by Scott Lewis
First published in "Journal of the International Parrotlet Society," Vol. XIV, Issue 1, Jan/Feb 2005.
(Author's note: This article was originally part of a discussion on a mailing list for professional aviculturists about the pros and cons of pellets and natural foods and whether pellets caused problems, such as arteriosclerosis and gout. This article is not intended to be a complete article on psittacine diets. Instead, it relates some common-sense information based on the author's experience and readings.)
Let me preface all this by saying that I am NOT speaking out against pellets.
Pellets are a part of our psittacine diet at Old World Aviaries. I think
that pellets should be a part of psittacine diets, or a least of the diets
that most feed, to avoid deficiencies of micronutrients that may not be supplied
in sufficient quantities if pellets are eliminated from the diet. However,
it seems to me that natural components are most likely also an important
part of psittacine diets.
In human nutrition, a varied diet is recommended. Although we don't have human pellets, one might assume that we could get by with a multivitamin, maybe a mineral supplement or two, an essential amino acid supplement, and a paste that contained a proper theoretical ratio of carbohydrates, proteins, and fats. And, maybe we could.
But first, we would be bored to death. And, I think our birds are intelligent enough that even if pellets are sufficient to maintain them, they would be bored to death, too. As I recall, in a study on environmental enrichment in Amazons conducted by a major research facility, which involved adding natural food items to a pelleted diet, the researchers weren't sure if breeding success was increased as a result of the addition of fresh foods to the diet because of their nutritional benefits or simply because the fresh foods enriched the birds' environments. But, fresh foods plus pellets did increase breeding success compared to pellets alone. (Consider that for many caged birds, a variety of interesting and stimulating food items may be important from the stand point of environmental enrichment as well as nutrition. They certainly are without many of the stimuli they would have in a natural environment.)
Second, it appears to me that we find over and over that supplements that theoretically should supply the same benefits as natural foods in human diets just don't cut it. Although I can't cite articles, it appears to me that this is often because a natural source of, for example, vitamin A, actually contains a complex of related molecules of which beta carotene is just a major component. And, at least some evidence indicates that related carotenes may be important if not just as important for long-term health as the major component in vitamin-A metabolism. Perhaps, even some non-carotene molecules that are typically present in plants that produce carotenes also play a role.
In addition, I know that in some cases involving human nutrition, it has been suggested by scientific studies that too much of one form of a micronutrient may inhibit the beneficial effects of other forms of the micronutrient. For example, the least expensive vitamin E supplement is d-alpha tocopherol. However, natural sources of vitamin E typically supply a complex of tocopherols, not just the d-alpha form. Scientific studies have suggested that too much d-alpha tocopherol can inhibit the beneficial qualities of other tocopherols, which are also important in human nutrition.
I think findings such as these, about
vitamin A and vitamin E, explain why we are seeing more individual vitamin
supplements being made available as complexes of the related forms of particular
vitamins. Although, marketing and the ability to charge higher prices probably
also come into play.
By analogy, if one assumes that pellet manufacturers enrich their pellets with single forms of micronutrients, even though, for example, vitamin E may be present in sufficient quantity in theory, in fact, the benefits of the vitamin E may be reduced because a single form instead of a complex of related tocopherols is used to enrich the pellet. In contrast, natural sources of micronutrients contain complexes of micronutrients.
all I know, all of the pellet manufacturers may be using complexes of the
various micronutrients, but I doubt it. The complexes are more expensive.
However, if I am wrong about this, I apologize to the pellet manufacturers.
I think that similar arguments also could be made for micronutrients other than vitamins A and E and for the macronutrients. Not all proteins, fats, and carbohydrates are created equal. Also, consider that most pellets appear to be relatively low in dietary fiber, which is considered to be important in human diets.
Finally, obligate fructivores and nectarivores aside, the assumption that has to be made if one feeds exclusively pellets, which is that the nutritional requirements of the remaining 300-plus species of psittacines are essentially the same, is making a major leap of faith. So, we feed a varied diet that includes both pellets and natural foods and hope that, by providing a variety of foods, we are supplying the needs of our various species of birds. (Many pellet manufacturers recommend additional food items in the diet. I think even Harrison has backed off on the 100% pellet recommendation.)
As for pellets causing arteriosclerosis, gout, and other health problems, I don't know, but I really doubt that the problems are related as much to pellets per se as they are to supplying too many calories. I suspect that the main problem with pellets, if there is one, is that they are energy-dense foods that often are fed in quantities that are too high.
A cup of pellets,
especially the heavy solid extruded pellets, has a heck of a lot more calories
than a cup of produce. It probably has more calories than a cup of seed,
if you consider that a significant portion of a cup of seed is composed of
non-digestible parts of the seed (hulls and such) and that if a mix is offered,
many birds will pick out their favorite stuff and ignore the rest unless
they are starving, which ignored rest may make up a significant portion of
the seed mix. (I know that with the commercial mix I have been feeding lately,
about half the stuff in the mix goes uneaten by many of my pairs.) And, I
suspect that when pellets are supplied as a part of the diet, often they
are unintentionally over supplied. I have seen many breeders describe their
diets as this and that and "pellets always
available." Making any energy-dense food source always available is
probably a mistake with captive birds.
Consider that in nature, parrots and other flighted birds expend significant amounts of energy in the form of aerobic exercise, also known as flying, which is necessary for foraging, predator avoidance, and such. By comparison, although I know of no metrics in the literature, a pair of Amazons in an 8-foot cage surely gets a small fraction of the exercise that it would in nature. Combine that with an energy-dense food source that is always available, regardless of whether the food source is pellets or seed, and a relatively long life expectancy, and I suspect that a parrot is headed for health problems associated with obesity and insufficient exercise no matter what the food source.
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