American Pit Bull Terrier Gazette Volume 44 Issue 3 | Page 4

A Look at Prepotent Brood Stock in ADBA History - Part III In my role at the ADBA doing pedi- gree analysis, I have the opportunity to study pedigrees and identify the breed- ing strategies being used by breeders of the past and those individuals produc- ing litters today. By dissecting a seven generation pedigree, it is really fasci- nating to see a glimpse into the plan- ning behind the famous dogs of the past and the litters being produced today. It takes two basic principals that breeders must consider in producing a quality litter. #1 is the selection of qual- ity brood stock possessing the traits that the breeder wants to see in the litter. #2 is following a breeding plan by look- ing at the pedigrees of those sire and dams and determining the mating that will give you the greatest probability of producing those positive traits that the breeder is attempting to produce in his litters. The goal should be to produce consistent and predictable traits in each litter. It has been said that an outstand- ing breeder is always planning ahead a few generations. That is the challenge and excitement of being a breeder of outstanding dogs. In the last issue of the American Pit Bull Terrier Gazette, I laid the ground work of the significance of the study of the “prepotent” sire and dams through- out the history of our breed. For those first time readers of the Gazette, and as a recap, let’s begin with the defini- tion of Prepotent. Prepotent is defined as having exceptional power, authority of influence. In terms of dog breeding, a prepotent sire or dam passes on their traits to a large number of their off- spring regardless to whom they were bred. The value of both a prepotent stud dog or brood matron can not be under- stated, but the far reaching effects to the breed as whole is greater in the case of a prepotent stud dog. This is due to the large number of offspring that can be produced by a stud dog compared to that of a brood matron. A review of the literature outlined the genetic basis of prepotence: Jay L. 4 Lush stated in his book Animal Breed- ing Plans that the most important genet- ic basis of prepotency depends first on homozygosity (alleles being the same at a given gene), then upon dominance, linkage and epistasis. A homozygous animal possesses the gene for a given trait from both his sire and dam and is genetically pure for that characteristic. Because the gene pairs are identical, this gene is passed on to every one of their offspring 100% of the time. A dominant gene is described as one of a pair of alleles (alternate forms of the same gene influencing the same trait but in different ways) whose effect is expressed over the effects of the al- ternate alleles. Every puppy receiving the dominant allele will show the effect of it. If the parent is homozygous for it, all of the offspring will be exactly alike for the trait expressed by the gene, re- gardless of the genetic material that they received from the other parent. Lush states, “When a parent having many dominant genes is also highly homozygous, its prepotency is MAXI- MUM.” Linked genes are those that are lo- cated closely on the same chromo- somes. Two or more characteristics are passed on together instead of randomly in the usual manner. Epistasis is defined as when a gene or a pair of allelic genes masks the expression of a different gene or pair of allelic genes. Epistasis is similar to dominance except the relationship is between different genes, instead of al- leles on the same genes. Because of its similarity to dominance epistasis is be- lieved to contribute to prepotency. Since Lush states, “The most im- portant genetic basis of prepotence is homozygosity” the next question to be answered is how does the breeder produce homozygosity in his breeding stock? Production of prepotent animals. Even though we see prepotent brood stock in lines that are not closely line bred and inbred, the breeder’s chief aid in producing a prepotent animal is through the use of these breeding strat- egies. The reason for this is that while dominance, linkage and epistasis of genes are not within the power of the breeder to control, he CAN control the homozygosity of his stock. The more closely related the sire and dam, the more rapid will be the increase in ho- mozygosity. Mating like to like without inbreeding and line breeding does little to increase prepotency. “The broad scientific definition is that inbreeding is the mating of animals more closely related to each other than the average relationship of the popula- tion concerned. When done properly and wisely it is of great assistance and using inbreeding vigorous prepotent animals of correct type are more rap- idly produced.” (Lush) Because of this statement, I believe that Lush is lump- ing styles of line breeding together with classic styles of inbreeding and refers to them all as inbreeding. He states that the mating of brother to sister is the highest form of inbreeding. Contrary to what most people believe because of the political hype against breeders, inbreeding and close line breeding does not create any weakness, defects or any of the physical or mental traits which will disqualify a dog from fulfilling its function. Inbreeding mere- ly exposes hidden recessive genes that have been present in the stock all along under the shield of their dominant al- leles. It does this by presenting them in a homozygous condition so they are expressed and made visible. By using inbreeding, the breeder is given an op- portunity to discover exactly what he- redity traits are carried by his animals. By bringing them to light, in some cas- es, he can completely remove from his bloodline those individuals that prove to be undesirable. A humane breeder can do this by spaying and neutering and placing in pet homes those dogs not acceptable as breeding stock. Ge-