Bullmastiff nutrition: lean weight, bloat, hips and lymphoma

A Bullmastiff is a heavy dog with a short life expectancy, and feeding it well mostly means keeping that weight lean from puppyhood onward. The American Kennel Club breed profile gives males as 110 to 130 pounds (about 50 to 59 kg) and females as 100 to 120 pounds (45 to 54 kg), with a life expectancy of 7 to 9 years. The AKC notes that responsible breeders screen for heart problems, hip and elbow dysplasia, hypothyroidism and eye disease, and that owners should know the signs of bloat. Cancer, especially lymphoma, is the other main concern in the breed.

Calories for a heavy, moderately active dog

Bullmastiffs vary in temperament. The AKC describes some as fairly sedentary and others as naturally active, and recommends moderate exercise, with brisk walks and play rather than running. That makes calorie needs lower than the dog's size suggests, and overfeeding easy. The Merck Veterinary Manual gives the standard starting point: resting energy requirement (RER) is 70 times body weight in kilograms raised to the power 0.75, multiplied by about 1.8 for an intact adult, 1.6 for a neutered adult and 1.4 for a dog that gains weight easily.

Figures are rounded to the nearest 5 kcal. Use the dog's lean weight, not its current weight, if it is already heavy. After neutering, drop to the neutered column and recheck weight a month later; weight often creeps up after the operation. Merck is explicit that these numbers are a starting point to adjust by how the dog responds.

Puppies

The AKC's breed nutrition note says Bullmastiff puppies grow very rapidly, which can tax their systems, and that they should be kept lean. It says most breeders advise an adult food or a large-breed puppy food for puppies to keep growth slow and steady, several small meals a day for puppies, and two meals a day for adults. Merck gives puppy needs as 3 times RER before four months and 2 times RER after, but weigh the puppy every two weeks and feed to body condition rather than to a target size. Do not add calcium to a complete puppy food. The AKC also warns against over-exercising puppies during periods of rapid growth.

Cancer, and lymphoma in particular

Lymphoma is the cancer most clearly linked to the breed. In a UK study of more than 130,000 insured dogs, the Bullmastiff was one of three breeds with a high incidence of lymphoma, alongside the Boxer and the Bulldog. It also tends to appear young. A genetic study of Bullmastiffs found an average age at diagnosis of under 6 years, and identified regions of the genome associated with the risk, which points to an inherited component.

No food, supplement or preservative-free diet has been shown to prevent lymphoma or other cancers in dogs, and that includes antioxidant-rich foods and vegetable toppers. What owners can do is notice early. The most common first sign of multicentric lymphoma is firm, painless swelling of the lymph nodes: under the jaw, in front of the shoulders and behind the knees. Feel these spots when grooming. Enlarged nodes, a new lump anywhere, unexplained weight loss or reduced appetite should go to a vet promptly.

If a Bullmastiff is diagnosed with cancer, the diet becomes part of treatment and should be planned with the oncology team. Supplements, including high-dose antioxidants and fish oil, should not be started without asking, since some can interact with chemotherapy.

Bloat

Gastric dilatation-volvulus (GDV) is a stomach that fills with gas and twists on itself. It is fatal without emergency surgery. The AKC lists bloat among the breed's risks and advises against exercise immediately before and after meals. The best evidence on feeding comes from a US study of 1,637 large and giant breed dogs, which found that risk rose with age, with a close relative that had bloated, with fast eating and with a raised food bowl. The Bullmastiff was not one of the breeds studied, but the findings are the basis for current advice on feeding big, deep-chested dogs.

• Split the daily ration into two or three meals.
• Feed from a bowl on the floor, not a raised stand.
• Slow a fast eater with a slow-feed bowl, a puzzle feeder or kibble scattered on a mat.
• Keep walks and play away from meals, both before and after.
• If a close relative has bloated, tell the vet; family history raised risk in that study.

Signs of bloat are retching that brings nothing up, drooling, restlessness, pacing and a belly that swells and feels tight. Pale gums or collapse mean shock. Go to a vet immediately, at any hour. Ask the vet about a preventive gastropexy, often done at the same time as neutering, which fixes the stomach so that it should not twist, although it can still fill with gas.

Hips and elbows

Hip and elbow dysplasia are largely inherited, which is why breeders screen for them. Body weight affects how much damage a weak joint takes. In a lifelong study of Labrador Retrievers, dogs fed 25% less than their littermates developed hip osteoarthritis later and less often. That study was in Labradors, so the size of the effect in a Bullmastiff is not known.

For a dog that already has arthritis, supplements differ widely in evidence. A 2022 systematic review and meta-analysis found clear pain-relieving effects for omega-3-enriched diets and omega-3 supplements, but a marked lack of effect for glucosamine and chondroitin. Fish oil is therefore the joint supplement worth discussing with the vet; glucosamine products should not be relied on. None of them is needed in a young dog with sound joints.

Stiffness after rest, a swaying or bunny-hopping gait, reluctance to climb stairs or get into a car, or lameness in a young dog all need a vet examination. Pain relief and weight loss usually do more than any food change.

Hypothyroidism

Thyroid evaluation is part of the breed's screening. An underactive thyroid slows metabolism, and the Merck Veterinary Manual describes weight gain without more appetite, lethargy and exercise intolerance, with dry skin, heavy shedding and slow hair regrowth among early skin changes. It is most common between 4 and 10 years of age and usually affects medium to large breeds.

A Bullmastiff that gains weight on unchanged portions should have a blood test before its food is cut, because a diet will not fix a thyroid problem. Treatment is a daily thyroid hormone tablet, usually for life. Once the dose is right, energy and activity often improve, and portions need rechecking so that weight comes down steadily rather than overshooting. Iodine or kelp supplements should not be added in the hope of helping the thyroid.

A daily feeding routine

• Weigh the food: a kitchen scale is more accurate than a scoop, and at this size a slightly heaped scoop twice a day adds up.
• Weigh the dog monthly: a gain of 500 g a month is 6 kg over a year, more than 10% of a 50 kg dog.
• Count treats and chews: take them out of the day's calories, and prefer low-calorie training treats.
• Water: fresh water available at all times, in a floor-level bowl.
• Body condition: ribs should be easy to feel under a thin layer, with a visible waist from above. A heavy frame is not a reason to accept a rounded outline.

Sources

1. Bullmastiff breed information. American Kennel Club.
2. Nutritional Requirements of Small Animals. Merck Veterinary Manual.
3. Breed incidence of lymphoma in a UK population of insured dogs. Veterinary and Comparative Oncology, 2003.
4. Genomic Analysis of Lymphoma Risk in Bullmastiff Dogs. Veterinary Sciences, 2023.
5. Non-dietary risk factors for gastric dilatation-volvulus in large and giant breed dogs. Journal of the American Veterinary Medical Association, 2000.
6. Lifelong diet restriction and radiographic evidence of osteoarthritis of the hip joint in dogs. Journal of the American Veterinary Medical Association, 2006.
7. A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis. International Journal of Molecular Sciences, 2022.
8. Hypothyroidism in Animals. Merck Veterinary Manual.