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.
Extension Veterinarian
Expertise
Ruminant nutrition Dairy
herd health Metabolic
disease Reproduction Nutrition
reproduction interactions Small
ruminants Llamas
and Alpaca