With his imposing size, sleek coat, and distinctive black-masked face, the Mastiff, also known as the English Mastiff and Old English Mastiff, is probably not the dog you think he is. Certainly he's the largest of the dog breeds -- not the tallest, but the heaviest, routinely weighing in at more than 200 pounds. One holds the record for the heaviest dog of all time, a 343-pound bruiser named Zorba.

Traits, Personality and Behavior

If you're physically up to the challenge of an extremely powerful dog who probably outweighs you, who is gentle and loving but has a definite stubborn streak (and that's not a euphemism for aggression; the Mastiff is typically more selectively deaf than defiant), and don't mind a certain amount of slobber, then the Mastiff may be right for you.

If you want to leave him tied up in the backyard to protect your home, or view him as a status symbol because of his size or image, then he's definitely not the dog for you. A Mastiff's protective nature won't assert itself on behalf of an arbitrary property line nor in defense of a few bricks and boards; it's his family he protects, and that means you need to make him part of yours. Leave him in the yard all the time, and all you'll get are some spectacular holes in the lawn and a bored, lonely, sad and destructive dog whose potential is being completely ignored.

When it comes to everyday considerations, the Mastiff is easy to live with. He'll certainly alert you if someone comes to the door, but he's mostly a quiet presence in the home. His short coat sheds, but brushing a couple of times a week will help keep it under control. And while he does slobber, he's not a world-class slobberer, and it can mostly be handled with a quick wipe after he's eaten or had a drink of water. Still, if you're totally against dog slobber, don't get a Mastiff.

Obedience training needs to be consistent and fair, and must begin when your dog is a puppy, before bad habits have a chance to take hold. In particular you need to teach your Mastiff not to pull on the leash or jump on people, or he'll be a hazard to anyone he's around when he's full-grown.

The key to developing proper Mastiff temperament as an adult is to socialize him around all kinds of people when he's young. Far from making him less protective, it will make him more effective as a protector. He'll know all the "right" body language that tells him someone is a friend. He'll be familiar with how children, the elderly, kids on bikes and skateboarders look, move, and sound, and he'll use that information to pick out those with bad intentions all the more readily.

Speaking of children, Mastiffs usually love them and treat them with instinctive care, but the reality of a dog this big is that he can unwittingly hurt or scare a child. Be cautious and always supervise dogs and kids when they're together. If you have toddlers, consider waiting until they're older to bring a Mastiff into your family.

Health Issues Common to Mastiffs

As might be predicted, given their large size, Mastiffs suffer from a number of joint and structural problems. It's important that young, growing mastiffs be kept lean and not allowed to exercise too strenuously or eat too much, as this will lead to injuries and problems that can be crippling down the road. In fact, all Mastiffs need to be kept lean, as obesity increases the chances they'll develop structural problems and makes them more painful when they occur.

The Mastiff can be affected by a very long list of eye diseases, so having your dog's eyes examined annually by a board-certified veterinary ophthalmologist is essential.

Musculoskeletal Conditions

One such structural problem is the genetic hip deformity known as hip dysplasia. The head of the thigh bone doesn't fit properly into the hip socket, and over time the bone begins to wear away. The constant inflammation leads to arthritis. It's treated with surgery, usually total hip replacement. Untreated, the dog will suffer pain and lameness. Elbow dysplasia is a similar condition affecting the elbow.

It's impossible to know if a dog has hip or elbow dysplasia simply from examining him or watching him move. Nor can hip and elbow dysplasia be ruled out entirely just because the parents were free of the condition, although it reduces the risk. And a puppy's hips and elbows can't be evaluated; only at the age of two you can know if a dog is or isn't affected.

Neurologic Conditions

Another breed-related structural problem affecting the Mastiff is cervical vertebral instability (CVI), commonly called Wobbler's syndrome. It's caused by a malformation of the vertebrae within the neck that results in pressure on the spinal cord and leads to weakness and lack of coordination in the hindquarters and sometimes to complete paralysis. Symptoms can be managed to a certain extent in dogs who are not severely affected, and some dogs experience some relief from surgery, but the outcome is far from certain. While CVI is thought to be genetic, there is no screening test for the condition.

Cardiovascular Conditions

Their large size also puts quite a strain on the Mastiff's heart. He's at risk for a number of conditions, including cardiomyopathy, which causes an enlarged heart. An annual heart exam is critical in catching these conditions as early, and no dog with cardiomyopathy should ever be bred, nor should any Mastiff be bred without a comprehensive heart examination by a board-certified veterinary cardiologist and OFA certification in the previous year. The sad reality, however, is that a dog who tests fine one day can develop heart disease the next, and the puppy of two parents without heart disease can still develop it.

Gastrointestinal Conditions

Mastiffs are also more likely than many breeds to bloat, a condition in which the stomach twists on itself, cutting off blood flow. Bloat strikes very suddenly, and a dog who was fine one minute can be dead a few hours later. Watch for symptoms like restlessness and pacing, drooling, pale gums and lip licking, trying to throw up but without bringing anything up, and signs of pain. Bloat requires immediate veterinary surgery, and most dogs who have bloated once will bloat again. That means it's wise to opt for the procedure known as "stomach tacking," which will keep the stomach from twisting in the future. This procedure can also be done as a preventive measure.

Urinary Conditions

Cystinuria is a genetic kidney defect that leads to the formation of bladder stones that are very difficult to manage with diet or medication and often requires surgery both to remove the stones from the bladder and to repair urinary blockages. There may be no advance signs that the dog is forming cystine stones, and many veterinarians are unfamiliar with cystinuria and may mistake them for more common stones such as struvites. Urinary blockage is a life-threatening veterinary emergency.

Unfortunately, the current screening test for cystinuria is of limited use, as it frequently gives a false negative. It does not give false positives unless the dog is on a particular type of antibiotic at the time the urine sample is taken, however, so a dog who tests positive does, in fact, have the condition, even if he tested negative in the past or tests negative in the future. There is no genetic screening test, so it's impossible to determine if a dog is a carrier or not.

To protect yourself from the expensive vet bills associated with these conditions, you'll want to purchase pet insurance for your Mastiff before they show symptoms or are diagnosed.

Condition Risk Profile Cost to Diagnose and Treat
Hip Dysplasia Medium $1,500-$6,000
Elbow Dysplasia High $1,500-$4,000
Entropion High $300-$1,500
Cardiomyopathy High $500-$1,500
Gastric Dilatation Volvulus (Bloat) High $1,500-$7,000
Pulmonic Stenosis High $1,000-$7,000
Panosteitis High $200-$800

8 Tips to Bring Home a Healthy Mastiff Puppy

Don't ever, ever, ever buy a puppy from a pet store or Internet site that offers many breeds and popular mixes, or that ships with no questioned asked. If you buy a puppy from these sources, you'll be more likely to get an unhealthy, unsocialized and difficult to house-train puppy and will be supporting the cruelty of high-volume puppy mills.

Start your search for a good breeder at the website of the Mastiff Club of America, and locate a breeder who has agreed to abide by its Code of Ethics.

Ask your breeder to show you the results of genetic health testing. All breeders should be able to show written documentation from the Orthopedic Foundation for Animals (OFA) and the Canine Eye Registration Foundation (CERF) clearing your puppy's parents of hip and elbow dysplasia, heart disease, and eye problems. PennHip certification of hips is also accepted. Ideally they will also have OFA certification of thyroid health, and the results of at least one normal urine test for cystinuria, done by the University of Pennsylvania.

Pay close attention to your potential puppy's temperament. While most Mastiffs do have good temperaments, because of their size, a breeder who has American Temperament Test Society (TT) certification on her dogs is to be preferred over one who does not.

Don't fall for the lies of a bad breeder. As is true with any breed who is the "most" of something -- smallest, tallest, cutest -- the Mastiff is sometimes the target of puppy millers and unethical breeders. These sources will have a thousand excuses -- such as that they don't need to do those tests because they've never had problems in their lines, or because their dogs have been "vet checked" -- as to why they haven't done the health and temperament testing that good breeders do, but that's all they are: excuses. The minute you hear something like that, walk away.

Consider an adult dog from a shelter or a rescue group. Because many young Mastiffs are a handful, and many healthy defects hide until maturity, you can avoid both problems by adopting an adult Mastiff (or mix) from a rescue group or shelter.

Puppy or adult, take your Mastiff to your veterinarian soon after adoption. Your veterinarian will be able to spot visible problems, and will work with you to set up a preventive regimen that will help you avoid many health issues. Ask specifically about what to do it if you suspect your dog is bloating, and how best to monitor your dog for other potential health risks.

Make sure you have a good contract with the seller, shelter or rescue group that spells out responsibilities on both sides. In states with "puppy lemon laws," be sure you and the person you get the dog from both understand your rights and recourses.

Pet Insurance for Mastiffs

Pet insurance for Mastiffs costs more than for mixed breed dogs. This is because Mastiffs are more likely than mixed breed dogs to make claims for hereditary conditions that are expensive to treat.

Embrace dog insurance plans offer full coverage for all breed-specific conditions (excluding those that are pre-existing) to which Mastiffs are susceptible. The best time to get pet insurance for your Mastiff is when he's a healthy puppy. You can't predict what will happen in the future, and pet insurance is the one thing you can't get when you need it the most.