What Are Some Signs Of A Wildlife Vitamin Deficiency?

Ron Hines DVM PhD

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The Fat Soluble Vitamins A,D,E & K:

These are the four vitamins which dissolve in oil or fat but not in water. For wildlife to obtain adequate absorption of these four vitamins, their food need to contain a minimum of 1.5 % fat or oil. In commercially prepared animal foods for plant-eating animals, it is often soybean oil that is added. Because the fat content of diets designed for carnivorous animals it is much higher, for them it is not a problem. Many carnivore diets contain a minimum of 20% fat. That is not done to just to increase fat soluble vitamin absorption. It is done because the metabolic need for dietary fat is much greater in carnivores and omnivores than in herbivores.

Vitamin A

Vitamin A is one of the four fat soluble vitamins. Fruit, berry and plant eating mammals and birds or animals that include them in a mixed diet  (omnivores) are efficient in converting the plentiful beta-carotenes (pro-vitamin A compounds) found in many plants into active vitamin A (retinoic acid and retinal). Animals that eat primarily meat or fish appear to be less efficient in converting those carotenes into vitamin A. They rely on eating the livers of their prey – a rich source of active vitamin A. Sweet potatoes, spinach, broccoli, squash and alfalfa are vegetables with large amounts of beta-carotene. So are most supermarket brightly colored fruit and the wild berries and fruit that wildlife normally consume. Wheat, oats, corn, millet, peanuts, sunflower and safflower seeds contain very little beta carotene.  None contain any of the active forms of vitamin A ( retinoic acid and retinal ). Those can only be obtained from fish liver oil, egg yolk, and milk products. As I mentioned, because vitamin A is only soluble in fat, there must be sufficient fat (oil) in the animal’s diet for it to be successfully absorbed. Vitamin A has many less known and less understood functions. For example, adequate amounts of active vitamin A are required for songbirds to learn their species songs properly. ( read here & here )

Dog foods rely on added carotenoids to provide dogs with sufficient pro-vitamin A/carotenoid compounds. But since all felines have lost their ability to convert carotenes into vitamin A, cat food relies on the addition of liver which is rich in active vitamin A retinol to meet feline needs. Vision problems and an increases susceptibility to respiratory tract infections have been associated with a vitamin A deficiency. Vitamin A is also necessary to maintain healthy air sac, lung and digestive tract linings in birds. So some associate an increased risk of aspergillosis in raptors and other birds with diets that are deficient in vitamin A. Preen gland impactions and lack of preen gland feather oils have also been associated with a vitamin A deficiency. In mammals, a lack of sufficient vitamin A (hypovitaminosis A) has been associated with increased susceptibility to infections, slow growth, diarrhea and blindness. Those vitamin deficiencies can be present at birth if the youngster’s mother was also deficient in vitamin A. Birds, reptiles and mammals that feed primarily on insects in the wild seem particularly susceptible to vitamin A deficiencies when kept in captivity. Animal nutritionists and veterinarians do not know why. That is one of the reasons (along with calcium) why many wildlife rehabilitators feed vitamin-mineral supplement powers (“gut loaded”) or sprinkled (“dusted”) mealworms, crickets and other readily-available insects before offering them to the wildlife they care for.  

The heat required to manufacture commercial animal diets destroys a sizable amount of the natural vitamin A it contained. So the manufactures generally add various vitamins including A, D3 and E in excess (but not toxic) amounts. Vitamin A is stored in the animal’s liver. Receiving too much vitamin A can cause liver destruction (hepatotoxicity). Another affect of long-term excessive vitamin A consumption is joint pain, joint problems and arthritis. The most common nutritional cause of hepatotoxicity in domestic animals and captive wildlife is being fed too much organ meat. But the problem occasionally occurs when a math mistake is made at the factory that produced the diet or at the manufacturer of the vitamin “premix” that was used.  It also occasionally occurs when reptiles that are suspected of hypovitaminosis A (too little A) are given excessive amounts of multivitamins in an attempt to cure them. While plant-eating turtles like red-eared sliders are capable of synthesizing vitamin A from the carotenoids in the plants they eat, meat-eating turtles and box turtles are less efficient at doing so.

Vitamin D-3

Vitamin D is actually a large group of similar fat soluble vitamins. Theoretically, wildlife need no vitamin D supplementation if their diet includes sufficient plant or animal-derived oils because those oils can be converted into vitamin D in their livers. However for skin conversion to the active D compound, D-3, exposure to natural sunlight or full spectrum indoor lighting is required. Vitamin D-3 is one of the regulators of calcium and phosphorus levels throughout the body. Calcium and phosphorus are the primary structural minerals of bone and are also essential for many of the processes that occur within all cells. We know that humans, rodents, horses, cattle, pigs and sheep can synthesize all the vitamin D3 they require from cholesterol. If any wildlife lack that ability is unknown. A lack of vitamin D or the consumption of an improper ratio of calcium to phosphorus are the most common causes of rickets  (abnormally soft bones) that occurs across the animal kingdom. To produce adequate vitamin D3, the light you provide the wildlife you care for needs to be artificial full spectrum light or natural sunlight. We humans can survive on vitamin D 2 . But most animals require theirs to be vitamin D-3. Egg yolk is a particularly good source of vitamin D3. Carnivorous fish (fish high on the food chain) are also good sources of vitamin D3. But even whole tilapia contains sizable amounts of vitamin D3. Forty minutes of normal cooking temperature destroys about a third of the vitamin D originally present in your dietary ingredients. As with vitamin A, too much vitamin D intake is also toxic. Vitamin D affects where calcium is deposited. When overdosed, calcium (mineralization) can destroy the kidneys. Deposits can also form in the joints, heart and blood vessels of animals. 

It may not only be thiaminase that is a risk factor when birds and mammals are fed fish. A 2020 report from a California bird rescue center found a possible association of leg fractures in herons and egrets with their switch from feeding herons and egrets primarily smelt in 2017 to capelin in 2018. They also received Mazuri’s Auklet supplement, which contained plenty of thiamine – but no vitamin D-3. The report had limitations. The authors didn’t measure the vitamin D-3 content of the capelin to confirm that it was low or if the birds with this problem had low vitamin D-3 levels. They also did not reported if the problem resolved when the bird’s diet was altered to a different fish(es) in following years. Too rapid a growth rate can also result in similar leg abnormalities.

Vitamin E

Vitamin E exists as eight similar tocopherols. Vitamin E is an antioxidant that helps protect the cells of all animals from destructive oxidation metabolites formed during normal metabolism. Fresh diets fed at wildlife rehabilitation centers are unlikely to be deficient in vitamin E. It is found in adequate amounts in eggs, vegetable oils, nuts, sweet pepper, turnip greens, pet foods, etc. The problem comes when any of those ingredients become stale. Staleness/rancidity (lipid peroxidation) destroys vitamin E. 

Lipid peroxidation and the lack of vitamin E can also be a problem in wildlife fed fish and other seafood. That is because the fish that are fed to fish-eating wildlife are often the lower cost ones that sat too long on the dock.  As the oil and fat in those fish becomes rancid, the vitamin E in them is destroyed. When you see tocopherols as an ingredient in commercial animal food it is there in larger than needed amounts to act as an antioxidant and preservative. Consuming excessive amounts of vitamin E can be one cause of bleeding because the vitamin also has anti-blood clotting properties. Insufficient dietary vitamin E is known to cause white muscle disease in woodchucks and deer – particularly when their selenium consumption is also low. Because vitamin E enters the animal’s body dissolved in fat, diets too low in fat and oil tend to magnify vitamin E deficiencies. That is thought to occasionally cause E-deficiency signs in raptors. 

Vitamin K

Vitamin K deficiencies are not a problem in wildlife – unless they have consumed dying rodents that consumed anticoagulant rodent baits ( eg brodifacoum or bromadiolone). In those cases injections of menadione , an  analog of vitamin K, occasionally saves them. Vitamin K deficiencies are rare in wildlife rehabilitation because the bacteria normally present in the intestines of birds and mammals produce sufficient amounts of natural vitamin K. Like the other fat soluble vitamins, vitamin K requires fat or oil to be present in the animal’s intestine for the vitamin to be absorbed. In California, 79% of fishers, 78% of mountain lions, 84% of kit foxes and 92% of raptors were found to have been exposed to the vitamin K-destroying compounds in rodent bait. The highest levels tend to be found in great horned owls. The predominant signs are subcutaneous hemorrhage or free blood in the body cavity. 

Because of concerns that children might consume anticoagulant rat and mouse poison, the EPA demanded that those type of poisons be phased out. They recommended bromethalin as a safer choice. However bromethalin works in a different way. It destroys the ability of the animal’s brain to obtain oxygen causing brain swelling. That results in tremors, incoordination and convulsions. That can occur within 4 hours of a bromethalin-poisoned rodent being consumed. I have seen many owls and raptors with incoordination that I suspect was the result of bromethalin. Although the EPA says that these effects can be temporary, I have never had any predatory bird showing those symptoms recover. There is no known antidote. 

The Water Soluble Vitamins:

Vitamin C

Vitamin C ( ascorbic acid ) is a water soluble vitamin. It is involved in tissue growth and repair. Vitamin C also functions as an antioxidant to block the damage caused by free radicals.  Most animals manufacture their own vitamin C from the glucose or galactose present in their bodies. That conversion occurs in their liver or kidneys depending on the species. All animals require vitamin C; but only us humans, bony fish, monkeys, guinea pigs and certain birds have lost the ability to synthesize it for themselves. New and Old World bats have a reduced ability to do so. Geese, swans, owls, coots, pigeons, sparrows, birds of prey, herons, crows and ravens are among the birds that synthesize their own vitamin C. Whereas shrikes, flycatchers, swallows and warblers appear to have lost that ability. Read more about that here.  Unfortunately vitamin C is a very fragile vitamin. It is easily oxidized and destroyed over time. Vitamin C is also destroyed by heat or sunlight. That is another reason why you should not store your wildlife diet ingredients, meant for animals that cannot produce their own vitamin C, for more than a month or two and why your storage area should be cool.

The B Vitamins

The B vitamins are also a water soluble group. Wildlife like deer, woodchucks and rabbits that, as adults, subsist primarily on plants are particularly susceptible to water soluble vitamin deficiencies in their weaning period. That is because they are in the process of shifting from a diet of mother’s milk that contains sufficient B vitamins to one that relies on their rumen or cecal bacterial to provide the B vitamins their bodies require. During the transition period, the bacterial fermentation in those organs may not be great enough to supply their B vitamin needs. Those needs are quite high because they are still rapidly growing. When B vitamins are purchased as a supplement, they are generally sold in a mixture that contains all of them and is labeled B-complex

Vitamin B-1 (aka Thiamine)

Vitamin B-1 or thiamine  is a water soluble B vitamin. It is required in all animals for nerves to function properly. So many foods containing animal and plant ingredients contain vitamin B-1 that a lack of it has never been reported to occur in wildlife. However, some of the fish commonly fed to fish-eating birds and mammals at zoos and wildlife rehabilitation facilities contain thiaminase , an enzyme that destroys thiamine. Raspberries, blackberries and cherries are also reported to contain thiaminase. But if there is enough of it to be of any consequence to the wildlife consuming them remains unknown. In animals that consume primarily coarse grass and plant roughage, a thiamine deficiency has been associated with feeding them too rich a diet. Concentrated diets (such as alfalfa) are thought to inhibit the bacteria in their digestive tract that would normally produce thiamine.

Until veterinarians realized in the 1970s that certain fish contained high amounts of thiaminase, a lack of thiamine was a common cause of fatal seizures in captive and rehabilitating California sea lions. At about the same time, it was also causing paralysis and seizures in the fur fox and mink ranch industries. It has also been reported in otters. In those situations it was called Chastek paralysis. A fear of thiamine deficiency is the reason that marine parks and aquaria heavily fortify their diets with large amounts of thiamine and other vitamins. Large amounts of vitamin E are generally included as well because as fish spoil they liberate unhealthy free radicals .  As I mentioned earlier, the spoilage process in these fish is called lipid peroxidation . The capsules and tablets are inserted into a fish or fishes and tossed by a good pitching caretaker to specific animals. Low-end-of-the-market fish that are sold to zoos and wildlife rehabilitation centers (fish like anchovies, butterfish, capelin and herring) are all at high risk of spoilage before you receive them. Better quality fish are routed to human consumption channels for a much higher price. If fish are not packed in ice within 4 hours of their netting, bacteria begin to break down the histidine amino acids within them into toxic histamine and biogenic amines. These unwanted changes can result in scombrotoxin poisoning.

Vitamin B-2 (aka Riboflavin)

Vitamin B-2  is only present in small amounts in seeds and grains. So deficiencies in riboflavin are primarily seen in birds and small mammals that subsist primarily on seeds or corn or that are fed diets in which a major ingredient is unsupplemented soybean meal. In birds, the primary symptom of a vitamin B-2 deficiency is leg weakness (curly toe paralysis). In mammals the signs are incoordination, trembling and general muscle weakness. Some also report exaggerated reactions to sudden noises or touch (hyperesthesia). Brewers yeast is an excellent source of riboflavin/B-2.

The Vitamin B-3 Family: Niacin, Nicotinic Acid, and Nicotinamide

Like vitamin B-2, the forms of the B-3 vitamin family that occur in plants are low in availability (low digestibility). So diets that rely a lot on corn tend to be low in the B-3s unless they are supplemented with additional amounts. The signs of a niacin deficiency are the same as for a riboflavin deficiency and if either occurs, the others are probably deficient in the diet you are feeding as well. Like all of the water soluble vitamins, animals do not have the ability to store these vitamins. So symptoms of a deficiency occur rather quickly. The two most readily available natural sources of the B-3 vitamin family for wildlife rehabilitators are beef and chicken liver. The heating involved in making commercial dog and cat food destroys much of the B-3s. So manufacturers add additional amounts. Some believe that avian species differ in the amount of B-3 vitamins they require based on their ability to internally convert tryptophan into niacin. Egg white is one of the best sources of tryptophan. 

Vitamins B-5 (aka Pantothenic acid), Vitamin B-6 (aka Pyridoxine) & Vitamin B-9 (aka Folic Acid)

Deficiencies in any of them or all of them all result in retarded growth and produce symptoms indistinguishable from deficiencies in the other B vitamins already mentioned. And like the other B vitamins, “Good” bacteria present in the digestive tract of healthy mammals and birds have the ability to manufacture a portion or all of these vitamins that the animal requires. That is one of the good reasons for not giving your wildlife wards unnecessary antibiotics. Antibiotics destroy the good bacteria along with the bad ones. 

Vitamin B-12 (aka Cobalamin)

Vitamin B-12 is also produced by intestinal bacteria. But not in amounts sufficient to fulfill a carnivorous animal’s needs. For those animals, organ meat (entrails), liver and, to a lesser extent eggs, are good sources of vitamin B-12.   Plant-consuming animals like deer and rabbits obtain all of the B-12 they need from the bacteria and other organisms (archaea) in their complex stomachs or cecum. There is little or no B-12 in the plants they eat. In the wild, fish-eating birds and mammals obtain B-12 because the fish they eat – somewhere along the food chain – consumed phytoplankton that consumed vitamin B-generating aquatic bacteria.

So vitamin B-12 deficiencies in nature are uncommon. I only know of them having occurred in areas where the soils were deficient in cobalt. Cobalt is a necessary ingredient in the formation of vitamin B-12 by the “good” intestinal bacteria. However in wildlife rehabilitation situations those important bacteria might be lost. As I mentioned, antibiotics kill bacteria indiscriminately. Diets richer in nutrients than the species was designed for kill those bacteria as well. Or perhaps the animal has diarrhea or intestinal inflammation due to a high parasite load. Diarrhea and inflammation lower an animal’s ability to absorb vitamins. Veterinarians give B-12 injections to dogs and cats as an appetite stimulant. When dogs and cats aren’t eating, they are not ingesting enough B-12 and the thought was that administering B-12 might make those pets more likely to want to eat. As is the case with a lot of popular press gossip, no one has proven that one way or the other. But in the amounts given, these injections and oral supplements are harmless. I have never know of vitamin B-12 alone being given to wildlife. But because B-12 is non-toxic when the recommended human dose is scaled down to an animals body weight and metabolic rate perhaps there is a place for it. Capromorelin , mirtazapine and diazepam are much more effective appetite stimulants for wildlife. 

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