What Is Inbreeding and Line Breeding: And Their Importance?

We begin this article first by defining the word Inbreeding.

Inbreeding the production of offspring by parents more closely related than the average of the population. Genetically, inbreeding increases the portion of homozygous genes in the inbred population.

Line breeding is a form of inbreeding in which an attempt is made to concentrate the inheritance of someone ancestor, or line of an ancestor in a pack.

It gives me great pleasure to share a topic with those of interest in defining this subject of dog breeding. As a genetic major and master breeder I bring forth this article because so many people in the dog business are raising dogs and you always hear the comment "Oh, he inbreeds his family." Well I share this article with you so that before you make a comment, at least you should know what the words mean and how they can be used in a positive way to help the breed we so dearly love, the Jack Russell Breed!

Inbreeding is a mating system in which progeny are produced by parents more closely related than the average of the population from which they come. Example A: The mating of a Father to his daughter

Example B: The mating of a full brother to a full sister.

These procedure are avoided because past experience has shown that inbreeding is usually associated with the appearance of genetic defects and a general overall decline of vigor and performance.

In humans, it is believed that children from the marriage of first cousins are doomed to be deformed physically or mentally, and this belief is the reason we have laws to prohibit the marriage of close relatives.

The genetic effect of inbreeding is that it makes more pairs of genes in population homozygous regardless of the kind of gene action involved. All phenotypic effects of inbreeding result from this one genetic effect.

Inbred animals are usually less able to cope with their environment than are non-inbred animals. This is shown by their ability to reproduce and the litter size declines along with slower growth rate and small body size at maturity. You will also see a weakening in the immune system that will cause more diseases and illness within these inbred individuals. Some of the other negative effects we Jack Russell breeders really need to look at is jaw line, how the teeth line up in our puppies and by which the families and the individual we use we can identify progeny with any other defects early.

Now we move on to the topic of line breeding and its benefits. Line breeding is a form of inbreeding in which an attempt is made to concentrate the inheritance of one ancestor, or one line of ancestors and is usually a male rather than a female because a male generally produces many more descendants than a female. Line breeding is usually a mild form of inbreeding that is directed toward one ancestor which often involves half sibling mating. It can also be used as close as a grandfather - grand-daughter mating or an uncle - niece mating. Again you will be increasing the genetic traits of the sire you wish to use. I think this method will be beneficial to help understand the definition and their use in any breeding program. But again we must always strive to produce as structurally correct and genetically sound Short Legged Jack Russell Terrier that we can all be proud of.

For instance, some of the traits we should avoid when mating our Short Legged Jack Russell Terrier are excessive length of back and poor quality legs that are not straight and sound. We always would prefer a dog whose ear fits his head and folds down not upright. Again we must watch the jaw line for over and under bites. We must also keep in mind the depth of body capacity and the openness of their rib cage, after all this is where the puppies will be carried. Again you want a dog that has a wide base width when viewed from the rear. This also effects the birthing process. And again you want a prominent vulva on your females because the more correct we make our dogs the longer their breeding lifespan and overall health will be enhanced. This again will ensure you and your client of a puppy you will both be proud of!