Page 32 - 8 August 2012

The following letter was forwarded to Speedhorse by Dr. Gregg Veneklasen:
Dear Editor,
This note is in response to the opinion article provided by Mr. Larry Thornton in the July 6 issue of Speedhorse. Mr. Thornton is a well-respected pedigree analyst and his opinion is interesting. I believe that it remains highly important to combine fact and context with any controversial subject such as equine cloning. Most of us who are comfortable in roaming
the scientific domain of research can find supporting arguments for our point of view and we can lose the important balance necessary to take an honest look at a technical subject.
Mr. Thornton’s article begins to lose balance withthediscussionofgeneticdiversity.Itistrue that cloning could be used as a tool to concentrate the elite genetics within a breed and without responsible breeding practices could reduce the genetic diversity of the breed. However, all of
the breeding tools available to AQHA breeders today have the ability to create the same result with unimaginative and undisciplined breeding practices. The one primary difference that cloning offers versus the other advanced breeding practices already in regular use in the AQHA is that cloning is the most powerful breeding tool that can allow us to add genetic diversity from the desirable genotypes within the breed.
Cloning creates an opportunity to leverage
the genetics of proven geldings and to increase the supply of elite genetics from outstanding mares. Superior sires that were lost in the prime of their breeding careers can have their genetics rescued from total loss and placed back into full use. There is no breeding program or tool that will replace the ingenuity of a good breeder. A responsible breeder will assess the tools available and make the best decisions possible. It is difficult to imagine how the addition of sire line genetics from two- time AQHA World Champion Tailor Fit or Feature Mr Jess could be anything but positive for the breed.
Mr. Thornton is accurate when he states that the mtDNA haplotype of a cloned foal may not match the mtDNA haplotype of the donor, although by random chance sometimes it does. However, there are a few facts that one needs
to add to this discussion to form an educated opinion. These facts were omitted from Mr. Thornton’s article.
1) The mtDNA haplotype of a sire is irrelevant since the sire does not pass his mtDNA along to his offspring. Therefore, for the purposes of producing a breeding sire from a proven gelding or stallion, the current cloning technique reproduces the full breeding value of the original.
2) Thegeneralscientificviewontheimpactof a mtDNA haplotype is that it is highly useful to trace migration patterns of animals and humans over the previous centuries. In most modern breeding programs, we have replaced this need through extensive documentation. We no longer need to guess at the breeding patterns used to create change.
3) The physiological impact of the mtDNA haplotype is highly controlled by the nuclear DNA as they provide the majority of the instructions for activity. The bulk of the scientific community has concluded that
the mtDNA haplotype, as long as it is healthy, does not have a material impact on the phenotype of an animal. (See J Anim Sci. 2003 Jan;81(1):61-7 Van Vleck LD, Snowder GD, Hanford KJ. Also see J Anim Sci. 2003 Aug;81(8):1926-32. Hanford KJ, Snowder GD, Van Vleck LD. Also see J Anim Sci. 2005 Mar;83(3):552-6. Van Vleck LD, Hanford KJ, Snowder GD.
Also see J Anim Sci. 2011 Mar;89(3):693-8. Epub 2010 Oct 29. Garmyn AJ, Moser DW, Christmas RA, Minick Bormann J.)
4) In the absence of information regarding mtDNA haplotypes in the AQHA, ViaGen decided to conduct a study with the aid of a European mtDNA expert. We found that the mtDNA haplotypes of high performing AQHA horses were the mirror image of the mtDNA haplotypes found in our oocyte source. The single most common taproot mare for AQHA All American Winners is the “Unknown” mare. There is no common haplotype found to be concentrated among the winners. There are
a few haplotypes that are found at a higher percentage than others and quite often a cloned foal is produced with the same haplotype as the donor. Does this make the cloned foal more “identical” in phenotype than the others? This has not proven to be the case.
Mr. Thornton discusses the role of integrity within the breed. We should all strive to bring some level of integrity into this breed. However, discouraging a viable breeding tool that can
offer substantial opportunity does not promote integrity within the breed. In contrast, through DNA testing, we can identify many, many MISTAKES in the AQHA pedigree system. These mistakes should be identified and made clear to every breeder so that the mistake is not replicated. Certainly, more effort could be placed towards dealing with the genetic disease issues. As a breed, we need to embrace all technologies that allow us to work away from the ethical disaster that many of these genetic mutations represent.
In closing, other species such as bovine and porcine have much more advanced measurement programs to more fully understand the impact of their breeding decisions. They measure every possible attribute of an animal’s performance including fertility, birth weight, weaning
weight, average daily gain, feed conversion, mortality rate, etc. They convert these attributes into a formula to build a breeding value for
that animal. As a point of reference, all the major, influential breeds of bovine and porcine
32 SPEEDHORSE, August 3, 2012