Vitamin A, or retinol, is a collective term for naturally occurring retinoids and those carotenoids that have retinol activity, such as beta-carotene. Retinol, the pure form of vitamin A, is only found in animal products, especially liver and eggs. In vegetables, vitamin A only appears in its precursors, usually as beta-carotene. Breast milk contains a lot of vitamin A and is the most important source for a puppy. This should be considered for bottle-fed puppies.

International Unit (IU)
changing to micrograms
Vitamin A, animal	1 IU = 0,3 µg
compared activity for vitamin A (RAE-value), beta-carotene	1 IU = 0,6 µg

Vitamin A in Brief

Vitamin A is only obtained from animal-based food. Its precursors, such as beta-carotene, are obtained from the plant world. Vitamin A is mainly stored in the liver and to some extent in fat tissue. Beta-carotene is also stored in smaller amounts in the liver, where it is converted into vitamin A. However, the conversion of beta-carotene to vitamin A is effectively regulated, and it cannot increase the body’s vitamin A levels higher, which would be desirable in some diseases and during stress.

Zinc is the most important factor in the processing of vitamin A, and a zinc deficiency also leads to a vitamin A deficiency.

Vitamin A is needed – in addition to vision

• for normal growth and development
• for the development of immunity
• for pregnancy, fertility, and sperm production
• for healthy skin
• affects several transport proteins and enzymes
• affects fat metabolism

A deficiency in vitamin A causes fertility disorders, fetal mortality, muscle weakness, mucous membrane and skin diseases, poor coat and nail condition, and night blindness. Vitamin A is also used as supportive therapy for skin problems, diarrhea, and respiratory diseases. This is because a deficiency manifests as decreased immunity, which shows as diarrhea and respiratory infections. In kennel cough, higher vitamin A in food is completely justified.

Vitamin A overdose, toxicity, is extremely rare in dogs because canines can excrete up to 60% of vitamin A and, as carnivores, they tolerate higher levels of vitamin A than humans.

Generally, without going into too much detail, the maintenance requirement for vitamin A in dogs is stated to be 75-100 IU/kgBW, which is 22.5 – 30 µg/kgBW as retinol. For a 10 kg dog, that’s 300 µg, and for a 30 kg dog, 900 µg. However, a range of 80 – 500 IU/kgBW is also used. Often, amounts for puppies are presented as 270 IU/kgBW. In diseases and stress, significantly larger doses can be used as supportive therapy.

The Chemistry of Vitamin A

In feeding, there is generally no need to worry about the different chemical forms in which vitamin A appears. It is sufficient that the analysis tells how much vitamin A is in the food or foodstuff. As is almost always the case with “active substances,” nothing is rarely in its purest form in food (or the body). They are always combined with something else, or their own chemical structure differs. The same applies to vitamin A. It’s good to know the different terms, even if they are not needed in practical life.

Retinol is the alcohol form of vitamin A. When the alcohol group is replaced with an aldehyde group, retinal (retinaldehyde) is formed, and as an acid, retinol becomes retinoic acid. Retinol esters, in turn, are retinyl esters. There are countless derivatives of vitamin A.

Formation of Vitamin A

The body forms vitamin A from carotenoids in the cells of the small intestine as needed. It is mainly stored in the liver, and those carotenoids that have not been converted into vitamin A are stored in fat tissue.

The low fat percentage of dogs affects the amount of stored vitamin A, so vitamin supplementation may be considered for greyhounds and other sighthounds earlier than for other breeds.

The liver releases vitamin A with the help of an enzyme containing zinc, and it is transported to its destination, such as the retina, skin, or testes, by two proteins. Therefore, a lack of zinc means vitamin A cannot be utilized, and a lack of proteins means it cannot be transported.

Vitamin A₂

Usually, when talking about vitamin A, it is used either as a general term or to refer to vitamin A₁. Fish are an exception in many ways from mammals, and one such difference is vitamin A₂. It is otherwise similar to vitamin A₁, but it has a small difference in chemical structure, an extra double bond. For this reason, its biological activity is 40-50% of vitamin A₁, or conversely, twice as much would be needed as the so-called “normal” vitamin A. However, this has little practical significance and belongs to the category of trivial knowledge. On average, less than 10% of fish liver oil is vitamin A₂¹.

Functions of Vitamin A

Vitamin A affects the growth of cells and their differentiation. Therefore, it is very important in immune response and sensory development. Vitamin A is crucial for bone development. Additionally, it participates in skin protection and prevents mucous membranes from drying out. It also plays an important role in reproduction and fertility. In the eye, vitamin A contributes to night vision and color perception.

Vitamin A is needed – in addition to vision

• for normal growth and development
• for the development of immunity
• for pregnancy, fertility, and sperm production
• for healthy skin
• affects several transport proteins and enzymes
• affects fat metabolism

Carotenoids such as beta-carotene and lycopene, found in tomatoes, also act as antioxidants.

Vitamin A Deficiency

In carnivores, including dogs, the vitamin A content of food affects the vitamin A content of the blood, and based on that, one can assess the adequacy of vitamin A intake if a deficiency is suspected (Basset et al. 1984, Wilson et al. 1987, Schweigert et al. 1990).

A deficiency in vitamin A causes fertility disorders, fetal mortality, muscle weakness, mucous membrane and skin diseases, poor coat and nail condition, and night blindness.

Because vitamin A strongly influences the development of immunity, a deficiency in vitamin A causes a higher risk of diarrhea and respiratory infections in children. It is entirely possible that the same applies to dogs, considering their rather common tendency to show symptoms through their stomachs.

A dog fed with dry food is unlikely to suffer from a severe deficiency, but in raw feeding, care must be taken to ensure that the raw materials used provide sufficient vitamin A intake. When cooking meat or other products, it must be remembered that cooking destroys some of the vitamin A. However, a severe vitamin A deficiency is very rare.

Overdose

Overdose accumulates over a longer period. Symptoms include dry skin, loss of appetite, irritation of the eye conjunctiva, bone disorders, and liver damage. However, these symptoms require significant overdosing of vitamin A. A milder overdose may be caused by a zinc deficiency, as it weakens the breakdown of vitamin A, causing it to accumulate in the body faster.

The toxic dose for dogs is not known, but in humans, a single dose 100 times the recommended amount for adults and 20 times for children can cause toxicity. Symptoms usually include nausea, headache, dizziness, impaired vision, and muscle dysfunction. Long-term, lasting from several weeks to a year, about 10 times overdose can lead to chronic vitamin A toxicity.

Dogs and foxes can excrete up to 60% of the vitamin A they receive in urine, which is apparently one reason why dogs can have very high blood vitamin A levels without easily experiencing overdose symptoms (Schweigert et al. 1991). Dogs tolerate up to 50 times the vitamin A levels without toxicity symptoms (NRC 1985, Golby et al. 1996).

Generally, with the precursors of vitamin A, carotenoids, an overdose is not achieved because the body itself regulates the production of vitamin A.

Requirement

The maintenance dose for a normal dog is 75-100 IU/kg/day. Often amounts for puppies are presented as 270 IU/kgBW and for adults 70 IU/KGBW. The maintenance range is then wider, 80 – 500 IU/BWkg. Australian veterinary and scientic Gannon recommends a daily dose of 2500 IU for a competing greyhound, which is 83 IU/kgBW/day for a calculated 30 kg dog. Instead, the book Care of the Racing Greyhound mentions 4000 – 5000 IU/day for a competing dog.

Labrador Retriever and Miniature Schnauzer puppies were given increasing doses of vitamin A from weaning to one year of age, starting at 1500 µg/4184 kJME (1000 kcalME) and ending at 30000 µg/4184 kjME (5000 – 100,000 IU). The puppies’ growth was monitored, and blood values were measured regularly during the experiment. The given amount of vitamin A did not affect growth or blood values except for increased serum retinol (Morris et al. 2012²).

A dose of 10,000 IU of vitamin A for 10-14 days is recommended for dogs with gastrointestinal disease caused by some bacteria or virus. The same dosage can also be used to assist in the formation of antibodies for vaccination if there is a threat of kennel cough or distemper.

A dose of 10,000-20,000 IU per day for 6-8 weeks is recommended for tendon and joint injuries.

Large doses of vitamin A should never be given orally without first discussing the matter with a veterinarian. Injectable vitamin A should never be given without a veterinarian’s prescription.

Vitamin A has been reasonably well studied in sled dogs. According to Golby et al. (1996), vitamin A levels in food from 2000 – 200,000 IU/kg of dry matter are safe for dogs, but over 400,000 IU of vitamin A per kilogram of dry matter endanger the dog’s body’s ability to maintain a normal balance of vitamin A, homeostasis. At the lowest vitamin A level, 2000 IU/kg of dry matter, the vitamin A level in dogs’ livers decreases. NRC’s (1985) minimum recommendation for vitamin A content in food is 3336 IU/kg of dry matter, and AAFCO’s recommendation is 5000 IU/kg of dry matter. Based on the results of this study, sled dogs have been able to use double the vitamin A levels for maintenance needs (200 IU/BWkg/day) during the training season, and triple (300 IU/BWkg/day) vitamin A levels during intense stress without adverse effects. According to Grandjean (1989), the vitamin A intake of sled dogs can be double the maintenance level.

In simplified terms, there is no risk in giving liver if there is a fear of vitamin A overdose.

Supplements

Actual vitamin A is not sold as a supplement per se for dogs (*there is variety per country, though*), but it may be found as beta-carotene. Beta-carotene can be given in courses, such as a week on and a week off. Beta-carotene is safe to give because its conversion to actual vitamin A is effectively regulated, but this is also its weakness – it cannot be used to “boost” vitamin A levels. Additionally, beta-carotene converts to vitamin A at a low ratio.

If there is a need to give a higher amount of vitamin A to a dog, it should be done, for example, with liver or by using an ADE solution. Beta-carotene supplements are intended to correct mild deficiencies and support vitamin A production for humans and horses.

Vitamin A in Feeding

When talking about vitamins, it is usually mentioned in a side note that vitamin A is needed for eye health. That is true, but it is a considerable understatement. In my classification, vitamin A is one of the three most important protective nutrients – the other two are vitamin D and zinc. Vitamin A is an important factor in cell division and differentiation and thus also in the development of immunity. Especially for pregnant females, vitamin A is a significantly important addition. However, there are warnings about vitamin A toxicity, which is why its main source, liver, is feared, and carrot shavings have been offered to dogs, seeking vitamin A through its precursor beta-carotene by providing poorly digestible raw root vegetables. Even the much-maligned ready-made liver casserole is a better source of vitamin A than carrots.

“Pure” vitamin A is only obtained from animal sources, with the most important being liver, but eggs also serve as a source of vitamin A. However, liver is problematic for some dogs, apparently due to its strong smell, and if a dog simply refuses to eat liver, the owner’s enthusiasm does not extend to frying or drying the liver, and eggs are not an option if the dog starts to gain weight, then supplements are the only option left. In practice, we are talking about cod liver oil or an ADE solution, as most canned goods are in the form of beta-carotene, i.e., a precursor of vitamin A.

The mere amount of vitamin A (or beta-carotene) given does not save anything. Since everything in the body depends on everything else and many factors go hand in hand, the same applies to vitamin A. If a dog has a zinc deficiency, and many do, vitamin A cannot be utilized. If there is a protein deficiency in the diet, one of the first “sufferers” are transport proteins – as the little that is obtained is used to build and repair more important tissues – and vitamin A cannot be transported from place A to place B. As a fat-soluble vitamin, it needs fat to function, and if there is so little fat in the food that it all goes to energy, all fat-soluble vitamins are in trouble.

The most important factor affecting vitamin A is zinc.

Now we are at the depths of the origins and move to a gray area where the cards of the owner’s belief and other assumptions are played on the table.

If you belong to the school that believes the body takes care of itself, then beta-carotene is an option because it is converted as needed – that is, the body’s basic need can be satisfied with the precursor whenever vitamin A levels drop. If, on the other hand, you believe that enough beta-carotene is never obtained from food because it is plant-based, and the “conversion ratio” to pure vitamin A is not sufficient, then beta-carotene preparations are not an option. If you are convinced that the basic need can be satisfied with food, but optimal results require boosting, then the only available option is liver.

Need and Toxicity

There is a problem with vitamin A recommendations and toxicity limits – no one actually knows the exact, or even more competent, indicative limits. It is known that reported problems due to vitamin A overdose are so rare that it could even be said that they do not exist.

Of course, certain guidelines for intake have been given.

According to AAFCO, food should contain at least 5000 IU of vitamin A per kilogram of food and a maximum of 250,000 IU. If these are converted to micrograms per hundred grams through animal-based retinol, the limits are 150 µg/100 g and 7500 µg/100 g.

These are the limits defined for dry food manufacturers for the need and the highest safe intake.

If a dog eats 400 g of dry food with that concentration, it will get a maximum of 600 µg of vitamin A per day – without considering absorption or the source of vitamin A. For comparison, Royal Canin’s Maxi Adult contains 16,000 IU/kg, or 480 µg/100g (*old data*). So it provides vitamin A over three times the basic recommendation of AAFCO, which is not a bad thing. However, it must be remembered that the primary role of vitamin A in dry foods is to act as part of preservation, so even though dogs benefit from the amount, it can be questioned whether the excess is due to the dogs’ needs or the manufacturer’s needs. Either way, calculatively RC provides 1920 µg with a 400 g serving, and we get another reference value.

NRC states in Nutrient Requirements of Dogs and Cats that since vitamin A intake has not been studied concerning liver accumulation and others, nor specifically for pregnant/lactating females and growing puppies, vitamin A should be offered through the energy content of the food at 303 µg/1000 kcal.

Regarding the toxicity limit, or the highest safe daily intake, we are in as weak a position as with intake recommendations.

NRC’s Nutrient Requirements of Dogs and Cats states:

In 1949, two two-month-old greyhound puppies were given 90,000 µg/BWkg of vitamin A (300,000 IU) for 30 days, and they developed vitamin A-induced toxicity. This might be one limit regarding overdose, at least for puppies.

In 1975, vitamin A overdose was studied in Labrador Retriever puppies. At 10 weeks (approx. 6kg), they were given

• retinol 30,000 µg/BWkg once a week for 10 weeks and then 90,000 µg/BWkg for 88 days, or
• 60,000 µg/BWkg once a week for 14 weeks, or
• in two other groups continuously 30,000 or 60,000 µg/BWkg once a week

After 11 weeks, each puppy began to show toxicity symptoms.

In 1997, adult dogs were studied for a year, giving them retinol calculated through the food’s energy at 67,500 µg/1000 kcalME per day, and no signs of vitamin A overdose were found in bone studies.

Based on a 1996 study on one-year-old beagles, it was reported that maintenance feeding can use 60,000 µg/kgDM doses without problems.

NRC’s 1987 edition does not provide a clear limit for the highest safe daily intake but recommends for dogs

• no more than 10 times the recommended daily intake
• for puppies no more than 15,000 µg/kgDM when the food has 4 kcal/g
• for adults no more than 64,000 µg/kgDM when the food has 4 kcal/g
• there are no studies on vitamin A intake for pregnant or lactating females, so the same is recommended as for puppies

Generally, without going into too much detail, the maintenance requirement for vitamin A in dogs is stated to be 75-100 IU/kgBW, which is 22.5 – 30 µg/kgBW as retinol. For a 10 kg dog, that’s 300 µg, and for a 30 kg dog, 900 µg.

Food Bowl

Dogs living on dry food practically satisfy the maintenance requirement. On the other hand, those on raw feeding must calculate and consider.

If the maintenance requirement, i.e., practically the minimum requirement, for a 30 kg dog is 900 µg, and 100 g of liver provides 20,000 µg, simple division tells that a little over 30 grams per week is enough. If we assume 80% absorption for liver vitamin A, a little more is needed. When using eggs, the same 30 kg dog’s basic vitamin A need could be satisfied with half a dozen eggs a day, which is too much as the only source. But one egg provides about 15% of the daily need for the dog.

Since vitamin A can be quickly and easily obtained with the right raw materials, the real concern is the dog’s risk of toxicity.

If the highest limit calculated through the food’s energy is accepted as 67,500 µg/1000kcalME, then if only beef with 15% fat is given, it provides about 135 kcal/100 g. Thus, about 740 grams of meat would be needed to obtain 1000 kcal. So now let’s play, just for simplicity, that we have a 25 kg dog for which that amount of meat would suffice. Then it could be given nearly 350 g of liver per day without worry. This can be compared to the maintenance recommendation of about 750 µg for that 25 kg dog.

Overdosing vitamin A to the point of toxicity is not easy.

If giving beef or pork liver is doubted for some reason, American barf guru Monica Segal states about 3290 µg/100 g for chicken liver. Finnish official nutrition database Fineli, on the other hand, states 9747 µg/100 g for chicken liver.

RAE

When investigating the vitamin A content of different raw materials, one often encounters the notation RE or RAE. This indicates the total vitamin A content of the food concerning how it would correspond to biologically active vitamin A, i.e., retinol. Finnish database states 774 µg/100 g RAE for carrots, but we know that carrots do not contain any vitamin A; it is in the form of its precursor, beta-carotene. RAE, or retinol activity equivalent, indicates what amount of vitamin A it would correspond to if converted. Previously, RE, or retinol equivalent, was used, and it is still used in foreign databases and older articles. It is essentially the same thing, but the conversion ratio used is different.

The equivalent ratio thus describes the relationship between retinol, beta-carotene, and other carotenoids acting as precursors of vitamin A, and they have been converted into vitamin A in micrograms

• in retinol activity equivalent (RAE) the ratio is 1: 12 : 24
• in retinol equivalent the ratio is 1 : 6 : 12

In beta-carotene, 12 µg and in other carotenoids, 24 µg corresponds in activity to one microgram of vitamin A. When there are over 11,000 µg/100 g of carotenoids in carrots, it corresponds to only 774 micrograms as vitamin A, meaning if one wanted the same amount of active vitamin A from carrots as from beef liver (19,600 µg/100 g), it would mean eating 2.5 kilos of carrots.

Vitamin A and Energy

Vitamin A is an important factor in cell division and differentiation. Thus, it also has a significant role in normal growth and development. If a vitamin A deficiency is caused, growth retardation is no longer of any significance, as staying alive in general health becomes the most acute problem.

In rodents, vitamin A reduces body fat by affecting energy production. However, no one knew whether vitamin A could affect the body composition, structure, and growth of dogs. This is essential information not only for puppy feeding but also to know if rat experiments could be applied to dogs. Therefore, the matter was studied. Vitamin A was given to 24 Labrador Retriever puppies from eight weeks of age to 78 weeks (1.5 years) and 25 Miniature Schnauzer puppies to 52 weeks (Brenten et al. 2014³). The amount of vitamin A was increased with age from 1500 µg/4184 kJME (1000 kcalME) to 30,000 µg/4184 kJME. The feeding of growing puppies was monitored and compared to the estimated energy requirement. Growth curves were made for the puppies, and growth and obesity were assessed weekly, according to which feeding was adjusted as needed. Body composition was examined at weeks 26, 52, and for Labrador Retrievers at the end of the study at 1.5 years of age with X-rays. The results were not surprising to those familiar with practical life, but now research data was obtained as a basis.

The growth of the puppies followed the growth curves of their breed, meaning vitamin A did not affect growth. Nor did vitamin A have an effect on body composition or obesity. However, it was observed that there were the largest variations in energy use throughout the growth period both between puppies and breeds. Although a nice growth curve is obtained over a longer period, actual growth and the energy required for it vary, and puppies grow differently.

The study did not tell anything about affecting growth with nutrition, and in fact, it tried to find out if vitamin A affects obesity.

Pregnant and Nursing Females

In the late 80s in Finland, mothers were scared, so to speak, into loose pants about the dangers of vitamin A. Liver was declared completely outlawed for pregnant women, and the entire nation received its share. Liver sausage was given almost for free, and ready-made liver casseroles were available for a dime – for the euro generation: for less than 20 cents. We had a freezer full of liver casserole, and the fridge was bursting with liver sausage and pâtés. The dogs also got their share when we could no longer stand to even see such food.

Of course, there are risks in excessive vitamin A intake. But it is known that for normal people (of course, pregnancy is also a normal state), 100 times the recommended doses start to be problematic. In long-term excessive intake, ten times might cause toxicity. According to Fineli, a normal 400-gram liver casserole contains about eight milligrams of vitamin A, but liver itself has much more – one hundred grams of beef or pork liver contains about 20 mg of retinol, which theoretically covers a month’s need.

Of the forms of vitamin A, retinoic acid is the actual risk. When an animal receives some vitamin A derivative, it is first converted into retinal and then into retinoic acid. Retinal is used in the eyes, but that does not interest us now. Instead, the derivative, retinoic acid, is more interesting because it regulates a little learning, memory, reproductive ability, skin construction, bone shaping, and the immune system – all those things for which vitamin A intake is a concern. During pregnancy, retinoic acid regulates hundreds of genes, some of which affect fetal development. And now we have reached the point. It forms compounds called teratogens, which are harmful to the fetus in the early stages of pregnancy. In the worst case, they can cause developmental disorders. Synthetic vitamin A preparations pose a greater risk than liver, as the risk arises at lower amounts. The limit has been considered that if a mother receives no more than 800 µg/day of vitamin A in the early stages of pregnancy, i.e., about four grams of liver, there is no risk. Even that has a considerable safety margin.

There are two things to consider here. The first is that in humans, the early stage of pregnancy, for example, the first trimester, is equivalent to the time from mating to weaning in dogs. For a puppy, the corresponding development period is about 2 – 4 weeks, depending on the calculation method. The second is that there is no indication that the same applies to dogs at all. Dogs still regulate their vitamin A levels because they are predators and have learned to tolerate liver and higher vitamin A levels during their evolutionary history. If human risks, which are remarkably low here, and liver restrictions were implemented because humans should have zero tolerance, are directly transferred to dogs and thus deprive a pregnant female of an absolutely important, even vital, vitamin for her and her fetuses, then it is more than going from the frying pan into the fire. It is going straight into the swamp.

By the way, where does anyone find synthetic vitamin A? They are practically either plant-based derivatives, calling which vitamin A borders on deception, or based on cod liver oil, in which case they are not synthetic. Synthetic vitamin A is encountered as a food additive.

Public health, however, reacted in part in the 80s. At that time, a lot of vitamin A supplements were given on the livestock side to improve fertility and general vitality (livestock benefited only; it is worth remembering in the case of females and puppies), and because vitamin A accumulates in the liver, intakes exceeded previous estimates. Overdoing occurred on two fronts. First, known fetal damage caused by vitamin A overdose resulted from strong supplements, not known from food. Likewise, the public reaction that labeled everything liver as biohazard was at least headline-seeking. The problem, or rather the potential problem, no longer exists, as unwarranted A-boosting has been stopped on the livestock side. Dogs tolerate much more vitamin A than humans, and although it is fat-soluble, they can also excrete the excess.

According to NRC recommendations, the need for vitamin A in dogs is 105 μg/kgME/day for puppies and 50 μg/kgME/day for adults. The safe intake limits would be 1044 μg/kgME/day and 2099 μg/kgME/day, respectively. This means that no dry food reaches any risk limits, but each meets the intake recommendations. Healthy dogs fed with dry food never have a vitamin A deficiency. At least in principle. The tuning of dry foods is increasing all the time, and if, for example, a 30 kg dog is given 400 g of dry food containing 10,000 IU/kg of vitamin A and 100 g of liver is added, the dog already receives significantly more vitamin A – 20,000 μg⁴. Even then, it does not reach anywhere near the toxicity limit, but the safe intake limits are almost reached. But even if given in excess, or using better vitamin A-fortified 20,000 IU/kg food, there is no reason to lose sleep. This does not take into account the dog’s ability to excrete vitamin A. And hardly anyone gives over 100 grams of liver to their dog every day – in addition to dry food.

One thing to remember is that to utilize vitamin A, fat is also needed. Carrot beta-carotene does not comfort a barfer much if there is no fat at all.

Vitamin A deficiency in dogs is not present in principle anywhere other than in laboratory conditions. Intake amounts are sufficient with normal feeding. The problem becomes what each person understands by normal. If a dog lives in a stressful environment and under strain, vitamin A consumption increases. If the owner’s concept of normal feeding is bone, cartilage, chicken wings, and necks, and frozen cucumber, lettuce, and zucchini puree, then the lack of vitamin A begins to be a reality. There have been doubts about the bioactivity of vitamin A supplements and the naturalness of the sources in dry foods. The general belief is that synthetic vitamins do not work as they should, but the body treats them in places like foreign substances, reducing their bioactivity significantly. The matter is being studied, for example, regarding folic acid around the world. Similarly, there is a question mark about how fat intake and quality affect vitamin A. In both, there is often room for improvement in dog feeding.

We have all been taught that carrots must be eaten to see in the dark. Night vision is indeed one thing that vitamin A is related to. But it functions in many other ways as well. It plays an essential role in regulating cell membrane function, bone and tooth growth, immune response, reproductive hormone production, skin and mucous membrane cell construction, and protein synthesis. Additionally, vitamin A (and beta-carotene) is an antioxidant. Has the attention of sports dog owners been awakened? How about mentioning things like skin problems, poorly functioning digestion and intestines, allergies, and other immune disorders, or bone development disorders? However, we know that dogs have sufficient vitamin A intake, so these problems cannot be related to inadequate vitamin A intake or poor utilization – or can they? I don’t know, but including liver, fish, and fish oils in the diet might not be a bad idea.

When talking about reproduction, vitamin E is always brought up. Not without reason, as a vitamin E deficiency can be a real threat, especially as raw feeding increases – fat always requires vitamin E as a companion. Dry food feeders are not safe either, as the vitamin E content of food bags decreases over time and with external factors, and the synthetic antioxidants used in preservation do not have the same “effect” in the body, even though the food’s fat remains preserved without rancidity. But vitamin A should not be forgotten either. It plays a very essential role in fertility, sperm, and embryo development.

Did I already mention adding liver and fish to the diet?

Also, check out Clagett-Damen and Knutson’s review on the subject: Vitamin A in Reproduction and Development — you should find it from PubMed.

Supportive Therapy

Vitamin A is often used as supportive therapy in various diseases. Humans are familiar with the sebaceous gland inflammation known as seborrheic dermatitis. A similar skin inflammation is found in dogs, practically talking about sebaceous gland inflammation. It is often treated simply with washing, and sometimes an allergy diagnosis is made because of it, but vitamin A might also help. It is a rare but increasing disease. The cause is unknown, and there may be several that only cause similar symptoms. One reason might be as simple as a vitamin A deficiency resulting from fat deficiency. This might explain why cases resembling sebaceous gland inflammation are concentrated in dogs fed with dry food – or it could be just a coincidence due to the prevalence of dry food.

Three symptomatic dogs were given only vitamin A, and they recovered as the skin symptoms improved. Seven other dogs, which lacked the skin and hair follicle hardening related to vitamin A deficiency that the aforementioned three also had, did not benefit from vitamin A (Ihrke and Goldschmidt 1983⁵). Vitamin A itself is not a miracle cure for skin inflammations, but if a dog is on a low-fat diet and if vitamin A intake is largely based on beta-carotenes, then a simple deficiency must also be considered.

1. Lee Russell McDowell: Vitamins in Animal and Human Nutrition p. 18[↩]
2. Morris PJ, Salt C, Raila J, Brenten T, Kohn B, Schweigert FJ, Zentek J.: Safety evaluation of vitamin A in growing dogs. Br J Nutr. 2012 Nov 28;108(10):1800-9. doi: 10.1017/S0007114512000128.[↩]
3. Brenten T, Morris PJ, Salt C, Raila J, Kohn B, Brunnberg L, Schweigert FJ, Zentek J: Energy intake, growth rate and body composition of young Labrador Retrievers and Miniature Schnauzers fed different dietary levels of vitamin A. Br J Nutr. 2014 Mar 25:1-8. PMID: 24666690[↩]
4. Helleman & Marjeta: Dog Feeding pp. 110-111[↩]
5. Ihrke PJ, Goldschmidt MH. Vitamin A-responsive dermatosis in the dog. J Am Vet Med Assoc. 1983 Apr 1;182(7):687-90.[↩]