Please note that I'm not an expert. I have no official qualifications, certifications, etc. What we know about parrot nutrition can and does change often. Your veterinarian or a nutrition expert will be better suited to answering questions about this topic.
Vitamin D3 is one of those things you will hear me harp about a lot. That's because Vitamin D3 is one of the most essential nutrients that our birds need, and in our homes, it is often hard to get. Along with Vitamin A and Calcium, it is one of the most reported deficiencies in captive parrots. It is a crucial component in the calcium-phosphorus-Vitamin D triangle. A problem, whether too much or too little, of any of these, can cause issues with the other two. Not only does it help with calcium metabolism, it is also important to cellular function, bone mineralization, and helps regulate other body functions.
Let's go over some of the popular methods of providing this important nutrient and their drawbacks.
Sunlight
Of all the methods, sunlight has almost no drawbacks, and it cannot be overdosed. Vitamin D3 is manufactured by the skin with adequate exposure to unfiltered sunlight, specifically UVB rays, which by estimates is only 3 days a week for 15 minutes at a time year round. This means sunlight that is not interrupted by a barrier such as a window or screen which filters out almost all of the UVB needed to manufacture D3. The drawback is availability. For me, even being home most of the time, I cannot get my birds outside from about October to April because of snow and cold temperatures. This means that for at least 6 months of the year my flock is not able to manufacture their own Vitamin D3.
Full Spectrum Lighting
- UVB has only been detected by meters at extremely close (6-12 inches away) proximity, which can be dangerous to birds eyes
- UVB degrades quickly, meaning that the bulb only emits those waves for up to 6 months. So while the bulb may continue to offer light, it does not offer the light type needed for D3 production.
- Long term exposure to UV lights has been shown to cause cataracts in birds, reptiles, and rats.
An interesting article that Dr. Echols paraphrased in the Facebook group Nutrition for Pets showed some insight into tortoises and Vitamin D3, which while not exactly a bird, we can assume that at least some of what is true for reptiles is true for birds:
"Today I received the latest copy of American Journal of Veterinary Research (AJVR). While I am always excited to receive such great literary works, it was the article on vitamin D and Hermann tortoises that caught my attention.
Three groups of tortoises were studied:1 group was kept outside, 1 group indoors with a UVB mercury vapor lamp and the last group indoors with a UVB fluorescent light. All other factors (temperature, time of year, diet, etc) were kept the same. The lamp and fluorescent light were used as directed by the manufacturer.
Plasma vitamin D3 levels were measured at the start and 35 days into the study. As expected, the natural sunlight group maintained their vitamin D levels throughout the study. However, the UVB lamp and fluorescent light tortoises' vitamin D levels dropped precipitously in just 35 days.
The authors concluded that at least Hermanns tortoises need sunlight equivalent to a latitude of their natural range.
This is just another study in a series of recently published papers showing the importance of unfiltered sunlight and blood vitamin D levels in captive reptiles.
Similar such studies are lacking in most other animals (except humans). However, years of clinical experience supports that many animals need some direct exposure to sun in order to maintain normal vitamin D levels."
Food
The next logical step is food. Since it is created by the body, D3 is readily found in animal foods like egg yolks, fish, liver, and cheese. Unlike mammals, birds are not able to effectively use Vitamin D2, and so a diet consisting only of vegetable matter (seeds, fruits, vegetables, soy, etc) will result in a Vitamin D deficiency. There are only two sources of vegetarian D3 that I could find: lichen, and alfalfa. Mushrooms, often cited for Vitamin D, contain only D2, and are not recommended for birds. I have also been told that certain varieties of seaweed contain D3, but as of this writing I was not able to identify any information substantiating that.
For maintenance in parrots, the recommended amount for Vitamin D3 appears to be about 600 iu per pound of food, or 1000 iu per kilogram of food. This is for any size bird currently. Additionally, birds realistically eat about 15 to 20% of their body weight in a day.
The amount of D3 in a 2.2 pound sampling of alfalfa has just 25 IU of D3, or just over 11.36 iu per pound. That is a far cry from the 600 iu per pound amount needed by our birds, and with the amount of food that they can consume, they simply would not eat enough to compensate for the small amount present.
For lichen, I was not able to find a source that wasn't manufactured into a supplement. I did learn that the kind they use is a mix of fungus and algae, and fungus are generally not recommended for feeding to birds. Additionally, some seaweeds are thought to have D3, but little information exists beyond the fact that some can cause gastrointestinal upset in people and some animals.
On the other hand, providing animal products like the above mentioned frequently enough for health brings about the risk of atherosclerosis - a hardening of the arteries which can create numerous problems, including heart disease, stroke, and death. It is true that in the wild, parrots will consume some animal products, but they also fly miles a day, which helps to counteract it. Also, just because an animal does it in the wild does not mean that it is the healthiest thing for them. It is simply a matter of survival.
Many vets agree that animal products should largely be avoided for our birds.
However, if you really do want to feed D3 via one of these foods, here are the estimated values of D3 for known foods with naturally higher amounts. Since we know that birds need 1000 IU/kg of D3, we can essentially assume that they need about 1 IU per gram of food consumed. If we use the example of my 100g quakers, and estimating that they eat about 20% of their body weight or about 20g per day, my birds would need to consume about 20 IU of Vitamin D3 a day to maintain their health.
Cod Liver Oil: 440 IU per tsp
Swordfish, cooked: 566 per 3 oz (about 85 grams)
Tuna, canned in water and drained: 154 IU per 3 oz (about 85 grams)
Beef liver, cooked: 42 IU per 3 oz (about 85 grams)
Egg yolk, large: 41 IU per egg
One of the popular things to feed parrots is egg yolk. An egg yolk from a large egg weighs approximately 18grams. To get the needed D3 one of my birds would need, he would have to eat about half of an egg yolk every day. If he eats, at most 20grams of food a day, and half an egg yolk is 9grams, this means that half of his daily intake would need to be egg yolk just to supply enough D3.
To compare, a 100g parrot would need to eat about 3 grams of swordfish (15% of the diet), 10 grams of tuna (50% of the diet), and 40 grams of beef liver (200% of the diet) to meet daily needs.
On the flip side, you could possibly provide cod liver oil, however the amount would be hard to determine. At even 1/20 of a tsp, you are looking at 27 IUs, so the chances for over supplementation of Vitamin D3, and especially Vitamin A, from this food are very real. Additionally, with the exception of capsule form, most cod liver oil is packaged in such a way (pumps, etc) that allows for oxidation and contamination of the oil. My vet gives this a hard no for the Vitamin A overdose danger alone.
So, food based sources leave much to be desired for several reasons.
Supplements
Another option is adding a Vitamin D3 supplement to your bird's diet. (If your bird is already eating vitamin enriched pellets, you should not add a separate Vitamin without consulting a vet.)
Vitamins ideally should be added to food, not water. Water tends to break down vitamins some, and it can be hard to accurately tell how much your bird has consumed. Additionally, some birds won't drink the water after it has been adulterated, and you don't want them to dehydrate!
If your bird is on a very low fat diet (very little seeds, no pellets, little nuts, etc) please note that as it is fat soluble, Vitamin D3 needs some fat in the diet in order to be properly absorbed and used.
Again, lets use the example of one of my birds, using the basis of 1000 IU/kg of food and that they eat about 20% of their 100g body weight a day, and need about 20 IU of D3 per day to reach that amount.
While doing research for this article, I found that many of the vitamins varied wildly in their values. Many also are combined with other fat soluble vitamins (which can be overdosed).
I've listed commonly found supplements here and their associated values per dose (if listed). I have marked the ones with an asterisk that only reported the overall IU/kg and not the individual dose.
These vitamins had a good amount of D3 per dose, which could be scaled up or down based on bird size:
Hagen® (Living World) Prime Supplement for Birds: 26.4 IU per 0.55g/1cc dose.
Lafeber Avi-Era Bird Vitamins: 15.6 IU per 125mg scoop
eCOTRITION Skin & Plumage Supplement for Birds: 1,550 I.U. per oz, or approx 2.6 IU per drop*
Quicko Multivitamin: 10,000 IU/k, or 10 IU per recommended serving of 1 gram*
These vitamins seemed to have a much larger dose than most birds would need on daily basis, but they recommend supplying in water as their main delivery method.
eCOTRITION Vita-Sol: 67,500 IU per oz, or approx 117 IU per drop. *
Vetafarm Soluvite-D: 250,000 IU/KG, or 1000 IU per 4 gram dose*
These vitamins did not provide exact dosing information or do not specify how much D3 is in the product, which makes it very hard to determine if they are good for your bird's needs.
Zoo Med's Avian Plus Vitamins: 115,000 IU per kg; dosage is "sprinkle" 3 times a week. Assuming 1 tsp = 1 gram, and 1/8 tsp is a sprinkle, this would make the dosage 14 IU per 125 mg*
Avitech Cal-D Solve: 75600 IU/Kg, or about 9.45 IU per 1/8 tsp or 125mg (if 1 tsp = 1 gram)*
Kaytee Molting and Conditioning for All Pet Birds: no data for D3
*Per dose amount calculated by IU/KG and dose information, not reported by manufacturer
I strongly recommend discussing vitamins with your vet, as I am no expert, but looking at these numbers, some are so low that they would be very costly to feed or possibly impossible to feed in large enough dosages that they may not be helping at all. On the other hand, some could be deadly as they do not specify how much D3 is in their product and/or do not give actual dosage information so consumers can make informed decisions.
Bottom line: supplements make it hard to know how much your bird is really getting depending on the type and delivery method, and can pose other issues if not done in conjunction with a vet. Additionally, some are so potent that they could pose a risk for overdosing, and others are fairly weak, particularly if added to water and further diluted, and could be less economical for larger birds. So, some supplements may be a good middle ground between an all fresh and a pellet diet.
Pellets
By far the easiest way to provide our birds with Vitamin D3 is in pellets. There is a reason they are so highly recommended! Pellets provide equal amounts of nutrition per bite and cover a lot of things that are missing in a seed diet, or even in a well rounded vegetable, grain, and fruit diet. They prevent a bird from only eating what they like and causing an imbalance.
Most pellets provide Vitamin D3 in the form of cholecalciferol, which is made from lanolin washed from the wool of lambs. Sometimes it is also coupled with dried egg for another D3 source. There are two pellets that I know of that do not offer a D3 source that is in line with the D3 maintenance recommendations: Goldenfeast and TOPS. As part of a diet with other pellets or supplements, or for birds that have adequate sunlight year round, these pellets are fine. However, if you are not providing sunlight or a D3 supplement, your bird should be on pelleted diet that includes this nutrient.
The drawback: It IS a fat soluble vitamin, which means not only is some fat needed in the diet to effectively use it, but it also is stored in the body. It CAN build up in the body and cause an overdose. However, with pellets, this is actually QUITE hard for your bird to do.
One pellet that does publish its vitamin breakdown is Mazuri. For their small bird maintenance blend, they state that they have 1710 iu of Vitamin D3 per kg, which is 70% higher than the 1000 iu for maintenance I spoke to earlier. However, they also recommend up to 20% supplemented food. So, if you fed 80% Mazuri pellets, your bird would be regularly consuming approximately 1368 iu/kg of food, just 30% higher than the recommendation for maintenance.
The estimate is that D3 does not become problematic until levels 3 to 5 times necessary are routinely given. So, the diet would have to include 3000 to 5000 iu per kg of food to begin to be toxic. The Mazuri pellets, with or without other foods, is still well within acceptable limits for dietary Vitamin D3.
To go even further, parrots tend to eat about 15-20% of their body weight in a day. My quakers weigh about 100g each, which means they eat up to 20 grams a day. In order for them to eat a toxic level of Vitamin D3 from this pellet, it would need to be the only food in the diet (no fresh veggies, etc), and they would each need to eat about 35 grams or 35% of their body weight to reach a level of 3000 iu/kg in their diet. That's almost double of the amount of food they can physically eat!
So if you are concerned about overdose, simply feed the pellet at a lower percentage. I tend to feed about 50-60% pellets and 35-45% fresh foods, with 5% left over for seeds or treats. With Mazuri, my birds would then only be eating 855 -1026 iu/kg of Vitamin D3, which not only falls into safe levels, but is actually a little below maintenance levels if only fed as half the diet.
It is worth noting too, that if your bird is eating a D3 supplement and then gets sunlight, the sunlight will not cause an overdose. The body will only make up to what it needs and will stop producing when it has enough stored. So I can safely take my quakers outside in the summer and let them soak up that UVB without worrying about how many pellets they had that day!
The drawback with pellets, is that they are quite dry which can be hard on the kidneys, and they sometimes have less than desirable ingredients. Sugars and dyes are probably best avoided, and some of them use controversial forms of supplements, like Menadione. Some consumers also think that pellets should be all the bird eats, and that's simply not true. Most of the pellet companies agree that some supplementation with fresh veggies and fruits is preferred.
Additionally, some people shy away from pellets because of issues with corn or soy. There are three pellets that provide D3 that I am aware of that are soy and corn free:
Hagen Alternative Formula (no sweetener or dyes)
Caitec Ovenfresh Bites (no sweetener or dyes)
FM Brown's Tropical Carnival ZOO-VITAL Rice-Based Pellet (sweetened and dyed)
You can see all pellets that I am aware of in the U.S. here.
Bottom Line: Since pellets would be very hard to overdose on, have been developed by some of the most well respected names in avian nutrition, and they don't allow your bird to pick and choose, they are one of the easiest and safest options for supplementing D3. On the other hand, some of them do contain ingredients that may be harmful in different ways.
Conclusion
At the end of the day, we all have to do what we feel is best for our birds, but we should do so armed with knowledge. I understand some people do not like pellets or vitamins, and they find ways around this. I admire that but I also caution you to not immediately suggest pellets or vitamins are bad for every situation. For some birds, pellets simply are the best way to get the nutrition they need.
I know that I personally cannot adequately provide enough D3 or opportunities for my birds to make their own to be truly healthy. For this reason, I do feed pellets. I do not feel lazy for doing so; I feel that I have poured countless hours and more money than I'd like to admit trying to ensure that my birds have the best possible diet available to them.