SDP LC01 race 13SP

Breeding To Win

SDP 5gen-graphicEach individual in a pedigree contributes a certain percentage of genes to the foal. Increasing the percentage of blood of a specific horse through inbreeding increases the probability of that horse’s traits being present in the foal.

Plummer groups all of those factors and more into two main categories – genotype and phenotype. Genotype is defined by Merriam-Webster as “all or part of the genetic constitution of an individual or group.” A horse’s pedigree, his family, and all of the characteristics and traits they carry is his genotype. Phenotype is “the observable properties of an organism that are produced by the interaction of the genotype and the environment.” The phenotype is what an individual actually shows, such as conformation, temperament and soundness. Both, he says, are equally important.

“The genotype is everything that you can’t see, and the phenotype is everything that you can,” Plummer said. “To me, it’s 50/50. Outstanding geno and phenotype horses are vital to having success as a breeder. If you want to increase your odds of success – and that’s what breeding is, a probability game – you should breed your top geno and phenotype horses.”


When Plummer starts to look at a horse’s genotype, what he’s really doing is studying the genetics in its family tree. Knowing the individuals within the pedigree and knowing their prepotency is key.

“Certain horses are prepotent for certain things,” Plummer said. “What are the High Brow Cat’s known for? They’re known for being very trainable and having a natural draw. That’s kind of their signature thing. The Peptoboonsmals are known for having big stops, the Dual Reys for being extremely cowy and athletic. Each family can have different prepotent traits; they have their strengths and minuses.”

Once you’ve decided what your end goals are for the foal you are trying to produce, you can select the prepotent traits that are more apt to get you there. Tesio did this by analyzing the race records of generations of Thoroughbreds. Plummer takes a similar path in the Western performance horse world, relying on show pen results and breeding statistics.

Plummer will look at the statistics for each individual horse in at least the first five generations of a pedigree. Planning a successful mating, he believes, depends on much more than just one stallion and one mare. Each individual in a pedigree contributes a certain percentage of genes to the foal – a percentage that can be increased by linebreeding.

“The sire and dam are going to contribute 50 percent each,” Plummer explained. “The second generation has four horses that have 25 percent each. The third generation is 12.5 percent each, and so on and so forth. If you have linebreeding and inbreeding within those five generations, then you simply add up those percentages. So if you have a horse in the third generation, which is 12.5 percent, and you have that horse again in the fourth generation, which is 6.25 percent, if you total that up, then that horse is responsible for 18.75 percent of blood within that individual. What that does is show you what probability of traits that horse can throw into the baby.”

SDP LC03 MrSanPeppy QHN

Despite a difference of 40 years and several generations, Mr San Peppy’s (top) influence can be clearly seen in TR Dual Rey (bottom).

SDP LC04 TRDualRey 09CJackson

Combining the greatest number of prepotent traits in an individual’s genotype increases the odds of producing a superior animal. One of Plummer’s favorite examples of that on his own farm can be found in TR Dual Rey’s pedigree.

“It’s fascinating to me when I look at TR Dual Rey. He has Mr San Peppy in his pedigree through four generations, four times. So [TR Dual Rey] happens to be on a dosage of 31.25 percent of Mr San Peppy’s blood. It all happens to happen in the third and fourth generations, which is pretty dilute, but when you stack the deck four times in that pedigree in those four generations, that’s the dosage.

“So if you look at a picture of TR Dual Rey, who was born in 1999, and you look at a picture of Mr San Peppy, who was born in 1967, it is amazing. There’s 40 years between those two horses, and yet they’re still so alike.”

In addition to linebreeding, Plummer also gives heavy consideration to hybrid vigor, the Rasmussen factor and magic crosses. Hybrid vigor is the positive influence that can be gained by introducing different families into a pedigree, or outcrossing. The Rasmussen factor, named after the late Daily Racing Form columnist Leon Rasmussen and his colleague, Rommy Faversham, describes inbreeding to superior female families through different individuals. The inbreeding must occur on both sides of the pedigree, and within five generations. A magic cross is a pedigree mix that has been proven to be successful time and time again, such as Wimpys Little Step on Smart Chic Olena mares.


When Plummer starts talking about the importance of phenotype in selecting breeding stock, he likes to tell a story he often saw played out on his father’s racehorse farm.

“Someone would come to him and say, ‘I’ve got this filly and I’ve had her in training for six months, and I’m just not getting any success with her. So I’m going to retire her and I’m going to breed her.’ What they’re really saying is, ‘I’ve got a horse that’s really slow and I want to raise babies out of her so they can be slow, too.’” Plummer related. “You’re going to breed what you have, but don’t start yourself out in the hole, because she contributes 50 percent of the genes. If that’s all you have, make sure you breed the other 50 percent of the genes to fill in for all of her weaknesses.”

In other words, breed the best mare you can afford to the best stallion you can afford, within reason, always keeping in mind that genotype and phenotype work hand in hand. Breeding for one at the expense of the other is rarely successful.

“Jesus was a pretty smart guy when he told us the parable of the olive tree. If you have your bad branch, it’s not going to give you good fruit, and the good branch will give you good fruit,” Plummer said. “You know, that can be translated into breeding just the same way. If you breed to a freak that has no genotype behind it, how likely are you going to get another freak? Not likely, because it has no family behind it to support it.

“The same thing could be said about really well-bred horses that weren’t good individuals. If you want to increase your odds of success, then breed to superior individuals, both what they are and where they came from, not necessarily what’s trending right now. What’s happening in 2014, when you are making that decision of who to breed to in 2015, isn’t necessarily going to be successful in 2019, when you have the results of that breeding.”

Plummer enjoys using his skills and expertise to help Buffalo Ranch clients, and has already played a role in starting the career of two stallions – TR Dual Rey and Hydrive Cat – with leading freshman sire status. That’s quite an accomplishment, given the fact that the four-year timetable from conception to show pen makes it difficult to quickly test new breeding theories. Plummer has found an interesting way around the time factor through one of his hobbies – breeding racing and show pigeons.

“I’ve learned far more breeding my pigeons than I ever will with horses, just because of the fact that their gestation is so much shorter than horses,” Plummer said. “The economics of the horse industry are such that whoever is making that breeding decision might not be the one who ends up caring for that horse, putting it through two years of training and putting it with the right hands to end up being in the show pen. That, to me, is where it gets a lot harder, versus my racing pigeons, where I’m breeding them and then four months later I’m racing them. The time frame and the economic end of it is much easier for me to see the results. So that’s why I’m a much more confident breeder, because I have the experience of I made this decision and I got this result. It takes much longer and much more money with horses.”

Also, a lot can go wrong from the time a foal is born until it steps into the arena at a major futurity. It takes a solid two years of training to get a horse to that point, during which time fate may step in with a twist that keeps a promising prospect out of the show pen. While statistics are still important, Plummer doesn’t always let the lack of a show record deter him from a horse he thinks will contribute to his breeding program. As long as the horse shows the phenotype Plummer is after, and has the genotype behind it, it could still make the cut as a breeding animal.

“We all know if you put a male and a female together, well you’re going to get a baby. But what kind do you want? You want more than just four legs, two ears and a tail,” Plummer said. “I wish it was as simple as taking stallion A and you cross it with mare B and what you’re going to get is baby C. But if it was that easy, it wouldn’t be very fun either. I wish mating selection was a science, but it’s really more of an art form. It’s pretty rewarding and it’s fun.”

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