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Discussion Starter #1 (Edited)
Vitamin D3 is an essential nutrient that plays a vital role in calcium absorption. But the body acquires this vitamin in an unusual way, which means that it can sometimes be difficult to provide this vitamin to our birds.

Sunshine

Wild birds get their vitamin D primarily through a biochemical reaction with sunlight. When the bird preens, it puts oil from the uropygial gland on its feathers. This oil contains a vitamin D precursor which is converted to a weak form of vitamin D3 by ultraviolet (UV) light from the sun. The bird ingests the precursor (cholecalciferol) during preening and it is converted to true vitamin D3 (1,25-dihydroxycholecalciferol) in the body.

When sunlight passes through window glass and window screens they filter out most of the ultraviolet, so sunshine that passes through a window will not help our birds produce the vitamin D they need. Direct unfiltered sunlight is required.

It's hard to find information on how much sunlight a bird needs for vitamin D production, but the recommendations seem to range from 30 minutes a week to 30 minutes a day.

Use sensible precautions when giving your bird sunlight. Avoid temperatures that are too hot or too cold, and always provide a shady spot that your bird can retreat to if it's uncomfortable. Guard against hazards like escapes, predators, and exposure to germs and dangerous objects.

It's difficult for many pet owners to give their birds enough exposure to natural sunlight to meet their vitamin D3 needs. But fortunately there are other ways to provide it.

Diet

Poultry industry practices have proved that dietary sources of vitamin D3 are a very effective way to provide this vital nutrient. But there aren't very many natural food sources of vitamin D3 - mostly certain types of fish oil, liver, eggs, and fortified foods like milk. Egg is the only item on that list that is normally offered to birds, and the amount of egg in the diet should be limited to avoid problems from excessive amounts of cholesterol, fat, and protein.

But pellets and Nutriberries are an excellent dietary source of vitamin D3. These manufactured processed foods are designed to be nutritionally complete, and will provide adequate D3 if your bird is willing to eat a sufficient quantity of them.

Vitamin D2 is found in plant sources including the grains and seeds that make up much of the diet of species including cockatiels, budgies, and conures. But this form of the vitamin is not utilized well by birds.

Caution must be used with dietary D3 supplements. It is impossible to overdose with light-based D3 sources. But supplemental (dietary) D3 is a fat soluble vitamin, which means that amounts that are not used immediately are stored in the body. If fed in excess it can lead to vitamin toxicity and can contribute to hypercalcemia (too much calcium in the blood), which affects the heart, liver, kidneys and other organs, and contributes to gout. Pellets and Nutriberries already contain appropriate amounts of D3 and calcium, and if you are feeding these foods you should never give vitamin supplements containing D3, calcium, or other overdose-prone nutrients.

It's all right to provide a calcium source such as cuttlebone or mineral block to birds with a varied diet (seeds, vegetables, less than 50% pellets), and to provide bird-safe levels of UVB light in addition to dietary sources of vitamin D.

Full Spectrum Lighting

Full spectrum lighting provides ultraviolet light and is generally believed to be a good substitute for natural sunlight. But its usefulness for birds has not been documented scientifically, and there are some questions about its effectiveness for vitamin D purposes. So it would be wise to use it in conjunction with proven sources (sunlight and/or diet) to help assure that your bird's vitamin D needs are being met. The possible benefits of FS lighting go well beyond the vitamin D issue, so it should be considered for indoor birds even if their vitamin D needs are being met in other ways.

The UVB issue. Ultraviolet light is divided into three subcategories: lower wavelength UVA, middle wavelength UVB, and higher wavelength UVC. UVB is the wavelength involved in vitamin D synthesis.

Dr. Patrick Thrush is generally considered to be the leading authority on birds and lighting, so his opinions will be extensively considered here. However, he did his work in the 1990s so it may be somewhat outdated at this time - see his website at http://web.archive.org/web/20080318214648/http://users.mis.net/~pthrush/lighting/ for a full list of articles. His doctorate is in sociology and he is/was a professor at the University of Kentucky, so he did his work on birds and lighting as an interested amateur not a professional scientist. But his work is respected and several of his articles appeared in the NCS (National Cockatiel Society) Journal. The articles most relevant to the current discussion are:

(Links may take a few seconds to go through)
The Ultraviolet Myth http://web.archive.org/web/20051109152749/http:/www.users.mis.net/~pthrush/lighting/uvmyth.html
Lighting and Your Bird http://web.archive.org/web/20080207010024/http:/users.mis.net/~pthrush/lighting/ncsj1.html
Why Use Artificial Light http://web.archive.org/web/20080202175108/http:/users.mis.net/~pthrush/lighting/whyuse.html
Bird Lighting Hotspots http://web.archive.org/web/200802061.../hotspots.html
Are Vita-Lites for Real http://faq-bmw.vancouver.bc.ca/520/are-vita-lites-for-real-187140.html
Light Right/Using FS Lighting with Birds http://web.archive.org/web/20090201023151/http://users.mis.net/~pthrush/lighting/spectrum.html

Dr Thrush discounts the importance of UVB for vitamin D purposes and seems to feel that the vitamin D2 from seeds is a good source of raw material if the bird also has access to dietary sources of D3. He feels that providing a consistent visually-balanced light source for birds is more important to their health and well-being than attempting to use UVB as a dietary supplement.

He believes that full spectrum lighting is important for regulating the bird's general biochemistry and metabolism and to provide an appropriate visual environment. UVA is part of the visual spectrum of birds so it makes sense that having it will contribute to their well-being.

UVA travels farther than UVB, so distance from the cage is less important for UVA purposes than it is for UVB. The ideal goal is to provide 100 lumens of intensity per meter squared, which is probably incomprehensible to the average bird owner.


Many bird owners have reported improved mood, energy, and feather color after they started using full spectrum lights, which may be due to the general similarity to natural sunlight rather than anything specifically related to UVB.

Many avian veterinarians recommend full spectrum lighting but there are some who don't think it is useful. The reason for these doubts might be the problems involved in delivering the UVB. For vitamin D3 purposes the light must be placed within two feet of the bird since the UVB doesn't travel very far, and the bulb's ability to produce UVB declines rapidly in a fairly short period of time (usually 3 to 6 months), long before there are any problems with the rest of the bulb's output.

Because the bulb has to be placed so close to the bird for UVB purposes, it is important to have an area in the cage where the bird can get out of the glare if it wants to.

What characteristics should the light have? There is a lot of conflicting information about what kind of full spectrum lighting is best for birds. But it seems to be generally agreed that the following is ideal:

It should have a CRI (color rendering index) of 90 or more, preferably 95-98. Natural sunlight has a CRI of 100.

A color temperature of 5000K is considered to be perfect but temperatures up to 5500 or so are OK. 5500K is the color temperature of the sun at noon on the equator.

The light fixture should have an electronic ballast, not magnetic, to avoid flicker problems which are invisible to humans but stressful to birds. Fluorescent light fixtures are currently manufactured with electronic ballasts because they are much more energy efficient than the old magnetic ballasts. But this changeover is fairly recent (beginning around 2002) and older fixtures might have a magnetic ballast.

Several types of light fixtures are available: fixtures that hang from the ceiling on a chain (sometimes called shop lights), standing lamps, and fixtures that clamp to the cage or sit on top of the cage. As with any electrical device, your bird should not have access to the cord. Putting the light on a timer and/or dimmer will give you easy control over the amount of artificial light your birds receive.

UVB and specialty bulbs.Once again, the subject of UVB is where it gets tricky. As mentioned earlier, the effectiveness of FS lighting in providing UVB is questionable, and some sources like the Mickaboo Companion Bird Rescue even advise against purchasing avian full spectrum bulbs because they have some UVB output (see http://confluence.mickaboo.org/download/attachments/1179693/light.pdf?version=1&modificationDate=1292710554000 ). But it is generally agreed that a UVB output of 5.0 is safe for birds, and this is the amount found in full spectrum bulbs marketed for birds.



(Out of space - article continues in the next post)
 

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Discussion Starter #2 (Edited)
Which bulb should be used? This is where it gets messy. As mentioned earlier, the effectiveness of FS lighting in providing UVB is questionable, and some sources like the Mickaboo Companion Bird Rescue at http://www.mickaboo.com/newsletter/apr10/Light.html do not advocate providing UVB at all. But it is generally agreed that a UVB output of 5.0 is safe for birds, and this is the amount found in full spectrum bulbs marketed for birds.

Dr. Thrush states that any fluorescent light with a CRI greater than 90 will meet the need for UVA. This may have been true in the 1990s, but modern high-CRI bulbs are often shielded to prevent UV emissions. Supplemental UVA can be provided with a small black light, which emits in the near UVA but does not emit UVB. Dr. Thrush says that ordinary fluorescents are deficient at the red end of the spectrum, so full spectrum fluorescents are needed to fill this need.

But some lights that call themselves full spectrum are only talking about the human visual spectrum, which is more limited than the avian visual spectrum and does not include UV. Some bulbs that call themselves daylight, sunlight, natural light, etc will also say full spectrum somewhere on the label, but this doesn't prove that they emit UVB. If you want to provide UV lighting, your best bet is to buy a bulb that explicitly promises to deliver an appropriate level of it.

It is generally agreed that long (18 inches or more) fluorescent full-spectrum tubes designed to provide UVB are effective at doing their job within the useful lifespan for this part of the output. As of 1999, short tubes and compact fluorescents were not effective at providing UVB because the short tube length didn't provide enough space for the necessary technology, and there is no subsequent information indicating that this has changed.

The major brands of full spectrum lights marketed specifically for birds are Feather Brite and ZooMed Avian Sun. The Feather Brite website states that their light has a CRI of 91 and color temperature of 5500K, as well as UVA of 4% and UVB of .05%, which is close to sunlight and appropriate for birds. As stated earlier, ZooMed does not provide information online, but other internet sources say that the Avian Sun light is 88 CRI, 7500K, no word on UVA, and 5% UVB (which is the industry's alternate way of saying .05%).

Dr Thrush advises against using reptile bulbs for birds. A reptile bulb with a UVB rating of 10.0 should definitely not be used for birds because it can burn the eyes and cause other problems. This actually happened to a forum member - you can read the thread at http://talkcockatiels.com/showthread.php?t=6686

The ZooMed company reportedly told a customer that their ReptiSun 5.0 bulb was exactly the same as their Avian Sun 5.0 bulb but this information has not been confirmed. But there is talk on the internet of reptile lights repackaged as bird lights, and if it's true it would explain why the Avian Sun apparently has a color temperature that is much higher than the 5000-5500K generally recommended for birds.

Dr. Thrush advises against aquarium lights because their color temperature of more than 6000K is good for simulating an underwater environment, but it is too blue for birds. This is also the color temperature at noon in the far northern latitudes (not our birds' natural environment!), and this is why fluorescent lights with a color temperature of 6500K are often called arctic white lights.

When considering the suitability of other types of bulbs (for example plant lights), consider the CRI, color temperature, and UV output. An ideal FS bulb for birds will have CRI of 95-98, color temperature of 5000-5500K, UVA of 4-5%, and UVB output not exceeding .05% (aka 5.0).

Standard incandescent bulbs have a CRI of 100 but their color temperature is less than 3000K and their UV output is minimal. Their output is quite different from that of natural sunlight at other frequencies too, skewing toward the red and yellow end of the spectrum and away from green and blue. Beware of so-called "daylight" bulbs - they are meant to simulate the general appearance of natural sunlight but they may not be true full-spectrum lights.

How much full spectrum light should be used? Full spectrum lighting is less powerful than natural sunlight so more exposure is needed. The recommendations vary considerably (from 1 to 12 hours a day depending on the source and the reason for using the light) but 2-4 hours seems to be most commonly recommended for small birds like cockatiels. Full spectrum bulbs are designed to mimic the noontime sun, and natural sunlight would not have this intensity for the entire day.
 
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