Since the introduction of DNA testing - and as more information becomes easily available through the Internet - horse folks and breeders are better able to make responsible decisions concerning equine genetic disorders. They potentiallyexist in every breed of horse, but since it is Quarter Horses we raise here, we are focused on them in particular.The ‘5-Panel Test’ as it has been dubbed, has been available since 2007 and is conducted by the University of Davis (UC Davis) in California, USA. The test kit can be ordered through AQHA by the breeder/horse owner and is sent directly to UC Davis, with an enclosed ‘postcard’ also going to AQHA to notify them that the kit has been submitted. The resultsare sent directly to AQHA who, in turn, notifies the breeder/owner; and records the results on the horse’s permanent record at AQHA.It should be noted that there are other agencies available for equine DNA testing (including colour testing); however, to the best of my knowledge UC Davis is the only institute currently under contract with the AQHA (2013).The genetic disorders that are commonly tested for in Quarter Horses are: HYPP, HERDA, GBED, MH and PSSM1. Some of these disorders have been traced back to a particular Stallion. For example, HYPP first showed up in the offspring of Impressive, an extremely prolific sire popular among the Halter Horse crowd for his size and exceptionally heavy muscling. HERDA has led back to Poco Bueno, and PSSM1 is suspected to have started with King P234, although other sires are rumoured to be involved also. An excellent article on Genetic Disorders in Quarter Horses and Related Breeds, written by Heather Smith Thomas in 2009, can be found here:http://www.onlinedigitalpubs.com/publication/?i=18672&page=1&p=357It should be emphasized that having one of these sires in a horse’s pedigree does not automatically mean the animal carries a disorder. Because they are passed genetically (and are often a Recessive trait), these disorders follow the same rules for Mendel’s Law as colour genes do (see Basic Genetics). Passing generations have bred out the faulty gene in many cases, and now a days, informed breeders are eliminating them further through selective and responsible breeding. The key words here being ‘informed’ and ‘responsible’... and that is what the ‘5-Panel Test’ is for.When we first started our breeding program, we decided that, if we wanted to call ourselves ‘responsible breeders’ we had to look at every aspect of our breeding stock, from bloodlines and conformation to eye appeal, to ensure we were producing the best examples of the breed that we could. Good conformation and disposition were key... rare colour was grand... and DNA testing to avoid producing offspring with genetic disorders was essential. After two years of carefully selecting each mare and stallion, we waited with baited breath for the results of their 5-Panels to come in. Sadly, one of our favourite mares came back positive as a carrier of both HERDA and PSSM1, so weremoved her from our breeding program. Dancer is now my favourite riding horse. She’s a lovely girl, pretty and good natured - but, unfortunately, she will not be bred.
Note: In Spring of 2013 the American Quarter Horse Association (AQHA) past new regulations that require all stallions exposed to 25 or more mares during the 2014 breeding season to have a genetic disease panel test on file with AQHA prior to the registration of their foals resulting from breedings occurring after January 1, 2014. Additionally, the Stud Book and Registration Committee recommended that ALL stallions will be required to have a genetic disease panel test on file with AQHA prior to the registration of their foals resulting from breedings occurring after January 1, 2015. These new rules are denoted as Rule REG108.4 and REG108.5 in the 2014 AQHA Official Handbook of Rules and Regulations.