Grading up is an interesting and useful process that can be used for DSS breeders.
It is one sure way to ensure the breeds survivability over long centuries of purebred breeding. Understanding what upgrading is and how it affects a breed genetically are extremely important issues of breeders of all purebred breeds.
Grading up is the sequential use of purebred animals over a series of generations to provide a “nearly purebred” result. The usual sequence is that a purebred sire is used on females that are either crossbred or of another breed. The resulting offspring are 50% or 1/2 (Grade 4) the pure breed of the sire. The daughters are then mated back to another sire of the breed, providing offspring that are 75% or 3/4 (Grade 3) the pure breed. The next generation provides offspring that are 87.5% or 7/8 (Grade 2), the next is 93.75% or 15/16 (Grade 1), then 96.875% or 31/32 (Grade 0).
Only the female offspring from graded sheep can be registered until grade 0 has been achieved at which time, after inspection, both males and females may be excepted into the “pure” flock book.
Grading up has been widely used in a number of livestock species, especially with recently imported breeds. It allows for rapid numerical expansion of the breed, and also provides a demand for purebred males (generally) for crossbreeding.
Grading up has lots of positives, a few negatives, and has several facts that make it an interesting biological phenomenon.
As a backdrop to this issue it is important to reflect on the character and utility of breeds. Breeds are useful because they are reasonably consistent genetic packages. That is, they have certain combinations of genes that are repeated throughout the breed, and this consistent genetic makeup makes breeds reasonably predictable. It is the predictability that is the key to the value of breeds, for without predictability it is impossible to match breed to place, purpose, and system. So, anything that conserves the aspect of breeds as consistent genetic packages tends to be helpful, and likewise anything that detracts from it is detrimental.
At higher levels of grade, which includes grade 1 and 0, the influence of outside genetic material is minimal, and the animals are performing and breeding like most purebreds. These upgraded animals may have a slight advantage in overall vigour, and in fact do offer breeds enough of a breath of fresh air (or fresh genetics) that can be a great advantage to some very rare breeds, while at the same time posing minimal threat that any of the genetic uniqueness of the breed will be lost.
Grading up, if carefully managed and monitored, can assure that pure-breeds remain viable and vital, and also can assure that they retain their status as genetic resources.
The grading up program will be carefully monitored by DSS(UK) to assure that appropriate levels of grade are achieved before inclusion of animals into the purebred flock book.
Grades of DSS are defined as follows:
Grade 0 – over 96.875% DSS genes
Grade 1 – over 93.75% DSS genes
Grade 2 – over 87.5% DSS genes
Grade 3 – over 75% DSS genes
Grade 4 – 50% DSS genes
The grade and percentage will be shown on the registration certificate.
DSS(UK) may, at its discretion, upgrade to 100% those female Grade 0 DSS with over 96.875% DSS genes into the “Pure” flock book.
All percentage female DSS are eligible for registration within the register.
Only Male DSS that are 96.875% or over (grade “0”) are eligible for registration and at the discretion of the DSS(UK), upgrade to 100% DSS and entry into the “Pure” flock book.
On acceptance of a registration by DSS(UK), owners will be issued with a pedigree certificate for each DSS showing its registered number and indicating the grade and percentage.
All forms and certificates issued and received by, or on behalf of, the DSS(UK) shall remain the property of the DSS(UK).
All Grade 0 DSS will be subject to inspection by a charity trustee of DSS(UK) on a random basis. If any sheep is found not to conform to the relevant breed standard on inspection its registration may be changed or withdrawn.