Linda Simon
Dr Linda Simon (MVB MRCVS, University College Dublin)
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A formidable dog that has more brawn than brains, the Masti-Bull is a mix of the large English Mastiff and the resilient American Bulldog. They are a moderately active breed that can be a handful and require an experienced trainer to unleash their full potential and prevent any vices or aggressive tendencies from developing.

Bulky and beefy are two words that spring to mind when one sees a Masti-Bull. They are heavily muscled with a large skull and strong, lean limbs. They have a short, straight coat, which can be a multitude of colours, including brindle, fawn, grey and white. With their solemn brown eyes and loose-hanging facial skin, they often have a sad and serious expression.

About & History

We don’t know a great deal about when the first American Bulldogs and English Mastiffs were crossed together, though it likely occurred sometime in the last couple of decades. However, each parent breed has several centuries of history to its name, so we can take a closer look at them to try and learn more about the recently-developed Masti-Bull.

The American Bulldog

The American Bulldog is not to be confused with the English Bulldog, an entirely different breed that is far smaller. American Bulldogs were developed during the 1600s in the Southern United States and were admired for their strength, grit and determination.

They were employed in a number of roles, including as guard dogs, cattle herders and hunting dogs. Interestingly, they were particularly valued for their ability to keep down the wild hog numbers as hogs were a notable pest of the time. It should be noted that during the 1900s it became necessary to cross the American Bulldog to the more popular English Bulldog as breed numbers had dwindled so low.

The English Mastiff

English Mastiffs are best known for their imposing size, with some individuals reaching weights of above 100kg! This breed descends from ancient Molosser dogs who would roam the mountains in Central Asia, keeping predator numbers low and protecting the local livestock. Over the years, the dogs were bred for various purposes and would have been traded internationally. Sadly, bull baiting and dog fighting feature heavily in their history as these activities were seen as ‘sport’ in the past.

Thankfully, the outlawing of such barbaric pursuits has meant that the English Mastiff no longer has to participate. However, the banning of blood sports meant that the English Mastiff’s breed numbers dropped dramatically and it was necessary for the Bullmastiff to be bred in, in order to prevent their complete extinction.


The Masti-Bull is a large dog with a sizeable head and sturdy body. Their forehead is flattened and covered in vaguely wrinkled skin. Their eyes are well spaced and brown in colour. They have floppy ears that sit snugly to their skull. While some owners may crop the ears, this is a procedure that is seen as unethical and is banned in many countries today. Their upper lip is droopy while their jaw is big and powerful. They have a thick neck that is well wrinkled and leads to a deep chest. Their robust body is barrel shaped and they have a long and slender tail.

A fully-grown Masti-Bull will weigh between 45kg and 65kg and it is common for the males to weigh significantly more than the females. When measured to the withers, they stand at 71cm to 82cm tall. The short, low-maintenance fur of the Masti-Bull is fine and soft to the touch. Dogs can be brown, white, fawn, black, brindle and white. Often, dogs will have a dark black muzzle and patches of white on their coat.

Character & Temperament

The Masti-Bull is a dog that is commonly misunderstood, with most assuming that they are short-tempered and aggressive. In fact, the Masti-Bull could be described as a gentle giant and would rather walk away from confrontation than get involved. However, they can potentially become aggressive in the wrong hands and some owners may abuse this trait, which gives this cross-breed a bad name.

Some individuals are sensitive and will rely heavily on their owners for reassurance and guidance. If not dealt with, this anxiety can lead to hostility towards strangers so it is essential that they are thoroughly socialised when younger. Most are sociable and form strong attachments with the children in the household, acting as a sort of nanny figure.

While big and strong, the Masti-Bull is not especially athletic and can, in fact, be quite lazy. Once their exercise needs are met, they can usually be found sleeping flat out inside the home and may prove difficult to wake up at times!


All Masti-Bulls must be trained to a high degree to ensure they develop into well-rounded, calm adults. Not training them sufficiently can result in a dog that is wary around new people and is difficult to bring to places, such as the groomer and vet. As these dogs can be sensitive, it is best to use only positive reinforcement training and to encourage good behaviour with lots of treats and kind words.

Many Masti-Bulls have a strong prey drive, which can be difficult to train out of them. This means that working on their recall is especially important as they can become distracted by the smells of different animals when outdoors.


Masti-Bulls are so large that their size can affect their health. As with other giant breeds, there are certain medical conditions that we see more often in them than in their smaller counterparts. Most will live around 8 to 11 years, which is relatively short for their species.

Hip Dysplasia

Hip dysplasia tends to be a condition that is managed into old age rather than cured. Dogs who are affected will benefit from being kept lean and trim as any excess weight will put additional pressure on their joints.

Using heated, orthopaedic beds can help them cope, particularly in the winter. On top of this, most will require long-term pain relief and anti-inflammatory medicine. Adjunctive therapies, such as acupuncture and massage, can prove beneficial for many.


Oftentimes a diagnosis of hypothyroidism is delayed as owners mistake the signs for their dog simply ‘getting older’. Affected pets may become slow and sluggish and can develop repeated skin infections.

If a diagnosis of hypothyroidism is suspected, vets will measure the T4 level, which will be low. However, other illnesses can cause a reduced T4 level, so further tests are typically required to get a definitive diagnosis.


Bloat is a condition that occurs when air and liquid fill the stomach and are unable to be released. Not surprisingly, this causes a great deal of discomfort and dogs become quickly distressed.

They will walk around and retch in an effort to release the pressure. Their abdomen will quickly become bloated and the internal pressure can result in shock and organ failure. Immediate veterinary attention is required to relieve the bloating and failure to seek treatment can result in death.

Cherry Eye

All dogs have a third eyelid called the nictitating membrane that can prolapse in some causing a condition colloquially known as ‘cherry eye’. It is best to address this issue as a cherry eye can lead to chronic infections down the line.

While in the past the tissue would have been trimmed away, this is no longer advised as we know it can cause ‘dry eye’ down the line. Instead, the gland should be sutured back into place while the dog is under anaesthetic.

Allergic Skin Disease

Dogs that develop itchy skin between the ages of six months and six years and who do not have parasites are commonly diagnosed with allergic skin disease. There are a wide range of things that a dog may react to, including pollens and moulds, so determining what is causing their itchiness is important.

Exercise and Activity Levels

This big bruiser requires about an hour of structured exercise each day, which may consist of a hike over hills or a run about in the local park. On top of this, they love to participate in games, such as Frisbee and fetch. Owners can help to keep their mind active by introducing scenting games like ‘find the treat’ in the back garden.


These dogs have a coat that will not matt and does not attract a lot of dirt. Due to this, once weekly brushing is sufficient. Their ears should be checked on a regular basis as they may develop build-ups of wax.

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