EAZA Hornbill Management and Husbandry Guidelines

Fruits and vegetables used in captive hornbill diets are generally low in natural chelators
(e.g. phytates, fiber and tannins) that may play an important role in mediating absorption
of dietary iron in nature (E. Dierenfeld, Hornbill Digest Listserv 1998). Therefore, a
paucity of natural cheleators in zoo diets could also play a role in the disease in captivity.
Additionally, several studies in both mammals and birds have shown that ascorbic acid
(Vitamin C) increases iron take up (Johnston, undated). Immunological or nutritional
stress could furthermore predispose at least some birds to this disease.
A female Sunda wrinkled hornbill Aceros corrugatus at Fort Worth Zoo was successfully
treated for hemosiderosis by offering a diet primarily consisting of low-iron pellets
soaked in tea. The tannins in the tea bind the iron and prevent it from being stored in the
liver. Her feather condition and activity level improved (C. Brown, Hornbill Digest
Listserve, 1998). A study of the effect of feeding tea on avian iron levels is currently
being studied at Riverbanks Zoo, U.S.A. (Johnston, undated). However, tannins can only
bind a limited amount of iron, and are generally not viewed as the solution to iron storage
problems (G. Dorrestein, pers. comm.).
Phlebotomy (blood letting) is often used as treatment, on the premises that birds making
replacement blood will draw on iron in the liver. Practitioners usually start with removal
of 1% of blood per week, while testing to ensure that the bird does not become anaemic.
Bloodletting may be continued periodically for two or three years before complete
remission of the disease is declared (Johnston, undated). A recent study using an oral
chelator to bind iron in pigeons and chickens was inconclusive because of death of the
study subjects. Daily injection of deferoxaminemesilate (Desferal) is currently the most
reliable means to decrease the amount of stored iron. It is expected that in the future this
treatment will be available orally. It is important that effectiveness of methods used be
investigated by liver biopsies.
While there is much to be learned before this disease can be adequately prevented, there
are some steps that can be taken to try to ensure that susceptible birds take up as little iron
as possible:
- Use a low-iron (see also Section 5.1.7: Iron) and low-heavy metal diet. Sheppard
and Dierenfeld (2000) recommend a diet that contains 50-100 mg/kg iron, on a
dry matter basis. G. Dorrestein (pers. comm.) suggests that an effort should be
made to stay below 50 mg/kg (see 5.3: Diet suggestions).
- Avoid feeding items high in Vitamin C
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