Page 24 - NMHBA Summer 2017

And what if that same choice is made over and over? Is there a subsequent effect on the breed’s gene pool? Does it expand or does it shrink? Do we wind up painting ourselves into a breeding corner? And, even if we find a stallion who is a blank slate outcross, would he get enough mares to pay his bills?
There are very few situations that do not carry at least the possibility of unintended consequences. Now, 16 years after the AQHA authorized the use of frozen semen, those unintended consequences are emerging.
First, we need to interject a little sidebar to this story. Originally, the frozen semen rule stated that said semen could be used to breed mares only until the end of the year in which the stallion died. So, a stallion who died October 7, 2004, could continue breeding until December 31, 2004. As things have turned out, the rule should have retained that time restriction. But, in 2010, with almost no fanfare, it was changed to allow frozen semen from a deceased stallion to be used indefinitely – right down to the last 829th straw.
The early Quarter Horse was similar to the country doctor, who made his rounds from cabin to cabin, treating everything from a sore throat to amputating a gangrenous leg. Those progenitors of
the Quarter Horse breed were jacks of all trades and masters of many. They could put their rider in the perfect spot to rope a cow and then return to drive a bellowing group of cattle along a barely visible trail. Later in the day, they could line up with one or two other horses and blister across a 300-yard “track” in the middle of nearly-nowhere.
The performance diversity of these
early horses was a by-product of their genetic diversity. Their veins bulged with the inherited blood of Thoroughbreds;
of the tough, compact Indian ponies that left their homelands with their owners to re-settle in Oklahoma; and the Spanish horses that carried explorers into the New World. It was an undeniable genetic wealth that was massaged and manipulated and molded for the next 200 years.
A lot of things happened during those two centuries, with one of the more notable transitions being specialization. The country doctor turned into a physician who treated only feet and another into
an expert on digestion. One-room school houses grew into sprawling campuses with teachers specializing in English or math or biology.
Horses followed suit and, over time, Quarter Horses found themselves listed in one of six subgroups. They are: racing,
A genetic study was conducted with rigorous culling to create as much diversity as possible, the findings of which show that unlimited use of frozen semen restricts and shrinks the gene pool, increases chances of in-breeding, and can lead to over-population.
reining, cutting, halter, working cow and western pleasure. It was found that specific groups of individuals were (are) used
to produce the highest level performers
in these six groups. On face value, this would seem to indicate a shrinkage in genetic options. Fortunately a genetic
study, paid for in part by the AQHA, was commissioned in 2012 - 2013. The research team hired for the project came from the University of Minnesota. One of the leading team members was Dr. Molly McCue, a veterinarian and geneticist at the University. Dr. McCue grew up with ranch-bred Quarter Horses and remains a breed fan.
The first step was to lay out those six subgroups named in the above paragraph. Dr. McCue started the research with her own opinion, saying we were probably doing several things that were limiting genetic diversity within the six sub- populations. Furthermore, she felt this
was especially true in the last 25 or 30 years. One of the research markers was to determine the extent of the in-breeding in these six groups and, further, forecast what could happen if we continued with the industry’s current breeding practices.
The team isolated the top 200 performers from each of the six groups. They used a money-earned in 2009 and 2010 as the criteria for selecting the top 200 in reining, working cow, cutting and racing. AQHA points earned were the criteria for halter and western pleasure. Half and full siblings were eliminated from each group. The goal of this rigorous culling was to create as much genetic
diversity as possible. Next, 24 random individuals were selected from each group for a total of 144 horses.
Both genetic and pedigree analyses were gathered on all 144. The team focused on 65,000 genetic markers and five-generation pedigrees.
The test findings paint an interesting and detailed summary of the breeding segment of the industry.
According to Dr. McCue, the six performance groups clustered into three genetic groups. The racing sub-population stood out on its own genetic platform.
The pleasure and halter horses clustered together; the working cow, reining and cutting individuals stood together to form the third group. Groups such as halter
and racing shared no common sires, while reining and working cow did. The most common 15 sires across all the groups were all tail-male descendants of Three Bars TB. And, several of those 15 stallions’ pedigrees showed more than one Three Bars crossing in the first four generations.
It’s important to understand that the word “diversity” is equal to the level of genetic variation in a population. Using both pedigree and genetic analysis yields a more detailed picture. In this particular study, the lowest genetic diversity was in the cutting and racing subgroups.
So, what are we really doing in terms of the genetic pool?
In essence, the indefinite, unlimited
use of frozen semen (and especially when combined with multiple embryo transfer) can be compared to the mass production
of a variety of products. The more popular the product, the more they’re produced. HD televisions enjoyed sky-high popularity when they first hit the marketplace.
They were very expensive, compared to pre-HD models. Today? How about a 60-inch HD, ready for all those wonderful trappings such as Netflix and Hulu, for a mere $500? Basically, we Quarter Horse folks have been mass producing certain bloodlines for several years, thereby severely restricting and shrinking the gene pool while simultaneously increasing our chances of in-breeding. Additionally, we’re creating (again, especially when we include multiple embryos in the equation) a serious over-population problem. A sad reflection of said over-population is one report that states 70-percent of the horses in kill pens are Quarter Horses.
Dr. McQue summed up the situation perfectly when she said, “We are changing the genetic landscape in the Quarter Horse within the top level performance groups... Any time we take a single individual and
22 New Mexico Horse Breeder