Avoid a lifetime of pain and suffering for your pet.
Most of you have heard it said a mongrel is healthier than a purebred dog. That is a myth. There are hundreds of inherited diseases in purebred dogs but there are also genetic risks in all animals including mixed breeds of dogs, whether accidental or selective, which can be avoided with a little bit of care and knowledge about genetics and better managed by selective breeding by professional breeders.
Science has provided us with a genetic blueprint and breeders now have the ability to avoid inherited genetic problems. Why should we sentence these loyal friends to a life of pain and suffering?
When dog breeders mate dogs where both have recessive genes which cause disease or other flaws, they are being part of the problem. If the dogs which are being bred both have a recessive gene which causes a physical or other problem, the statistical probability of that problem showing up in a pup is 1 in 4 EVEN if both of the parents are healthy and do not themselves manifest the deficit or disease. Inherited diseases that do afflict dogs are most often the result of recessive traits carried by the parents of those pups.
In one study, Professor Donald Patterson at the U of Pennsylvania was able to trace 21 separate inherited diseased to recessive genes, including hemophilia in some Terriers, central nervous system disability disorders in Springer Spanels and muscular dystrophy in Golden Retrievers. There is a gene that causes narcolepsy in Doberman Pinschers and Labrador Retrievers - which is the same sleeping disorder found in humans.
Where these problems show up the most are in puppy mills, where lots of dogs are constantly interbreeding, and lots of those dogs which may contain recessive genes for disease are constantly passing those genes on to those poor pubs. Purebred OR NOT; it is just sloppy, irresponsible breeding.
There is no good reason why dogs should be subjected to genetic risk when we have the tools to combat those problems now. There is no good reason why we should as a society which cares, tolerate puppy mills or breeders who ignore genetic disorders in favor of profits.
Dogs were the first animals to be domesticated and considerable diversity have been uncovered in prehistoric archaeological sites. Dogs have especially been depicted in paintings and on pottery found in western Asia and in the Middle East. One of the earliest foundational breeds from these depictions has been the greyhound and medieval hunting and guard dogs.
BUT distinctive breeds appear to be a modern manifestation and along with them genetic diseases which were inherited as traits which were selected artificially by breeders.
To understand the problem of selective breeding it is necessary to know a little bit about inheritance and genetics. The laws of genetic inheritance were first formulated by an Austrian monk, Gregor Mendel in the 1860s, who did most of his research using peas however the results were found to be applicable to other more complex life. The Mendelian laws demonstrated how individuals can act as carriers for certain traits (or diseases) where the parent organisms do not themselves show those traits.
According to Mendel's genetic inheritance, traits from parents DO NOT BLEND in children but remain separate and recessive genes occur statistically in offspring - whereas DOMINANT genes are ALWAYS expressed in offspring.
The following is excerpted from the Canine Inherited Disorders Database of the Canadian Veterinary Medical Association and funded jointly by the Animal Welfare Unit at the Atlantic Veterinary College and University of Prince Edward Island:
(quotes)
"The dog has 78 chromosomes, in 39 pairs, on which approximately 100,000 genes are located. This makes up the animal's genotype. The phenotype is what you actually see in the animal, and this can be influenced by both environmental and developmental factors. For example, a dog's size as an adult is determined partly by his or her genes, but is also influenced by environmental factors such as its health as a puppy and the food it eats."
"Each gene in a chromosome pair has a partner at the same position (or locus) on the matching chromosome. Each member of a gene pair is called an allele. A gene can have many alleles within a population but an individual animal will have only 2 alleles which influence a particular trait. If the 2 alleles are identical (AA or aa for example), the individual is homozygous at that locus; if the alleles are different (Aa), then heterozygous."
"If the allele is dominant, only 1 copy is required to express the trait; if recessive then 2 copies..."
"A disease condition or abnormality may be caused by many factors. Some of these are genetic; that is the disorder is a result of a mutation in a gene that carries particular information. Some mutations are spontaneous, such as a mutation caused by toxins consumed by the mother during pregnancy. An inherited defect is one in which the defective gene has been inherited from one or both of the parents."
"Many conditions that have a well-documented hereditary basis may also have other causes. For example, there are several forms of hereditary cataracts, but cataracts may also occur as a result of injury, toxins, or a disease such as diabetes. In trying to determine whether a disorder is inherited, your veterinarian will look at many factors, including the age the disorder becomes evident, whether littermates or other relatives are affected, and whether the defect is known to occur in that breed. It is very important that inherited disorders be identified so that information can be relayed back to the breeder, and on a larger scale, so that breeding programmes can be designed to reduce or eliminate these debilitating conditions in dogs."
(end of quotes)
Breeds that have an increased risk; that is, have a predisposition due to genetic inheritance should be a concern of any breeding program to reduce those problems - to reduce the possible (and probable) harm and pain to the offspring. It should be a serious responsibility of any good breeder to avoid any harm which may come from their breeding. Profits alone should not determine mating. Eventually, since laws determine a social ethos, there should be strict penalties for breeders who ignore the consequences of their actions.
Dog breeds are relatively new subdivisions in the species when it was considered useful or just plain cute to breed for specific characteristics. Breeding, it can produce traits which are also not a benefit. The trait which is desirable may also include some which are not.
Dogs sweat through their paws. It is common for dogs but arctic wolves have no functional merocrine or apocrine glands. Sled dogs, not wolves and their paws tend to "snowball" which is when ice and snow balls form on their paws. The animals suffer; they're in pain and they are sometimes injured.
Usual taxonomy for same species animals is if they reproduce together and their offspring can reproduce they are the same species. Dogs however, can reproduce with wolves, coyotes, jackals and of course, other dogs. They are interfertile which suggests there has been evolutionary hybridization of these species. Nevertheless, they are separate species though in the wild there is continued cross-breeding.
There are 38 species classed in the family Canidae, which includes foxes, jackals, dingos, wolves, dogs, zorros, dholes, et al.
Genetic testing have indicated that domestic dogs, despite their breeds, are virtually identical to others in their genus Canis, though all are classified as separate species.
According to an unpublished paper at Hampshire College (Braun, 1990) there were greater (Mitochondria DNA) "mtDNA differences appeared within the single breeds of Doberman pinscher or poodle than between dogs and wolves. Eighteen breeds, which included dachshunds, dingos and Great Danes shared a common dog haplotype. Alaskan malamutes, Siberian huskies and Eskimo dogs also showed up in the common dog haplotype and were no closer to wolves than poodles and bulldogs. These data make wolves resemble another breed of dog." (Prof James Serpell, The Domestic Dog, 95 - Cambridge U Press)
"To keep the results in perspective, it should be pointed out that there is less mtDNA difference between dogs, wolves and coyotes than there is between the various ethnic groups of human beings, which are recognized as belonging to a single species..." (ibid)
And as mentioned above, "as-if" we were talking about a single species, which we are not, these animals are all interfertile, which would ordinarily classify them as one major prerequisite for classifying them as being in the same species. Of course it would be rather difficult to get a 100 lb Saint Bernard and a 4 lb Chihauhua to breed (but it is possible to transfer sperm or to have an in vitro union and cause it to happen).
But, who would want to?
(They're often more loyal and better friends than people)
Getting back to dominant and recessive traits, much damage has been done by indiscriminate dog breeding. A breeder should be aware of the consequences of passing on deleterious genes. With natural selection that which survives to produce and out-produces others is successful at influencing the gene pool, but with unnatural selection undesirable traits can be passed on as recessives and not be noticed or dominate genes can damage the immediate offspring. At the very least it can cause a lifetime of misery and pain.
Called autosomal dominant, one copy of a gene which is inherited from either parent if in either parent that affected gene is dominant the trait will be passed on to approximately ONE HALF of all offspring. Remember, there is no blending; that is not how it works. Individual offspring will be affected. In this case the dominant trait is apparent in the parent and it will be apparent in an offspring.
If a condition is apparent obviously the parent should not be used for breeding. In many instances there is incomplete dominance. That is, the trait caused by the gene has only variable expressivity. The offspring are susceptible to the disorder if either parent carries the gene - but not all of the offspring will be affected equally. Alternately, there is also an incomplete penetrance of the dominant trait. When the penetrance is 75% approximately 3/4s of the offspring which inherited the trait will also express it.
Called autosomal recessive, the most COMMON inheritance of genetic conditions the offspring inherits each copy of the gene from both parents. The offspring may appear normal but will be a carrier of the affected gene and will pass it on to its offspring, some of which may be affected and some will be carriers also. If a carrier the affected gene will be passed on to half the offspring. If the offspring of carrier offspring is mated to a normal dog without the affected gene the offspring will be normal - BUT, they will also be carriers. If TWO carriers are mated, 25% of the offspring will be affected.
Example: Progressive retinal atrophy (PRA), which causes blindness in many breeds is one such trait which can be passed this way.
"As long as the frequency of a gene for a recessive disorder remains low in the population, the particular gene may be passed along for many generations before by chance 2 carriers are mated and affected individuals are born. However, the gene frequency may become unusually high due to breeding of close family members, or because of the "popular sire" effect, where a sire with a harmful recessive gene is mated frequently because of desirable traits." (from Canine Inherited Disorders Database of the Canadian Veterinary Medical Association)
"Because the recessive gene is carried in the population in outwardly normal animals, it is very difficult to eradicate these traits. However the incidence can be reduced by identification of carriers through test matings or through various tests that have been developed, and the conscientious use of this information in breeding programmes. Veterinarians, dog breeders, and breed associations must all work together for substantial progress to be achieved." (ibid)
It is obvious a breeder must know what they are doing. If in doubt, don't breed them; JUST LOVE THEM.
Leave the Breeding to Professionals
There are other patterns of inheritance which we know about thanks of course to Gregor Mendel but also all the other research which has gone into this important issue.
There are many specific patterns of inheritance where some breeds are said to have breed predisposition for those traits.
Some traits are sex-linked. Some are Mitochondria DNA related and some are nucleus DNA related.
Some traits are from genes on the X chromosome. Males carry one X chromosome from their mother (bitch) and 1 Y chromosome from their father (or sire). The Y chromosome carries little more than the information for the offsprings maleness. Female offspring have 2 X chromosomes and get one from their mother and one from their father. If the mother is a carrier for a recessive gene (the notation is Xx) and she passes the recessive gene (x) to her daughter, the daughter is an unaffected carrier - but her poor male offspring who get the gene from their mother will be affected.
There are other more complex interactions which I won't go into here, but I recommend any with pets who may breed them to consult their veterinarian first, especially if you know there have been problems with their blood line for any possible inherited diseases. I really strongly suggest you leave the breeding to those who do it professionally and have your animals fixed. It is healthier for them also.
If you love your animals, and obviously you do, make sure you do the right thing by them and make sure they receive the very best nutrition you can afford - and DON'T over-feed them because they were once scavengers (when your cave brother relatives kept dogs as pets and hunting partners) so it is kinder to withhold food than to let them eat as much as they can hold (and they will). Exercise them too. Love them. They love you back. You will never have a more loyal friend.
As stated in the beginning of this essay, it is a myth that purebred dogs are "weaker" than mutts. Stay away from puppy mills. They're in it for the money and it's the animals that suffer.
A sick animal or badly bred animal will cost you and it will be painful for the animal. It is not cheap caring for a sick animal (or any animal) and anyone who has a pet is obligated to provide as much care as that animals needs.
And it simply is not true that mixed breeds are healthier and less suseptible to diseases anymore than pure bred dogs, however cross breeding between packs may result in additional gene variation, which can be either good or bad, depending on the possibility of gene defects in DNA which may be caused by recessive genes or by mutations; including mutations from radiation, oxidative stress and all of the other opportunities which exist in nature which could be inherited. On the other hand, careful breeding by "informed" breeders can produce healthy and robust animals.
Hank Roth
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Excerpts provided here are pursuant to the Fair
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for educational and discussion purposes per
Title 17 U.S.C. Section 107,
Copyright Law.
Today is Saturday February 04, 2012
