Breeding for Fun and Profit - but not much else.
Imagine for a moment that you are offering your loving Cocker Spaniel a treat. As your hand approaches her mouth, she suddenly gets a distant look in her eye and stiffens her posture. Without warning, she attacks your hand viciously and then backs off. Instead of continuing to threaten you, she has a dazed and sheepish look on her face; as if she is unaware of what she has done. If you think your pet is crazy, you may be right. If you think her problem is a genetically inherited disorder, you may also be correct.
Breeding purebred animals is an old tradition. For thousands of years, animals have been selected for particular traits. From the fantastic sense of smell of a blood hound to the flat nose of the Persian cat, selective breeding has retained the best examples of these traits - and the worst.
While some may chose to breed their pets, many are ignorant of the complexity of doing it correctly. The common perception is that you can take a pretty female and breed her to a good male and get "pretty-good" pups. This is like breeding a white dog to a black dog in order to get grey puppies. Unfortunately, breeding is never that simple.
To illustrate the difficulty of breeding healthy animals, pretend you are a German Shepherd breeder. As with many breeds of dogs German Shepherds sometimes suffer from a genetic malady called hip dysplasia -- the result of the incomplete development of the hip socket. This condition often leads to complete disablity. To breed dogs that will not have dysplasia you must first find a bloodline that is free of the defect. After you find these dysplasia-free German Shepherds, you breed your litter, secure in the knowledge that you will have healthy pups. Sounds pretty simple, right?
Unfortunately, genes don't mix like paint. Of the eight pups in the litter, two still carry the genes for dysplasia. Two are free of dysplasia, but carry genes for epilepsy. Two of the other four pups will grow to be exceptionally fearful. The final two are relatively free of genetic defects -- and indistinguishable from their litter mates. When the time comes to decide which pups to keep and which ones to sell, you will be unable to tell which two are the keepers. Oops.
Dedicated to impoving the breed of German Shepherds, you decide to breed again, since two pups are free of epilepsy. Your next litter is a success and you do avoid any pups with genes for epilepsy -- and get a litter that develops diabetes - and dysplasia. According to "Medical and Genetic Aspects of Purebred Dogs" by veterinarian Ross Clark and Joan Stainer, there are at least 25 genetic defects common to German Shepherds.
German Shepherds are not alone in this genetic Russian Roulette. Miniature Poodles have over 26 known hereditary diseases, while Labrador retrievers have at least 25. Even the best breeders have difficulty isolating healthy breeding pairs.
Cats do not escape this dilemma either. Flat faced cats like Himalayans and Persians have a full set of teeth scrunched into a tiny jaw. Their nasal passages and sinuses are often malformed. Dental and respiratory problems are common among these cats.
Some obvious physical defects in cats seem inconsequential. Polydactylism describes cats born with many toes. Their feet look like baseball gloves. This disorder does not debilitate the cat . Manx cats, from the British isles, are born without a tail. This seems harmless but may be a serious problem. Some tailless cats are also born without the proper nerve network in the rectal and anal regions. The result is a cat that may not have any ability to control its bowels.
Two other serious hereditary problems for cats are deafness and epilepsy. White cats with two blue eyes have about a 50% chance of being deaf. Epileptic cats may show no symptoms of the disease until they are adults.
The attraction for particular breeds of domesticated animals is universal. Each culture has developed its own image of what a cat or dog should look and act like. Along with the wonderful physical and behavioral traits that have been passed down, grave illnesses and maladies have come along too.
The expertise to breed healthy, genetically sound animals is a rare commodity. Good breeders are dedicated and educated people who take every possible precaution to prevent birth defects. Before breeding animals for fun and profit, consult your veterinarian and experienced breeders to find out what it takes to do it right.