There is no guarantee of good genetic health of any dog, purebred or otherwise, as not all damaging genes are recessive. Also, of course, purebred and mixed-breed dogs are equally susceptible to nongenetic ailments, such as rabies, distemper, injury, and infestation by parasites.

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Mutliple generations of mixed breeds can result in mongrels with no distinct breed markers, such as this dog with chow chow, labrador retriever, and terrier traits, among others.

Types of mixed breeding

It's important to note that all dog breeds are man-made creations: dogs were traditionally bred for specific functions. All existing dog breeds began as mixed breeds, either by random occurrence or by deliberate crosses of existing breeds. Encouraging desirable traits and discouraging others, breeders sought to create their ideal appearance or behaviour, or both, for dogs, and, additionally, to ensure that the dogs could consistently produce offspring with the same appearance or behaviour. Some consider mixed breeds undesirable, but mixing breeds can lead to desirable results, especially in the hands of an expert breeder. On the other hand, inexperienced cross breeders can produce disastrous results. For example, the offspring of an obsessive Border Collie and an energetic, destructive Terrier could be dogs whose behaviour is so erratic as to make the dogs a liability.

Mixed-breed dogs can be divided roughly into three types:

• Crossbred dogs, which are mixtures of two known breeds. Some crossbreeds have traits that make them popular enough to be frequently bred deliberately, such as the Cockapoo—a cross between a Poodle and a Cocker Spaniel—and the Labradoodle, which mixes a Labrador Retriever with a Poodle. Other crossbreeds occur when breeders are hoping to create new breeds or to add or reinforce characteristics from one breed into another breed. Most crossbreeding, however, occur accidentally.

• Mixes among more than two breeds, such as when a crossbred dog mates with a purebred dog or with another crossbreed. The term mongrel is sometimes used to distinguish these dogs from crossbreeds.

• The generic canis familiaris, seen in feral or pariah dog populations, where mixed breeding has occurred over many generations. These dogs tend to be light brown and of medium height and weight. This "genetic average" might also represent the appearance of the modern dog's ancestor.

There is no scientific justification for the belief that a purebred bitch is in any way tainted after mating with a dog of another breed. Future mating with dogs of the same breed will produce purebred puppies.

Mixed breeds in dog sports

Both purebred and mixed-breed dogs can excel at dog sports, such as obedience, dog agility, flyball, and frisbee. Often, highly energetic mixed-breeds are left with shelters or rescue groups, where they are sought by owners with the caring, patience, and drive to train them for dog sports, turning unwanted dogs into healthy, mentally and physically stimulated award winners.

Historically, conformation shows and dog sports excluded mixed-breed dogs from competition. While this tradition is changing, some sports still remain open only to one breed of dog, such as greyhound racing, or to one type of dog, such as sheepdog trials open only to dogs of known herding ancestry. In the latter case, herding organizations now sometimes accept mixed-breed dogs who have evident herding-dog ancestry, such as Corgi mixes or Border Collie crosses.

Until the early 1980s, mixed-breed dogs were also generally excluded from obedience competitions. However, starting with the American Mixed Breed Obedience Registry (AMBOR) and the Mixed Breed Dog Club of America (MBDCA), which created obedience venues in which mixed-breed dogs could compete, more opportunities have opened up for all dogs in all dog sports. Most dog agility and flyball organizations have always allowed mixed-breed dogs to compete. Today, mixed breeds have proved their worth in many performance sports.

Some kennel clubs, whose purpose is to promote purebred dogs, still exclude mixed breeds from their performance events. The AKC and the FCI are two prominent hold-outs. However, the AKC does allow mixed breeds to earn their Canine Good Citizen award.

In conformation shows, where dogs' conformation is evaluated, mixed-breed dogs normally cannot compete. For purebred dogs, their physical characteristics are judged against a single breed standard. Mixed-breed dogs, however, are difficult to classify except according to height; there is tremendous variation in physical traits such as coat, skeletal structure, gait, ear set, eye shape and colour, and so on. When conformation standards are applied to mixed-breed dogs, such as in events run by the MBDCA, the standards are usually general traits of health, soundness, symmetry, and personality. The Kennel Club (UK) operates a show called Scruffts (a name derived from its prestigious Crufts show) open only to mixed-breeds in which dogs are judged on character, health, and temperament.

Advantages and drawbacks

The mature appearance and behaviour of purebred puppies is more predictable than that of mixed breeds, including cross-breeds. With purebred dogs, the genetic variations are well documented and a breeder has a fair estimation of what type of offspring a given pair will produce. Even still, there is variation within breeds; for example, two champion sheep-herding Border Collies might produce offspring with no interest in sheep herding.

Mixed breed dogs are, on average, no more intelligent than purebred dogs, and both sets feature both slow learners and dogs with high learning capacity. For example, Benji, the hero in a series of films named for him, was a mixed-breed terrier. However, it is more difficult to predict the trainability of mixed-breed dogs when they are very young. Most Golden Retrievers are eager to please, but a mix of a Golden with the independent Siberian Husky could inherit either dog's trainability—or you could get a dog with the endurance and athleticism of the Siberian and the trainability of the Golden.

Many people enjoy owning mixed breeds, valuing their unique appearance and characteristics; while dogs of some breeds, such as the Tervueren, exhibit little variability of appearance, mixed-breed dogs exhibit often unique appearances. Although some dog owners have a specific breed of dog they wish to acquire, and will never accept a mixed breed, many others enjoy mixed-breed dogs that exhibit characteristics similar to their favourite breeds; in fact, with a mixed breed, they can enjoy some aspects of appearance and personality of two favourite breeds with a single dog.

There is usually an abundant supply of mixed-breed dogs wanting owners, available at negligible prices, while pedigreed dogs can cost hundreds or thousands of dollars and reputable breeders can be hard to find.

Some owners value a dog's pedigree as a status symbol and, therefore, have no use for mixed-breed dogs, whose market value is effectively zero; others particularly appreciate the physical or behavioural traits of certain breeds; still others ignore pedigree and, instead, value a dog's personality and health. In short, most dog owners believe that their dog's breed—and specifically his or her own dog—is the best sort of dog there is.

Finally, one of the best sources for both purebred and mixed breed dogs are your local animal shelters. The cost is low and many of the animals are housebroken.

References