein intakes in excess of the horse’s requirements. Small amounts of alfalfa (lucerne) can be fed when the horse is losing its appetite, as it is better for a horse to eat something in instances of inappetence even if it is higher in protein. Limiting dietary protein is thought to have a protective effect on renal function and minimizes the production of urea and other nitrogenous wastes.
Minerals. Providing a reference range for calcium is a little harder. Your gelding’s total diet does not contain excess calcium, though the literature does not specify what is considered the safe upper limit for horses with CRF. Typically, good-quality grass hays contain enough calcium to meet or not excessively exceed the recommended daily calcium requirement set by the NRC. To maintain a tolerable daily calcium intake level, the inclusion of large amounts of forages and feeds that have calcium levels greater than 0.5% should be avoided, if possible. Feedstuffs considered high in calcium, such as alfalfa and beet pulp, have a calcium content of 1% or more.
To provide the essential trace minerals, such as copper, zinc, and selenium, that cannot be provided by forage alone, I recommend feeding a trace mineral block or supplement that does not have added calcium or phosphorus.
Provision of electrolytes was once thought to stimulate increased water intake and urination, though recently it has been advised to avoid supplementing salt and electrolytes above maintenance needs. Forage is often deficient in sodium, so some supplementation with a salt-containing product, like commercial feeds, table salt, or electrolytes, is needed to meet maintenance requirements.
Based on the hay analysis provided, your gelding would need to receive 0.5-1 oz of salt daily to meet his sodium requirement when just offered hay and pasture. Studies have shown that horses will voluntarily consume 1-2 oz of salt per day when they have free-choice access. Some horses may consume much greater amounts, and in these cases this method of free-choice electrolyte supplementation is not recommended for horses with CRF.
Feeding a vitamin and mineral supplement that does not have added salt is an alternative option and will provide these essential vitamins and minerals; however, selecting a product with low calcium is important as not to add too much dietary calcium. Reducing the magnitude of hypercalcemia can only be done by reducing the amount of dietary calcium.
Current diet and recommendations. With that information in mind, let’s take a closer look at the gelding’s current diet.
Orchardgrass/bromegrass hay and timothy pellets are appropriate forage selections. This hay, when fed on a free-choice basis of at least 2% of his body weight (26.4 lb, 12 kg), provides just over 12% of crude protein of the total diet, if he was just receiving this hay. The guaranteed analysis for the timothy pellets is no less than 10% crude protein; however, if the actual value is less than the crude protein in the hay, you may increase the amount of pellets offered in order to reduce the total amount of protein in his diet, closer to 10%. A reasonable protein range to look for when selecting hay is 8-13% crude protein on an as-fed basis. Generally, late-cut hay (mature) has a lower crude protein level than early-cut, leafy hay.
Good-quality grass pasture is the preferred feed for horses. Maximizing the gelding’s access to pasture and encouraging a greater water intake are both strongly recommended for horses suffering from CRF.
Cereal grains (corn and oats) or vegetable oil can be added to the gelding’s diet as sources of digestible energy for weight gain. Oats are a favorite feed selection and suitable for horses with CRF, particularly if they have poor appetites. Some vegetable oils are more appropriate than others based on their omega-3 and omega-6 fatty acid ratio. Soybean, canola, and coconut oil have a more favorable ratio than corn oil, but all vegetable oils will provide the same number of calories.
Current supplements, ground flaxseed (omega-3 fatty acids) and vitamin E, have been recommended to help reduce renal inflammation and decrease oxidative damage, respectively. Supplementation with oils rich in omega-3 fatty acids, such as fish oil (EO•3), can provide a concentrated source of omega-3s; however, neither oil is recommended to be fed as an energy source for weight gain. The introduction and inclusion of large amounts of fish oil (>2 oz) into horse diets should be done so with caution as it may cause some horses to go off their feed.
The addition of dietary fat requires a proportional increase in vitamin E; it is recommended that 1-1.5 IU of vitamin E be supplemented for every milliliter of oil that is added. If 0.5-1 cup of oil (118 to 236 ml) is fed, then an additional 118 to 354 IU of vitamin E needs to be provided. Natural-source vitamin E (d-alpha tocopherol) is more bioavailable to the horse than synthetic forms (dl-alpha-tocopherol). Nano•E uses advanced nanotechnology to create a rapidly available and absorbed source of vitamin E.
