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Lory Nutrition

Studying the diet of wild lories can help improve the diet of lories in captivity.

By Debra McDonald, Ph.D

You learned about lory nutrition in the August 2009 issue of BIRD TALK magazine. Now learn more on how the diet of wild lories helps the diet of captive ones.

So, what are the symptoms of excess dietary vitamin A?  Hyperkeratosis is generally associated with diets low in vitamin A but is also a symptom of excess dietary vitamin A.  Excess accumulation of iron in the liver or ‘iron storage disease’ is also correlated with high dietary vitamin A.  Like vitamin C, vitamin A enhances the uptake of iron from the diet and is actually prescribed for humans with anaemia.  Wild lorikeets would not encounter vitamin A in the wild but many commercial diets contain excessively high concentrations of this vitamin.

Feather pigmentations aberrations are also evident with diets high in vitamin A.  These include a loss of green feather pigments (Figures 2 and 3), including production of oval spots (Figure 4) and black edging of otherwise green feathers (Figure 5).  Feather pigments of lorikeets are not based on dietary carotenoids such as those of canaries and finches but instead are derived from long chain polyunsaturated fatty acids.  These fatty acid precursors are highly unstable and an excess of vitamin A may compete with uptake of vitamin E, a potent antioxidant that may protect the fatty acid precursors.

 Figure 2.  Feather pigmentation loss on legs
(Click on image to enlarge)

 

Figure 3. Feather pigmentation loss on back
(Click on image to enlarge)

 

 
Figure 4.  Dark oval spots on back feathers
(Click on image to enlarge)

Figure 5.  Black edging of green feathers
(Click on image to enlarge)

 

 Wing feathers of wild lorikeet
(Click on image to enlarge)

 Wing Feathers Of Wild Lorikeets
Diets high in vitamin A are also correlated with high infertility.  Once again, membranes of spermatozoa are comprised of long chain polyunsaturated fatty acids that require antioxidant protection from vitamins such as vitamin E. As fat-soluble vitamins (A, D, E and K) all compete for similar mechanisms of uptake, an excess of dietary vitamin A might decrease the uptake of vitamin E even if adequate dietary vitamin E is provided. It is all about providing a balance of all nutrients.

So, how much vitamin A should we provide for lorikeets?  Should we provide any vitamin A at all?  Studies of cockatiels show that their vitamin A requirements can be met with the provision of provitamin A carotenoids from spirulina and it is plausible that similar diets can be provided for lorikeets.  However, many lorikeets maintained in captivity are colour mutations and studies of color-mutation canaries show a compromised capacity to convert β-carotene to vitamin A.  Without more comprehensive studies of lorikeets I would be reluctant to remove vitamin A altogether from their diet.  But are dietary requirements of other psittacines suitable?  Certainly cockatiels can be maintained on 2,000-4,000 IU vitamin A kg-1 diet (dry matter basis) but many lorikeet diets are in excess of 10,000 IU vitamin.

In conjunction with an avian vet in Australia, I evaluated the liver vitamin A concentrations of wild lorikeets and compared them with birds maintained on a variety of commercial diets in captivity.  Commercial diets contained up to 10,000 IU vitamin A (Table 3), in addition to a vitamin supplement that was periodically added to the diet. 

About 95-percent vitamin A is stored in the liver, so measures of liver vitamin A are good indicators of vitamin A status of birds.  This does not necessarily correlate well with blood concentration.  A study of liver concentrations of vitamin A of wild lorikeets showed that young birds had concentrations less than 20 mg kg-1, while adults had an average concentration of 36 mg kg-1.  These are much lower than in other wild seed-eating psittacines, with concentrations as high as 800 mg kg-1.  However, seed-eating psittacines do not have ready access to supplies of provitamin A carotenoids, so it would be expected that they would store some vitamin A in the liver for periods when there are few dietary carotenoids available.  In contrast, lorikeets have constant access to provitamin A carotenoids in the fruits that they feed on and would not have any need to store vitamin A.

Birds in the above study that were maintained on diets up to 10,000 IU kg-1 had liver concentrations over 4,000 mg kg-1, far in excess of that of wild birds.  As little as two to three weeks on commercial diets produced a liver concentration over 100 mg kg-1, with concentrations exceeding 500 mg kg-1 after 6 months.  Birds with liver concentrations over 4,000 mg kg-1 generally have severely compromised liver function and require euthanasia.  As little as 1,000 IU vitamin A kg-1 diet (dry matter basis) from egg powder was sufficient to elevate liver stores, and it might be necessary to provide only provitamin A carotenoids to lorikeets in the future.  However, more research is required before we can safely remove vitamin A completely from commercial diets and, until then, low concentrations of dietary vitamin A are recommended, with high concentrations of provitamin A carotenoids, such as spirulina a safer alternative.

 


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