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 Veterinary
surgeons made a significant discovery that might have solved the
mystery of why it's so difficult to keep the endangered black rhinos
in captivity. Even though the numbers of rhinos that live in the
wild has risen, the black rhino species has remained sparse. This
makes preserving the future species of the rhinos that much more
critical.
Concerns have been raised over the high number of black rhinos
kept in American zoos that have died prematurely of chronic anemia.
Symptoms of anemia in the rhinos include low blood cell counts,
weakness, apathy and the passing of blood in the urine, which usually
occurs just before they die. Unlike the causes of anemia in humans
such as low levels of iron, the cause of the disease in rhinos is
just the opposite, high levels of iron. Researchers were surprised
to find that the blood cells of black rhinos had 50 times more tyrosine
than the red blood cells of humans.
It is believed that tyrosine works to stop the buildup of iron
by absorbing oxygen free radicals.
Researchers also investigated the type of food rhinos ate in the
wild and found that acacia, a common food rhinos consume, contained
higher traces of iron than plants such as grasses. Although it hasn't
been confirmed, researchers also believed that the natural food
rhinos consume might be filled with higher amounts of tyrosine.
Based on these findings, researchers concluded that rhinos kept
in captivity were getting double the effects of iron due to the
iron in the feed given to them combined with a lowered capability
to counter the effects of tyrosine.
As a way to combat the excess iron problem, veterinarians have
been adding tannins to black rhino feed.
Comparative
Biochemistry and Physiology May 2004;138(1):105-9
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