Miscellaneous diet and health topics

Animal protein - healthy or not?

Note: this article was written specifically about parrots, but is expected to be applicable to some other species

It has been commonplace to feed animal protein to pet birds for over a century, but the practice has come under fire recently as potentially unhealthy.  Obesity and atherosclerosis are widespread health problems among pet birds, and studies have shown that we can induce atherosclerosis in birds by feeding them cholesterol (which is found in all foods from animal sources and is not found in foods from plant sources).  But the studies were conducted at the "massive overkill" level of consumption, so while they tell us that eating cholesterol can cause atherosclerosis in birds, they don't tell us anything at all about what the safe level of consumption is. 

Therefore many avian veterinarians currently recommend that animal protein should never be fed to parrots at all.  This seems like overkill in the conservative direction; although we don't know what the safe amount is, it's probably a number greater than zero. Part of the reason for this extreme recommendation is that many bird owners don't have a good sense of proportion and give their bird way too much food from animal sources. Telling these people to cut animal protein out of the diet completely is the best way to prevent overfeeding.  If we assume that the average human weighs 150 pounds, then giving a whole egg or whole chicken drumstick to a one-pound bird (like an African grey) is equivalent to giving 150 of them to a human, which is clearly excessive.  A more appropriate serving size for the bird might be a quarter teaspoon to a half teaspoon as an occasional treat.

We don't have much information on how much animal protein parrots eat in the wild; some species might not eat any at all.  If they do eat animal protein, it's expected that almost all of it would be in the form of insects, since that's the life form that would be the most easily available and the easiest for them to catch and eat. I've heard unconfirmed reports that some wild parrot species (including African greys and some Australian species) have been observed foraging on carcasses and other meat sources. The only confirmed meat-eating wild parrot species is the kea of New Zealand, which reputedly attacks sheep to eat the fat around their kidneys.  But this is an isolated example from the most remote branch of the parrot family, which can not be taken as an example of typical parrot behavior.  Wild rainbow lorikeets have been observed eating meat put out for other types of birds at feeding stations in Australia, but this is believed to be aberrant behavior in a species that primarily feeds on nectar.

The primary nutrients in food from animal sources are high-quality protein and fat (not always in that order). It's thought that the protein requirements of pet birds are about the same as those of wild birds (Koutsos et al) but their calorie requirements are dramatically different, since pet birds expend far less energy in their daily life than wild birds do.  The protein may be beneficial, but most pet birds don't need a lot of fat.

Because of all these uncertainties, I don't recommend that people feed animal protein to pet birds.  But I also don't recommend that they refrain from doing it. That's a decision that everyone needs to make for themselves.  I do recommend that if they decide to give their bird animal protein, they should do it intelligently.  Use good sense and moderation, not an all you can eat animal protein food orgy. As a general rule, foods that cause problems in excess are not associated with problems when consumption is moderate.

The trick is knowing what "moderate" means for the food in question, and we don't have any guidelines for animal protein. Most birds will happily overeat animal foods if they get the chance, so it's up to you to set a sensible limit. Your bird's long-term health could depend on it. One useful technique is to think about how big the serving would be if you scaled it up to human proportions and see whether it looks excessive or not.  Compare your weight to your bird's weight and do the math. Remember that birds don't actually need any animal protein in their diet; their protein needs can be met using the right combination of plant foods (grain + beans or legumes = complete protein) or by feeding pellets.

If food from animal sources is to be fed to parrots in a healthy way, the focus should be on providing small amounts of lean protein, avoiding high-fat parts like chicken skin and bone marrow.  Another benefit of avoiding fat is that this will help prevent the feathers from getting gunked up with grease, which destroys their insulating properties.

The rest of this article will talk about the studies on cholesterol and atherosclerosis in birds, and four main categories of food from animal sources:  egg, meat, insects, and dairy.

The cholesterol studies

Apparently there are only two studies on the link between dietary cholesterol and atherosclerosis in birds.  Finlayson and Hirchinson published a paper in 1961 describing a study in which budgies were fed a diet of 2% cholesterol. The paper doesn't say where the cholesterol came from.  Since it was 1961 and people didn't know any better, the rest of the diet consisted of millet, canary seed and oats - the classic all-seed diet. Some of the birds in the study were also fed 15% lard.

The second study by Beaufrere et al was published in 2013. They fed quaker parrots a diet of Kaytee Natural with 1% cholesterol added.  Most of the cholesterol was obtained from sheep's wool. Both studies found that the birds developed atherosclerosis within a few months. Although both studies were small, there's no reason to think that the results are misleading in any way.  Everything is bad in excess, and they were feeding cholesterol at a level where it would be surprising if the birds DIDN'T develop health problems.

What does it mean to feed cholesterol as 1 or 2 percent of the diet?  I did some calculations using cockatiels since they're my go-to bird. Most websites say cockatiels eat 1 1/2 to 2 tablespoons a day of food, and when I weighed 1 1/2 tablespoons of birdseed it came to 18 grams (that includes the shells).  I also found a site saying that cockatiels eat 15 grams of food per day, so I used that number as a conservative estimate of 100% of the diet.  If I've done the math right, 1% of that is 150 milligrams of cholesterol being given to a hypothetical test cockatiel every day, or 300 milligrams if the experimental level is 2% of the diet.

If we assume that the average cockatiel weighs 3 ounces and the average human weighs 150 pounds, then one human weighs the same as 800 cockatiels. Our hypothetical study cockatiel is eating 150 milligrams of cholesterol daily if the diet is 1% cholesterol, and the average large chicken egg contains 186 milligrams of cholesterol.  Time for some math!  (150/186) x 800 = 645.  Feeding a cockatiel a diet of 1% cholesterol is roughly equivalent to a human eating the cholesterol from 650 eggs every day.  Double that to 1300 eggs for a diet of 2% cholesterol.  The birds in both studies ate an absolutely massive amount of cholesterol every day for several months, and I doubt that it's physically possible for anyone to achieve a diet of 1% cholesterol by eating natural foods. 

The abstract for the 1961 budgie study basically says "everybody's been inducing atherosclerosis in all kinds of animals by feeding them lots of cholesterol, so we though 'hey, let's do it with birds!'" Which makes me wonder if this is how we were misled into thinking that dietary cholesterol was bad for humans, because problems were observed when unrealistic amounts of cholesterol were fed to lab animals. After a half century of warnings that humans shouldn't eat very much cholesterol, the U.S. government's Dietary Guidelines Advisory Committee declared in 2015 that cholesterol was no longer a nutrient of concern, because there's no serious evidence of a link between dietary cholesterol and heart disease in humans (Time). Will this turn out to also be true of birds?  There's no way to know. But I bet that it would cause some health problems if somebody did a study where humans were force-fed huge amounts of cholesterol every day for several months.

This 2013 paper by Beaufrere et al (the same guy who did the quaker study) conspicuously fails to mention animal protein or dietary cholesterol as a suspected cause of atherosclerosis, and recommends increased activity and avoiding dietary excess as preventive measures.

This 2004 paper by Bavelaar et al says that

"possible risk factors for atherosclerosis in parrots are age, genetics, plasma cholesterol levels, diet, inactivity, social stress and obesity.  However, only the effects of age and genetics have been clearly demonstrated in parrots".

Yet another paper by Beaufrere et al compared the blood cholesterol values for six genera of parrots.  They reported that quaker parrots had the highest level; next were Amazons, African greys, and cockatiels, whose levels were fairly similar to each other; next were the white cockatoos, and macaws had the lowest levels. These rankings correspond to the frequency of atherosclerosis in these species, so there appears to be a correlation. But what causes these cholesterol levels? The paper briefly mentions the two cholesterol studies but focuses more attention on a possible a link between atherosclerosis and fat consumption. It notes that macaws consume more fat in the wild than the other species and 

"differences observed among genera in plasma cholesterol levels and atherosclerosis prevalence are possibly associated with different fat nutritional requirements and the lipid metabolism abilities of different species, with atherosclerosis-resistant species being better 'equipped' to metabolize lipids. In captivity, parrots are given the same diet year-round, with little variability and consideration for physiologic status and season. In addition, some species may be more active and may not adapt metabolically as well as other species to the sedentary nature and the ad libitum provision of high-energy food in captivity."

Petzinger et al reported that more Omega 3 fats in the diet had a beneficial effect on the blood profile of quaker parrots.

In summary:  it has been clearly demonstrated that feeding ridiculously large amounts of cholesterol to birds can cause atherosclerosis, but we have no information on the effect of consuming moderate amounts of animal protein.  The researchers in the field don't appear to believe that cholesterol in the diet is a leading cause of atherosclerosis in captive parrots.  They cite other factors as prime suspects, including age, sex, activity level, genetics, stress levels, and the amount and type of fat in the diet.  The papers that mention the two cholesterol-feeding studies are silent on the subject of avoiding animal protein.

SOURCES OF ANIMAL PROTEIN

While reading the rest of this article, keep in mind that parrots and other commonly kept pet birds don't have any requirement for animal protein, and their nutritional needs can be met without feeding it at all. It's completely optional and we don't know the safe limit.  So if you choose to offer it, please use common sense and provide an amount that's proportional to the size of the bird.

Eggs

There's something special about eggs that makes the idea of feeding them to birds seem appealing. Eggs are nutrient dense, containing everything needed to make a complete baby bird from scratch. It's reasonable to think that some of those nutrients would also be useful for maintaining an existing bird. Eggs are frequently used as a breeding food, basically letting the parents feed the babies the same food they "ate" before they hatched. Everything in an egg came out of a bird so there isn't anything in them that would be foreign to a bird.  But you have to be careful, because the nutritional needs of a fast-growing embryo are very different than those of an adult bird.  Eggs are high in protein and many vitamins and minerals, but they're also high in fat (to fuel the growth of the embryo) and cholesterol (used in building embryonic cell walls; adult birds make their own cholesterol for this purpose and don't need it in the diet).  If you feed egg, keep the quantity small and sensible.  Remember, giving a whole egg to an African grey-sized parrot is like giving 150 eggs to a human.

Wild birds don't normally eat eggs.  It would be species suicide to eat their own eggs of course.  But they also don't seem to go around eating the eggs of other species - I've never heard of a type of bird that does this, and can't find any references to it on the internet.

Meat

Chicken is the meat that's most commonly fed to pet birds, followed by fish.  You don't often hear of people feeding beef or pork to birds.  Meat is higher in protein and lower in cholesterol than egg, but that's not a license to overdo it.  It's excessive to give a whole chicken drumstick to any parrot.  If you offer meat, keep it lean and non-greasy.  Avoid high-fat tidbits like chicken skin and bone marrow.

Insects

The nutritional value of insects is fairly similar to meat. The protein and fat content varies with the insect species; some have more protein and/or fat than conventional meat while others have less.  (The-Scientist, Slate).  Their cholesterol level will depend on what the insect has been eating (Ritter).

However there is a pitfall with insects that doesn't occur with conventional meat.  The exoskeleton of some insects contains a large amount of phosphorus, which can interfere with calcium absorption and result in calcium deficiency.  This is a well-known problem in the reptile community, and it's recommended to dust these insects with calcium or load them with calcium in some other manner prior to feeding them to reptiles (LLLReptile, DrsFoster&Smith).  Therefore appropriate caution should be used when feeding high-phosphorus insects (including mealworms and crickets) to birds.

Dairy

As far as birds are concerned, dairy products are sort of like the opposite of eggs in some ways. All bird embryos are "fed" egg prior to hatch, but no bird eats dairy products in the wild. Milk is made by mammals for mammals.  All mammals drink milk in infancy but no other animal consumes it in nature at any stage of their life.  There's plenty in it that's alien to birds, such as unusual saturated fats that are found only in milk and coconut oil. But the most alien thing in it is lactose, a sugar that makes up 2% to 8% of milk (the amount varies by mammal species and by individual).  An enzyme called lactase is required to digest this sugar, and mammals are apparently the only vertebrates that produce this enzyme because they're the only vertebrates that need it.  Most mammals (including many humans) lose the ability to produce lactase as they reach maturity, becoming lactose intolerant in the process. When a lactose-intolerant individual consumes lactose, it can produce unpleasant symptoms including gas, bloating, diarrhea, and nausea.

Birds are naturally lactose intolerant since they never had the ability to produce lactase in the first place. However this does not mean that they have zero ability to digest the lactose in milk products.  Bacteria in the gut help many animal species digest foods that they could not digest on their own, and Hamilton and Mitchelll reported that some researchers found lactase in the gut of "fowls" who were fed milk and others found it in the crop, indicating that some digestion was occurring. Douglas et al found that feeding 2 to 4 percent galactose (a component of lactose) improved the growth rate of broiler chicks. See Backyard Poultry for a more readable description of this study and a general discussion of the ins and outs of feeding dairy products to birds. In the past it was common to feed "milk sop" (bread soaked in milk) to pet birds, and a google search for milk sop birds will turn up 100-year-old references to the practice, some praising it and some condemning it.

Because of the digestibility issues, milk products are generally considered to be the least suitable form of animal protein for birds. If dairy products are offered, it's appropriate to choose the product wisely, use great restraint as far as the quantity is concerned, and to monitor your bird afterward for signs of digestive upset.  Individual birds vary in their ability to tolerate or digest lactose, just as individual humans vary.  Some might have zero tolerance, while others may have considerable tolerance. 

Dairy products vary in the amount of lactose they contain.  Milk is high in lactose so it's not a good choice for birds, and milk sop is no longer recommended by anyone. But yogurt and many cheeses are low in lactose and can be digested by many lactose-intolerant individuals (Lactose Intolerance Clearinghouse). These are currently the milk products that are most commonly fed to birds.  There's no particular disadvantage to feeding yogurt, apart from the general need for moderation and caution. Cheese is more problematic due to the high fat content.

There are unconfirmed scaremongering-style reports on the internet about cheese causing crop impaction in pet birds, but I have serious doubts about whether this is even physically possible.  Cheese is soft and does not have long stringy fibers that could tangle into a mass that's too large to pass through the system, so I fail to see what would hold it back.  There are some diseases that can more or less paralyze the digestive tract so food stops passing through the system, and it's possible that this is the actual cause of some cases of "crop impaction" that were blamed on whatever happened to be in the crop at the time.

Copyright 2015 Carolyn Tielfan all rights reserved