Selective Breeding

What separates "good" and "reputable" breeders from "bad" and "backyard" breeders is SELECTIVE breeding. No matter what controversies may exist about breeding ages, line breeding, adoption fees, caging, culling, etc., one factor that is really solid and incontrovertible to me is that breeding must be done selectively, with a purpose, goals, not only knowledge of inheritance but that knowledge put to use. Anyone not breeding selectively cannot be considered a breeder, because no or little thought has gone into the breeding and the line. They are simply bringing more animals into this world with no improvements to their health or temperment or anything. (DISCLAIMER: While you may not find much information in this article, this is my personal thoughts and ideology--which I rarely get to share. So please use it how you wish, and recognize that this is just my own opinion...)

My personal definition of selective breeding is "the art/science of recombining genotypes for a desired effect." A pretty definition, but very complex when put into practice. Remember that one cannot "SEE" a genotype, only a phenotype, and a phenotype can have many causes--especially when looking beyond mere appearence and into issues such as health and temperment--the important issues.


Natural and "Artificial" Selection

Natural selection is the scientific theory that explains the ability of animals to adapt to changing environments and needs. While the theory cannot be entirely observed (though evidence is abundant) in nature, it has been in practice thoughout the history of animal domestication. Breeding domestic animals and "selective breeding" is "artificial selection." This is essentially the same thing as natural selection, but instead of future generations being selected by environmental factors, they are selected by people to fit into a "domestic niche" (my own terminology ;-) ), such as guarding a home, hunting rabbits, pulling a cart, use in a laboratory, or being a gentle pet. It is "artificial selection" that makes a shih tzu different from a labrador, for example.

Selection started long before the time of Darwin. People kept only the most friendly wolf cubs and wild cats in their homes. People bred their best hunting dogs to get more of the same. People selected sheep with the wool they prefered, horses that were faster, etc. without any true knowledge of heredity. Genetics, in all its complexity, is, at its raw and most basic level, a matter of common sense. If an animal has undesired traits, you don't breed it, because those traits could be passed on. Regardless of whether you are outcrossing or inbreeding, you need to consider every aspect of the animals and their lines, and be honest with yourself about which traits are desirable, which are undesirable, which can be easily bred out, and which are serious enough to consider ending a line or not breeding from a certain group.

The mystery comes with things that "skip a generation," carried traits. Now that we know about genetics, we can predict recessives, and even breed for them. Recessives don't actually "skip a generation," but they can theoretically be carried for many generations without showing up, and then finally "reappear" when an animal is bred to another carrier. In other words, it is not enough to know an animal's parents. A breeder must know the grandparents, great grandparents, and other relatives to successfully start and improve a line.

Factory breeders (aka "puppy mills" or other "animal mills") have abandoned selection. They put two animals together or even just leave whole groups together for the purpose of large numbers of offspring, which translates to profit. Backyard breeders (the people who want to try breeding one litter or they have a male and female so decide they should "let them" breed--or breed to a neighbor's animal) do not practice selection either. They may say things like, "My rats are so healthy and friendly, I know thay'd have great offspring." But what about the parents of those rats? The grandparents? The great grandparents? How much is hereditary and how much is their care/experiences? And how old are these rats? If they are less than a year and a half old, there is no way to tell how "healthy" they are, because cancer, liver disease, diabetes, and many other problems linked to heredity don't set in until old age. (We must rely on parents' and grandparents' health to make health decisions about a line). If they are less than a year old, you have no way to know their "temperment." Young nervous rats sometimes calm down with age, but more significant is that "biters" are wonderful and friendly animals in their youth, but suddenly the aggression kicks in (around 8 to 12 months) and they can become so vicious that they can't be touched without biting hard.--THIS BEHAVIOR IS HEREDITARY. It is important for anyone considering breeding to be aware of that.


Uses of Pedigrees and Probability

Must we bring math into this? Well, yes, and no. Probabilities do not always help us predict the outcomes of a litter, but they allow us to know what is possible and what is impossible. They also can be used to help identify a "mystery" color especially in large litters.

A pedigree listing only the names and colors of the rats is of limited use. Most pedigrees are designed like this. It caan help you predict colors and types, but beyond that, it doesn't really help you out much unless you have records on those individuals that you can access or you can remember those rats clearly. Responsible breeders probably remember every minute detail of every rat they have bred. The breeder will be able to tell you the personality and health of any rat listed in the pedigree (that they owned) or tell you about the breeder that they got the rat from. Most responsible breeders also have a vet, who will have health records for any visits or procedures.

In short, pedigrees are very valuable to breeders, but as just part of the overall record-keeping process. Keeping good records is essential to developing good lines. Pedigrees provide the road map for where you started, how far you have come, and help you decide where you can go from here.


Making Tough Decisions

So, we choose good rats to breed and make informed decisions to better our lines, but a responsible breeder is one who knows when not to breed. Selection is not simply choosing the rats to breed; a big part of it is choosing which rats not to breed. While we love all our rats and can see the good sides to them, we need to be realistic and be able to say "He is a good pet, but he should not be bred."

In nature, the weaker animals that won't contribute "good genes" to future generations do not survive to reproduce. Natural selection is why wild rats are "standard agouti." It isn't that other mutations (albino, beige, rex, hairless) don't occur, but these traits are not beneficial to survival, so the rats don't survive to breed. "Old age" health issues are not a factor in wild populations, because wild rats don't get old. When they start to slow down, they become easy prey. Natural selection dictates which animals will be successful at bringing about a new generation and really nothing else.

Our pets, however, do survive. The strong survive; the weak survive. They all survive unless they have very severe defects. It is our moral duty to take care of our pets, whether weak or strong, so their survival should not be seen as "bad." However, they do not breed unless we allow that to occur, and we should not be breeding animals that are weaker.

If a severe congenital problem occurs in a line (such as diabetes or megacolon), a breeder must be able and willing to stop breeding the close relatives of that animal regardless of how nice a color or type they might have. It might be tough to end a line you have worked on for several generations, but some problems cannot be bred out or SHOULD not be attempted to breed out. (Remember, while you are dabbling in "breeding out," many generations of animals may suffer.)


Communication, Shows, and Registries

Selective breeding cannot be done in complete seclusion. Breeders will get nowhere if they try to reinvent the wheel over and over again. With the internet and digital cameras, rat shows, expos, travel, etc., breeders have ample opportunity to discuss the results of breedings, the problems in lines, and what genes can cause certain effects on colors and markings. Beginning breeders and also well-established ones need to seek second opinions about their lines, so they can improve their line with a wealth of information and feedback. Breeders should NEVER view each other as competition! We are working (or should be working) toward a common goal: healthy, friendly, and attractive pets.

Some show clubs have lost sight of their purpose. Shows were created to allow communication between breeders and give them an unbiased look at how "good" their lines are and how they can improve them. Unfortunately, clubs have formed competitive relationships with each other (based on the "controversies" mentioned in the first paragraph on this page), and shows themselves can set up a competitive atmosphere, which can hurt the fancy as a whole. But, keep in mind, that if breeders all view clubs and shows as tools for better breeding, they can have enormous benefits.

There is another unfortunate side effect of shows, the spread of disease. Since rats do not have readily available vaccinations like cats and dogs do, shows and any contact with other rats or rodents pose a very real threat to them. While proper quarantine can minimize the risk, it cannot be completely eliminated. So breeders have to choose between the health of their animals (and potential risks) and the valuable feedback and interactions at shows. Because of these problems, I do not believe a person can "judge" a breeder based on whether or not they belong to clubs or go to shows, but they must be able to communicate with other breeders by some means!

Registries are also valuable tools--that can be abused. They allow long records and pedigrees and encourage the sharing of health information. Databases can allow breeders to look beyond their immediate line to distant relations in the pedigree. The problems arise when people are misled into thinking a registered animal is "better" somehow, or a person provides false information, or a "competitive breeder" uses the health records to try to discredit another breeder. When you use a registry properly, it is one of the best tools a breeder can have. Breeders need to be honest and not feel afraid to share details on all aspects of a line, especially the faults. Only by knowing our faults can we improve our lines and be able to breed selectively.

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