Genetic Change, Part One: Selection Accuracy
Part One of Genetic Change: Rules and Tools focuses on selection accuracy. Stay tuned for the next three parts of this series.
Selection accuracy is important if any improvement or gain is to be made. This means the traits you select for must be heritable, and the animals you choose for parents must have high breeding value for the traits under selection. For instance, if you select for a heritable characteristic, such as fleece weight, you must use stud males who historically have produced offspring with higher than average fleece weights. The same goes for fineness, crimp, staple length, etc.
The following chart is the most recent from the AOA EPD program. As you can see, the commercially important traits are highly heritable. Any trait that is in excess of .40 percent heritable is considered to be moderately heritable verging on highly heritable. Although fleece weight is under .40 it is generally considered moderately to highly heritable in most fiber animals. I believe that lower number is due to variability in shearing methods and how people report the weight; some people do not shear and report the entire fleece.
HERITABILITIES USED IN THE LATEST EPD CALCULATIONS FOR HUACAYA AND SURI
|Average Fiber Diameter (AFD)||.52||.52|
|Standard Deviation of AFD||.52||.52|
|Percent of Fibers larger than 30 microns||.55||.52|
|Standard Deviation of Curvature||.55||.20|
|Mean Staple Length||.39||.15|
If you purchase foundation stock, replacements, or breeding services, and fleece weight is your goal, you must ask for records of shear weights for all the male’s offspring and inspect as many of those offspring in a given environment as possible. Or better yet, before you buy breeding stock, you might want to ask if the breeder has EPD’s for the trait under selection.
EPD’s and Selection Accuracy
By inspecting the EPD, you determine the breeding value of the parents. Parents with high EPD’s for a trait assure a higher degree of selection accuracy for the progeny.
There are four ways or tools to help make accurate selection decisions:
- Phenotype: Many breeders believe they can look at an alpaca – its fleece style, size, show winnings, etc. – and assess the breeding value of the animal under selection. Phenotype is the least reliable way to make accurate breeding decisions. Selection by phenotype alone results in accurate decisions less than 50% of the time.
- Pedigree: Many breeders study pedigrees and swear that they can use them to make accurate selection decisions, and they do help, especially if there is line breeding or close relationships in the pedigree. Pedigree, when combined with phenotypic evaluation, results in accurate decision about 60% of the time.
- Assessing Progeny: Most breeders do not assess a representative number of a parents offspring, but it is scientifically established that if they were to analyze just eight progeny together with their phenotypic analysis and a review of the pedigrees, their accuracy would increase to about 85%.
- EPD’s: It is a scientific fact that adding EPD’s to your selection decision increases the accuracy of your selections to over 98%.
You can argue these points all you may, but the science is settled. Ignore it at your own peril. Ask yourself which percentage of accuracy would you like to be reflected in your breeding decisions: 50%, 60%, 85% or 98%?