The importance of genetic variation.
To genetically improve health, soundness and performance sporting dog breeders should select the individuals with the best breeding values to become parents of the next generation. In this way, the average performance of each future generation is increased.
The genetic quality of individual offspring, however, randomly varies around the mean (average) breeding value of the parents due to Mendelian segregation and independent assortment of chromosomes and genes. In other words, some offspring are genetically better than the mean of their parents, while other offspring are genetically below the average. For continued genetic improvement over multiple generations, parents that have a high probability of producing genetically outstanding offspring, offsprings above the average, are to be selected. Hence, apart from selecting parents producing offspring that do well on average, breeders’ goal should be to increase rates of genetic improvement by selection of parents that give offspring with greater genetic variation. In other words, genetic variation is desirable because it allows for the selection of above average progeny and increases the probability of finding a outstanding future sire or dam.
So the question is: how do we carry out the selections. First, is evaluating phenotypically the offsprings, starting with size and conformation, beginning as puppies and continuing into the second year of development. This also includes extensive field work observing all upland bird hunting traits for each individual. Ideally this should be accomplished on entire litters or nearly so.
Agricultural livestock producers have for at least two centuries used phenotypic selection, establishing a standard for various breeds. And racehorse breeders have additionally the performance records of the individual horse or mare and his/her progeny available extensively since the 1950’s. Field trial dogs have a small portion of those types of records although not as comprehensive and consequently not nearly as useful.
But in the last few decades a revolution has taken place in animal breeding. The use of genetic testing.
In beef cattle the genetic loci that determine ribeye area, determination of fat thickness and rate of gain are a few tests that are used. Also in wide use are genome test panels for more dependable heifer replacement decisions.
In milk cows genetic test panels by UC Davis determines the predisposition for producing three milk proteins using hair samples. And Zoetis US Diagnostics markets genetic tests for dairy cow wellness and fertility traits.
And there is the “Speed Gene Test”! Developed by Equinome that examines the myostation gene responsible for muscle development and muscle fiber type, helping race horse trainers select the suitable race distance for each horse. In fact, there are several genetic tests available worldwide to predict optimum race distance and optimum race surface(dirt vs turf) for individual horses.
How about genetic testing for canis lupis familiaris breeders? Our Llewellin setter testing group with the UC Davis Veterinary Genetics Lab (VGL) is the only sporting dog group aiming specifically at breeding strategies. The main thrust is reducing inbreeding, the number one cause of health and unsoundness maladies.
But the ability to measure the relatedness (and inbreeding) of each puppy in a litter has implications for enhancing the genetic quality of replacement brood bitches and retaining the best future stud dogs.
So while the vast majority of dog “breeders” stubble along with no genetic guidance, we and a few others are breaking new ground.