Zinc Deficiency Disease

Idiopathic Hyperkeratosis (Zinc-responsive Drermatosis) -  This is a thickening of the outer skin with the cause being unknown.  One of the most frustrating diseases of llamas and alpacas.  The lesions appear as a thick adhering crust most common on the sides and back areas, progressing to the thighs, forearms, abdomen, and perineum.  Wool loss occurs as the disease progresses.

Dr. LaRue Johnson recommends the following treatment in the Merck Veterinary Manual:  "1 g zinc sulfate or 24 g zinc methionine per day. Calcium supplementation should be minimized and alfalfa hay discontinued. Affected animals may be zinc responsive but not deficient."

Diagnosis is by a skin biopsy.  In personal experiences, continuous zince supplementation over many months did not produce improvement to this skin condition.   


More Information ..............................................

Zinc Responsive Dermatosis
Hyperkeratotic skin conditions in New World camelids
Sandra D. Taylor, DVM, PhD, DACVIM
Purdue University, College of Veterinary Medicine, West Lafayette, IN

Inquiries on Skin Diseases       
(article from Penn State Extension)


Question 1: Zinc Supplementation and Skin Lesions

The first inquiry is a very common one for many llama and alpaca owners, skin lesions and what to do with them. First a disclaimer, I am not a board-certified dermatologist, but the question was more about feeding zinc to address this issue. As many owners are aware, llamas and alpacas have a propensity for unusual crusts and thickened skin that seems to be responsive to zinc supplementation. However, it must be emphasized that there are many other causes of skin disease in llamas and alpacas that are not responsive to zinc.

In this particular situation, the lesions are described as hard leathery skin primarily located on the ventral abdomen, inside of the legs and on the face. This lesion distribution is consistent with a number of dermatologic conditions, including parasitic disease and idiopathic hyperkeratotic dermatosis (zinc-responsive). One question to ask is if the animal seems pruritic ("itchy"). Parasitic diseases are most typical pruritic in nature. Idiopathic hyperkeratosis is commonly seen dermatologic disease in llamas and alpacas and may comprise a number of somewhat interrelated, or different, syndromes somewhat responsive to large doses of dietary zinc. Diagnosis is best made by skin biopsy to identify the physical changes and thickening of the keratin layer.

Zinc has been associated with skin health in many different species. Classical zinc deficiency disease in pigs and other species is parakeratosis, a unique hyperkeratotic disease where the nuclei of keratin cells are retained rather than being lost. Parakeratosis in pigs and poultry has been associated with overfeeding of calcium in the diet, as calcium interferes with zinc availability in the intestine. A true zinc deficiency has not been definitively characterized with dermatologic lesions seen in llamas and alpacas, though it has been implied. A confounding issue is blood zinc concentrations in llamas and alpacas are lower than other species and they have been interpreted to be deficient. This point emphasizes the need for good llama and alpaca reference values for the proper interpretation of diagnostic tests. However, supraphysiologic doses of zinc (dietary supplementation in excess of requirements) could have a therapeutic effect, independent of a deficiency state. Role of zinc in the pathogenesis of hyperkeratotic dermatosis in llamas and alpacas remains elusive and requires further study.

In the situation at hand, I would consult with your veterinarian to ensure you do not have some other dermatologic disease process. If the diagnosis is a zinc-responsive dermatosis, then consider supplementation. The easiest method of supplementation is to find a commercial product with high zinc content. Dr. Norm Evans' llama/alpaca pellet is a good example, though there are others. Dr. LaRue Johnson has advocated a mineral mix containing 50 lb trace mineralized salt, 50 lbs steamed bone meal, 50 lb dry molasses and 10 lb zinc methionine (Zin-Pro 100) containing approximately 5500 parts per million (ppm) zinc. At an expected intake of 1 oz per day, this mineral mix provides 150 mg zinc. As you and many other owners have found out, zinc supplements are not very palatable and simple top-dressing is not always successful. One could hide the zinc supplement in a tasty treat (applesauce) and hand feed, but this is labor intensive. You could mask the supplement in your grain by adding some molasses. If only one animal is involved, these may be feasible solutions.

How much zinc is necessary and from what source? We really do not have an answer at this time to these questions. Zinc can be supplemented in inorganic (zinc carbonate, zinc oxide or zinc sulfate) or organic (zinc methionine, zinc proteinates) forms. Questions remain as to whether the organic forms are superior or if inorganic forms can be supplemented at slightly higher levels with equal response. Current recommendations are to provide 1 g zinc sulfate (364 mg zinc) or 2 (200 mg zinc) to 4 (400 mg zinc) g zinc methionine (Zn-Pro 100, 10% zinc). As one can see, there is a wide range in recommended supplement amounts, but the actual amount of elemental zinc being delivered is between 200 and 400 mg per day. Zinc delivery from the Johnson mineralisslightlylessandfromtheEvans' pellet slightly more than this range. Across all recommendations, response to daily zinc supplementation is slow, occurring over a 2 to 3 month period. If one is going to supplement at the higher rates, it is suggested that an organic zinc form be used as a large portion (40-60%) of the zinc supplement. Excessive zinc intake can interfere with other minerals (e.g., copper, iron, selenium) and may induce other disease problems. Use of organic mineral forms will reduce these negative interactions. Don't fall into the trap of: "if a little is good, a lot more is better".

Free choice mineral supplements should contain a minimum of 5,500 ppm zinc. This number can typically be found on the product label under the guaranteed analysis. Zinc content of pellet or grain supplements will depend upon amount expected to be fed and how its mineral content complements the mineral supplement, if any is to be fed. Assuming all trace minerals coming from a supplement and not a mineral mix, a reasonable zinc content for a pellet supplement to be fed at a rate of 1 lb per day would be between 440 and 880 ppm to deliver 200 and 400 mg zinc per day, respectively. Use these numbers as guidelines in evaluating possible products for use in correcting this condition. Remember, it may require up to 2 to 3 months for a response to be seen. Work with your veterinarian to determine the proper diagnosis and proceed from that point.

Robert J. Van Saun, DVM, MS, PhD        
Ruminant nutrition Dairy herd health Metabolic disease Reproduction Nutrition reproduction interactions Small ruminants Llamas and Alpaca




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