Letters


Dear Parrots magazine,

Over-supplementing vitamins

I’m sure that Leslie Moran means well with her article about overdosing vitamins in pet birds but if people follow her dietary advice they will actually seriously under-dose their birds.

To support her thesis, she quotes an anecdote of two baby hand-reared parrots that were first presented to science in 1997. And since then there have been no further cases added to the literature. Vitamin overdose in cage and aviary birds is not rare - it is very, very, very rare!

The case in question was caused by a bird keeper making up his own hand-rearing food and adding a human nutrition product at completely the wrong dose! Such carelessness does not mean that avian vitamin supplements or pellets are dangerous, it just means that stupid people are dangerous! Far more pet birds die from accidents in the home every year than are going to die from vitamin overdoses in a century.

Vitamin A: I could bombard you with numbers but we would all get bored. So instead, let us just imagine that we are using the UK’s most popular vitamin/mineral supplement. To reach the lower end of the toxic range for vitamin A published in the literature, the supplement would have to be 40 percent of the bird’s food intake. No bird would eat that much white powder!

Imagine you own an African Grey eating 45 grams of food a day (dry matter basis). That means it would have to eat 16 grams of supplement a day - that’s five teaspoons! This compares with the about 0.5 grams (2 pinches) a day recommended for the product. Someone offering that much supplement to their bird would have to be both very stupid and very rich! So in a practical sense, overdosing on vitamin A is impossible.

Vitamin D3: Bizarrely the toxicity data for vitamin D is largely based on very old research on the synthetic vitamin D2. As birds cannot utilise D2, there are no avian supplements that contain this ingredient. Vitamin D3 is actually a natural occurring nutrient and is far safer than D2, so we have to question the figures quoted in the literature which hasn’t been updated for many years.

However, in the human field a huge amount of work has been going on. In fact vitamin D3 is becoming recognised as ‘the wonder supplement’. Many doctors are now recommending doses way above those previously regarded as toxic and claiming a whole host of health benefits from the prevention of cancer and heart disease to the elimination of auto-immune diseases like multiple sclerosis and rheumatoid arthritis. Even the FDA is increasing its recommended levels.

Because birds only make vitamin D3 naturally by exposing the skin to direct sunlight and because most of our pet birds are kept indoors behind glass, vitamin D deficiency is a huge risk. Supplementing this vitamin is crucial for a whole host of health issues so it is alarming to know that vitamin D deficiency in the diets of pet birds seems to be the second most common cause of malnourishment.

The diet Leslie suggests, pictured in the article, has two sources of vitamin D. A tiny amount of egg and a very small amount of commercial pellets. An African Grey would need to eat two whole eggs a day to get its recommended levels of vitamin D3 from that source. To get enough vitamin D3 from the pellet illustrated would need the pellet to be 93 percent of the diet. Clearly the diet illustrated contained only a tiny fraction of these amounts.

Vitamin C and Iron Storage disease: I cannot subscribe to the theory that excessive iron absorption caused by vitamin C is a cause of ISD. Most of the species that are susceptible are fruit eaters so have a diet with naturally high vitamin C levels. Nature has designed them to consume vitamin C! The paper quoted in last month’s article by Dr Debra McDonald (which is only a collection of possibilities and contains no scientific explanation for ISD) says, “However, not all studies support the view that excess vitamin C contributes to the development of iron storage disease in all species.” So using vitamin C and ISD as an anti supplements argument is seriously flawed.

In fact the explanation for ISD that makes most sense was proposed by the late George Smith who was very experienced avian vet. His belief was that iron is absorbed by birds only when they need it. The main use of iron in the body is for haemoglobin manufacture but that also requires an adequate amount of copper. Feed a copper deficient diet and iron is absorbed but not used, so the excess is stored in the liver. This is the only explanation for this disease that makes sense to me, yet I have never found a scientist that has pursued it. I believe that feeding an adequate copper level in the diet is the right solution for this disease, not feeding low iron and low vitamin C levels, which is completely at odds with the diets these species eat in the wild.

We have never had a reported case of ISD in a susceptible species on our standard vitamin/mineral supplements that all contain both iron and copper. Under dosing vitamins and minerals: Scary articles only serve to encourage well meaning bird keepers to malnourish their birds. Back in the mid 1990s, an American vet called Laurie Hess conducted a survey of about 135 pet birds in New York and concluded the following (compared to the recommended levels in Harrison and Harrison 1994): 27% had insufficient vitamin E in their diet, 65% had insufficient vitamin A, 83% had an inappropriate calcium to phosphorus ratio, 97% had insufficient vitamin D3 (and we should certainly raise the RDAs since this work), 98% had insufficient calcium.

These figures are nothing short of alarming and the primary diets that caused these figures were based on exactly the mixtures of fresh and human foods with a tiny amount of pellets that was recommended in last month’s article. There is nothing wrong with the core ingredients in this largely fresh food diet, so long as it is supplemented with a well designed avian vitamin/mineral/amino acid supplement. But as it is, this diet will certainly have an inappropriate calcium to phosphorus ratio (very little calcium and far too much phosphorus) and very little vitamin D3. The high starch, low methionine level of a diet like this is also likely to cause obesity, which is the most common cause of premature death in our pet birds.

Leslie Moran’s article said, “In order to prevent vitamin toxicity in your birds you must monitor levels of vitamins A, D3 and C in the diet.” I agree, and I would add calcium, magnesium and methionine to the list and probably a lot of other nutrients too. But the monitoring will actually show up under-supplementation in almost all diets that either use no supplements or are not almost 100% pellets. This suggests that Leslie has no actually practiced what she has preached. Because if she had evaluated her diet (as Laurie Hess’ research did) she would have found this diet is deficient in exactly the same nutrients, and more, that she is telling you to avoid.

Using properly designed bird supplements in conjunction with a seed and fresh food diet is a simple, safe and cost effective way to keep your birds well fed and healthy.

Malcolm Green - Birdcare Company

 


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