Effect of tannic acid on iron absorption in straw‐colored fruit bats (Eidolon helvum)

Abstract

Excessive absorption and subsequent storage of dietary iron has been found in a variety of captively held birds and mammals, including fruit bats. It is thought that feeding a diet that is low in iron can prevent the onset of this disease; however, manufacturing a diet with commonly available foodstuffs that contains a sufficiently low iron concentration is difficult. An alternative is to feed captive animals that may be susceptible to this disease potential iron chelators such as tannins that may bind to iron and block its absorption. Using stable isotope methods established in humans, we measured iron bioavailability in straw-colored fruit bats (Eidolon helvum) and tested whether tannic acid significantly reduced the extent of iron absorption. Regardless of dose, tannic acid significantly reduced iron absorption (by 40%) and in the absence of tannic acid, iron absorption was extensive in this species (up to 30%), more so than in humans. Species susceptible to iron storage disease may efficiently absorb iron in the gut regardless of iron status, and supplementing these species with tannic acid in captivity may provide an alternative or additional means of preventing the development of this disease.

The role of condensed tannins in ruminant animal production: advances, limitations and future directions

“…Condensed tannin-Fe complexes can effectively inhibit Fe absorption (Lavin et al, 2010;Wren et al, 2013) at levels as low as 5 g tannic acid/kg (Afsana et al, 2004). In cell culture, a 1:1 ratio of tannic acid to Fe inhibited 92% of Fe absorption (Glahn and Wortley, 2002).…”

“…Tannic acid, a hydrolisable tannin, has been shown to reduce Fe availability in weanling pig diets (Lee et al, 2010). Condensed tannins have been used effectively to inhibit iron absorption and mitigate iron overload disorder in multiple exotic species (Wood et al, 2003;Lavin et al, 2010;Lavin, 2012). A final consideration is the contribution of CTcontaining ingredients to diets.…”

Update on Iron Overload in Zoologic Species

“…12,17,31,50,53 Chiroptera Hemochromatosis is the leading cause of morbidity and mortality in captive Egyptian fruit bats (Rousettus aegyptiacus). 15,34 In Egyptian fruit bats, clinical signs characteristic of liver failure are generally not apparent until advanced stages of the disease and include icterus, weight loss and emaciation, weakness, dehydration, and ascites. 15,34 In Egyptian fruit bats, clinical signs characteristic of liver failure are generally not apparent until advanced stages of the disease and include icterus, weight loss and emaciation, weakness, dehydration, and ascites.…”

“…10,40,60,72 Hidden sources of extra iron include other minerals such as dicalcium phosphate and drinking water. 33,34,58,60,63,72 This was shown to be effective in lemurs by following %TS. Periodic removal of commercial pellets (for 30 days once or twice a year) from the diet decreased iron analytes in birds of paradise.…”

Chiroptera (Bats)

“…Alternatively, the presence of these metals may competitively inhibit ferrous ion transport. 23,25,40 Monitoring and treatment of iron storage disease is an important aspect of captive management of frugivorous bats. Although histopathology is the gold standard for the diagnosis of hemochromatosis, less invasive methods such as use of blood parameters may also be used to monitor the development of iron storage disease.…”