Mixed Breed

Origin and purpose

Mixed-breed dogs live all over the world. They come from any mix of breeds and non-breed dogs and were not bred to a single standard or job, so they have no AKC group or popularity rank.

DNA tests can estimate a mixed-breed dog's breed ancestry, and genetic panels can screen for known disease-linked gene variants. Treat the results as a clue, not a diagnosis: the researchers behind one large study caution that finding a disease-linked variant in a dog of a different genetic background does not confirm the dog will develop the disease. Share any health findings with your veterinarian rather than changing your dog's diet or care on your own. (PLOS Genetics)

Ancestry results won't tell you how much to feed, either. Knowing your dog is part Labrador or part Chihuahua doesn't set the portion; your dog's actual weight and body condition do. (WSAVA calorie chart, WSAVA body condition chart, Pet Nutrition Alliance)

Coat and energy

A mixed-breed coat can be any length, texture or color, depending on the dog's ancestry. Energy varies just as much, so it isn't rated here: base exercise and treat plans on your own dog's activity and body condition, with your veterinarian's input.

Nutrition and weight

Portion by weight, not by breed. There is no typical weight for a mixed-breed dog; WSAVA's calorie chart for healthy adult dogs, for example, runs from 4.4 lb to 107.8 lb (2 to 49 kg), and the right amount at either end is very different. Weigh your dog and ask your veterinarian what a healthy weight is for that dog. (WSAVA calorie chart)

Next, check body condition. WSAVA's chart uses a 9-point scale with 4 to 5 as ideal: you can feel the ribs without a heavy fat covering, see a waist behind the ribs when looking down from above, and see the belly tuck up from the side. As the score climbs from 6 to 9, the ribs get harder to feel, fat builds up over the lower back and the base of the tail, and the waist and belly tuck fade and then disappear. AAHA's 2021 guidelines recommend that the veterinary team look at nutrition at every exam, ideally scoring both body condition and muscle condition, so ask your vet to show you how it's done on your own dog. (WSAVA body condition chart, AAHA)

Calorie charts and formulas are only a starting point. WSAVA notes that some dogs need more or less than its chart suggests, and the Pet Nutrition Alliance says individual animals can differ from formula estimates by as much as 50%, so the amount fed may need to go up or down to reach or keep an ideal body condition score. Merck treats any daily feeding amount as a first estimate to adjust through ongoing checks of weight and condition. Talk with your veterinarian before putting a dog on a weight-loss plan. (WSAVA calorie chart, Pet Nutrition Alliance, Merck: feeding)

Merck also notes that leaving food out all day works for only a minority of adult dogs, since most would become obese, and advises counting the calories in all treats for dogs prone to weight gain. Being mixed-breed doesn't rule out weight problems: obesity was one of the 20 most common specific diagnoses among dogs at primary-care clinics in England, and a lower group average says nothing about your own dog. (Merck: feeding, PLOS ONE)

If you have a mixed-breed puppy and aren't sure how big it will get, ask your veterinarian which growth food fits. A Tufts veterinary nutritionist explains that large- and giant-breed puppies are more sensitive to too much or too little calcium while their bones grow, that pet food label rules treat dogs expected to weigh 70 lb or more as adults as large-size, and that some argue 50 lb is a more cautious cutoff. (Tufts)

Health watch

Being mixed-breed is not a health guarantee either way. A UC Davis study of 27,254 dogs with inherited disorders found that 13 of 24 conditions showed up at about the same rate in mixed-breed and purebred dogs, 10 were more common in purebreds (for example elbow dysplasia and dilated cardiomyopathy) and 1 was more common in mixed breeds. (UC Davis)

• Cranial cruciate ligament rupture: A tear of one of the main stabilizing ligaments in the knee. In the UC Davis study, which covered dogs seen at its veterinary teaching hospital from 1995 to 2010, it was the only one of the 24 conditions that turned up more often in mixed-breed dogs than in purebreds. No specific treat link. (UC Davis)
• Carrier status for inherited recessive disease variants: In a DNA screen of 83,220 mixed-breed and 18,102 purebred dogs, mixed breeds were about 1.6 times as likely as purebreds to carry one copy of at least one of nine common recessive disease variants (30.3% vs 18.4%), while purebreds were about 2.7 times as likely to carry two copies and be genetically affected (3.9% vs 1.4%). The most common variants in both groups included ones linked to degenerative myelopathy, a form of progressive retinal atrophy (prcd-PRA) and hyperuricosuria. Which variants a given mix carries depends on its ancestry. No specific treat link. (PLOS Genetics)
• MDR1 (multidrug sensitivity) gene mutation: A gene change that can cause severe, sometimes fatal, reactions to certain common medications, such as some parasite preventives, sedatives and pain relievers. Washington State University's diagnostic lab lists an approximate mutation frequency of 5% for mixed breeds and 10% for herding-breed crosses (versus 70% for Collies), says it is less likely in a mix but still possible, and recommends testing to learn a dog's risk. The 2018 DNA study also collected numerous reports of mixed-breed dogs carrying one copy, some of which took up to four days to recover from anesthesia. No specific treat link. (WSU, PLOS Genetics)

Common problems for any dog: in the study of dogs at primary-care clinics in England, outer ear inflammation (otitis externa), dental disease and blocked anal sacs were the three most common specific diagnoses across all dogs (about 10%, 9% and 7% of dogs), but none was more common in crossbreds. Purebreds had a higher prevalence than crossbreds for 3 of the 20 most common diagnoses (outer ear inflammation, obesity and skin lumps), and the other 17 showed no significant difference. (PLOS ONE)

No single life span fits all mixes. Most earlier research has found crossbred dogs living longer than purebreds, though not every study agrees, so your own dog's size, weight and health matter more than a label. (Scientific Reports)

Fun fact

In a 2018 DNA screening study of more than 100,000 dogs, mixed breeds far outnumbered purebreds: 83,220 mixes versus 18,102 purebreds from 330 breeds. The same common disease-linked gene variants turned up in both groups. (PLOS Genetics)