Fish, as part of a balanced diet, offers a variety of health benefits for humans. And this is equally true for dogs. Since tuna is one of the most popular types of fish, the question arises whether dogs can also enjoy it.
Adult dogs can eat tiny amounts of tuna without hesitation. However, since tuna contains mercury, dogs should only be given it occasionally. Puppies and pregnant bitches should not eat tuna at all. In addition, dogs should not eat raw tuna or seasoned tuna.
Tuna and other large, long-lived fish species contain mercury, which they absorb naturally through the food chain and accumulate in the body. Therefore, they are not the best choice for dogs.
However, a little tuna given to your dog as a treat every now and then won’t do any harm as long as it’s a healthy adult dog.
In this article, we’ll first discuss why tuna contains mercury in the first place and how you can recognize mercury poisoning in your dog.
Next, you’ll learn what types of tuna you can give your dog and what to watch out for, especially in pregnant bitches and puppies.
Finally, we’ll explain what fish your dog can eat without hesitation.
Can Dogs Eat Tuna?
There is no clear, unambiguous answer to this question. You can safely feed tuna to adult dogs, but only in tiny quantities and as an occasional treat.
Tuna should not be a regular part of your dog’s diet. It is crucial that you do not feed tuna to pregnant bitches or young puppies.
The reason for these restrictions is that it contains mercury. Excessive consumption of tuna will cause mercury to accumulate in your dog’s body, which can lead to mercury poisoning.
The same problem exists for other long-lived fish or fish high in the food chain, such as marlin, swordfish, or shark.
Why Does Fish Contain Mercury?
Mercury is a naturally occurring chemical element that some may remember from old thermometers.
It occurs in several forms, and one particularly problematic form is a compound called methylmercury.
Methylmercury is formed by certain microscopic organisms living in waterways such as lakes, rivers, and the sea. It is found where there are sources of nutrients for living things in the water.
Methylmercury does not readily disappear from a living thing’s body once ingested. Therefore, a process called biomagnification occurs in the aquatic food chain.
While bacteria in the water contain little mercury, the plankton that eat these bacteria take up more mercury.
The creatures that eat the plankton, in turn, absorb more mercury, and so on, until you get to the large predatory fish. These take up large amounts of mercury over time.
In general, piscivorous fish have higher mercury levels in their tissues than those that feed primarily on insects and plants.
Mercury levels are highest in long-lived predatory marine animals like tuna, swordfish, and sharks.
Why is Mercury a Problem?
Mercury is a big problem because it is toxic to the body. This problem affects dogs and humans alike. And even cats who like tuna are not protected from it.
Since the body cannot excrete mercury effectively, it accumulates in our tissues over time. And the more mercury that is ingested, the higher the concentration in the body becomes.
Because dogs are generally much smaller and lighter than humans, they can only tolerate smaller amounts of mercury.
Mercury accumulates in tissues and leads to problems like tissue degeneration, with the brain, kidneys, and muscles most at risk.
How to Recognize Mercury Poisoning in Dogs
Mercury poisoning is extremely rare in dogs. However, when a dog has mercury poisoning, the following symptoms may occur:
- Sudden blindness
- Agitation
- Abnormal behavior
- Abnormal chewing
- Decreased coordination
- Seizures
- Altered kidney function, manifested by more frequent drinking and urination and decreased urine production
- Hair loss
- Skin changes
Signs of mercury poisoning usually do not appear until several weeks after the poisoning.
However, these symptoms are not unique to mercury poisoning but can also occur with many other illnesses.
If your dog shows any of these signs or you are concerned that he has been poisoned, you should contact your veterinarian immediately. Your vet can then run tests to determine the cause of the problem.
What Types of Tuna Are Dogs Allowed to Eat?
If, after this questionable information, you still decide to give your dog a small amount of tuna as a treat, the question is, what kind of tuna?
There are several types of tuna. Red or bluefin tuna has the highest mercury levels and should be avoided altogether.
However, depending on the type of preservation, there may be other health concerns for your dog besides mercury content.
Tuna in Brine
It would be best not to feed canned tuna with brine to dogs or cats. This is because of the high salt content, which can harm your dog.
Tuna in Spring Water
The variety preserved in spring water is your dog’s best choice of canned tuna. This variety usually contains no added flavorings or oils that could spoil your dog’s stomach or cause other problems.
However, always check the label before buying to ensure the canned variety does not contain added salt. Some manufacturers add salt to enhance the flavor. If so, the canned food is not suitable for your dog.
Tuna in Oil
A small amount of sunflower oil should not harm your dog and may even be good for his coat. But unnecessary extra fats in the diet lead to increased calorie intake and can cause stomach upset.
For this reason, it’s best to avoid tuna in oil. Also, some of these products contain extra salt that can harm your dog.
Tuna With Herbs, Spices Or Sauces
Herbs and spices can add tremendous value to food for our human palates. But many foods we can safely enjoy are unsuitable for dogs.
For this reason, you should always prepare the tuna you feed your dog plain, without salt, pepper, or any other seasoning.
Tuna Steak
Some tuna species contain higher levels of mercury than others. Tuna steaks are often the bluefin tuna with the highest mercury content. You should generally avoid this one for your dog.
Tuna steaks from other species usually contain lower levels of mercury. So, if you can understand what type of tuna it is, you can strike at other species.
Any tuna steak should be thoroughly cooked to avoid the risk of parasite transmission.
Giving your dog a whole tuna steak is not advisable, but a small portion of a plain, unseasoned tuna steak as a treat on special occasions should be safe.
Raw tuna
You should never feed tuna or any other fish raw to your dog. Raw fish can contain parasites that can lead to serious illness.
This is also the reason why sushi is unsuitable for dogs.
How Much Tuna Can a Dog Eat?
There are no scientific studies on this question. Therefore, no guidelines exist on how much tuna dogs can eat.
Limiting the amount of tuna your dog eats to an occasional treat is best, and then only feed a small amount. We’re talking more like a small spoonful, not an entire can.
The actual amount your dog can tolerate will, of course, depend on his body size. Smaller dogs should get less tuna and not as often as larger dogs.
But no matter your dog’s size, you should not give him a whole can of tuna at once. And no dog should be fed tuna every day.
If you have given your dog tuna, you should wait a few weeks before feeding it again. And if you’re unsure, it’s best to avoid tuna altogether.
Instead, look for fish-based, dog-friendly treats, or ask your vet for dietary recommendations.
If you also feed your dog other mercury-containing fish, don’t give him tuna in addition, as this will lead to higher mercury levels.
Can Pregnant Bitches Eat Tuna?
It is not advisable to give tuna to a pregnant bitch. The reason is that mercury can pass through the placenta and thus accumulate in the fetus.
This can lead to developmental problems in the growing puppies, especially in the brain and nervous system.
Can Puppies Eat Tuna?
It is not recommended to give tuna to a growing puppy. Tuna is generally only suitable for adult dogs.
In puppies, there is a risk that mercury will affect neurological development. The nervous system of young animals is particularly susceptible to mercury exposure.
What Types of Fish Can Dogs Consume?
The best types of fish for your dog are those that have a short life span.
Long-lived species like tuna and swordfish accumulate higher levels of mercury over time.
Feeding short-lived fish reduces the risk of mercury accumulating in your dog’s body. Some examples of such fish include salmon, whitefish, tilapia, and pollock.
If you feed your dog fish, ensure you cook it thoroughly. Raw fish might contain parasites that can make your dog sick. Also, it could contain harmful bacteria like listeria and salmonella.
These bacteria can also make your dog sick. They could even lead to health problems for you and your family. Pregnant women, young children, and immunocompromised people are most at risk.
You should generally only prepare fish for your dog plain, as cooking it with oil or seasoning it with salt, pepper, herbs, or other spices can cause health problems for your dog.
This is especially true if you use garlic, which is toxic to dogs.
Make sure to remove all fishbones, even the small ones, before feeding the fish to your dog, as fishbones can be dangerous and lead to an expensive emergency room visit for your dog.
Summary: Can Dogs Eat Tuna?
Giving your adult dog a small amount of tuna occasionally is not a problem. The best option is probably canned tuna preserved in spring water.
However, tuna should never be a central part of your dog’s diet but should only be given as an occasional treat. Pregnant bitches and puppies should generally not be given tuna.
Mercury poisoning is very rare, but since it is unknown what amounts of mercury-containing fish are still safe for dogs, caution should be exercised.
If your dog shows signs of poisoning, contact your veterinarian immediately.
