Genetic testing is a vital part of maintaining an honest breeder registry.
For every gene, there are different versions called “alleles” that exist. The alleles determine things like coat color, polled/horned, etc. The GENOTYPE tells you which TWO alleles the Dexter in the lab. The PHENOTYPE shows you, in real life, the visible or producible genetic trait that comes from the alleles present.
So again the genotype is what the Dexter is on paper ( Like Pc/Pc.) The phenotype is the observable trait as it looks like on the Dexter (A Dexter genetically with no horns.)
The best for the Dexter breed, would require us to consider both genotype and phenotype, when evaluating our herds. Some would say genotype shouldn't matter at all and the Dexter's physical appearance show be all that matters. An example of where this would not be fully true is in the genetic testing for milk traits that promote better cheese making. There are some Dexters that produce low levels of beta-lactoglobulin and high levels of kappa-casein which are associated with better protein, fat and casein yields for cheese making. If you don't test you won't know what your Dexter carries. Dexters that produce milk this richer milk may produce calves that have better growing yields. Oftentimes, the good phenotype of some Dexters is passed over or overlooked because their genotype doesn't match up with the current market. This is an unfortunate outcome for those Dexters who's alleles visibly produced a great looking animal. Another example of when it can be deadly, if just relying on the phenotype of an Dexter, is when determining if the Dexter is a carrier for Chondrodysplasia. Not all carriers carry the “short legged” phenotype. If you breed a carrier cow with a carrier bull you risk the chance of having a bulldog calf ( Dead deformed calf.) The bottom line is consider your preferred genotype result, test for necessary genetic genes and don't forget the importance of phenotype, when selecting a Dexter. If you do all of that, you better your chances of having a good outcome on your ranch.
Currently there are two labs in the US that provide our breed with genetic testing.
The only test that is required to register a new animal in the ADCA is “Parent Verification.” This test proves that the new calf is an offspring of this ADCA cow and this ADCA bull.
Picture below shows you how to determine possible offspring genetic outcomes based on the sire/dam testing
You can apply the below example to other double gene results, so long as you follow the proper crosses on each column and row.
What does obligate mean in terms of genetic results? You may hear a breeder say, “ Oh this calf if obligate for Chondro and PHA.” The breeder means that because the sire and dam of the calf BOTH had the same results, then the calf can ONLY be that result too. There are some situations where this needs to be teased out further. An example of that is the polled genetics. A new breeder may say both parents are polled, so the calf is obligate for polled too. This may not be true depending on “What polled genes” the sire and dam carry. As you can see by the example in the Punnett square above, even if a polled sire/dam have a phenotype trait of polled, that does not mean that the offspring will be polled too, which is why you must know those alleles to know for sure.
