If you are a competitor looking for your next mount, unless you are conversant in bloodlines, then pedigree study is not going to help you too much. Instead you will look at the conformation of the prospective equines, evaluate their way of going and their performance record if they have one. And of course ride them yourself to see if they are a good match for you.
In contrast, if you are a breeder and want to be successful, pedigree study is of the utmost importance because the pedigree--if it is accurate--is the map of the genetics. And the genetics of your breeding stock and its planned mates is what you need to understand.
Conformation and performance are of great use to the breeder as well, but the can be deceptive and cause the paying of a stud fee or purchase price of a horse for your herd that will not help you reach your goal. So you need the tool of pedigree analysis in your belt, so you don't make costly mistakes.
Conformation evaluation is important; it represents the phenotype of the horse, and points to its best use and soundness. And there are wonderful resources out there, competent conformation experts like Judy Waldrope of jwequine.com who has several e-books available for purchase which teach the practical sport function represented in the physical points of the horse--with multiple photos.
Of course those of you who are invested in the European warmblood industry rely on the inspection process to set you straight about a horse's potential, trusting that the judge is impartial and knowledgeable. The inspection does include pedigree, but usually only the first three generations. If you have been part of that program for any length of time you came to realize that many of those inspection stars do little or nothing in sport; most just drop out of sight.
Part of the reason for this shortfall is that the inspection system of the warmblood societies operating here are based on their complete industry structure set in place in their own countries, that is, the horses that enter their inspections are just in the first step of their process, and the ones that do well are promoted then into their training and structured competition schedule, many purchased outright by the State registry. Their trainers, riders and instructors are employees of the system and the breeder is paid premiums, and the horses are virtually guaranteed the best chance to succeed and are brought along until they are sold to local or more likely foreign buyers...the inspection is just one part of an entire massive government run enterprise.
But here in the States horse breeding is not a government enterprise, and so unless you personally have a structured training regime, and competition schedule of your own, and the money to fund it, your inspection high scorer will never reach its potential. It might be a far better horse than those that make it through the European system in Europe, but in the States you are on your own to provide the next steps in the development of your stock.
Performance in our sports are the proof of our breeding decisions, and it has always been so here in America. Our racing industries are free enterprise and the proof of a potential sire is shown at the tracks. Our sport horses, traditionally called Hunters, were always trained and competed by their owners, proven in our various sports, hunting, steeplechasing, show jumping, horse shows, cross country trials etc. But it is always the individual, the breeder or competitor who pays the way. And unfortunately most of us cannot afford to play at the highest levels of our sport; we just don't have the resources to fund the trip.
But there is some good news for you coming from a 2010 Thoroughbred study done by Dr. Robert Losey and team, found in "Indentifying Broodmare Prospects for an Elite Broodmare Band". They discovered in evaluating large populations of racers, that a good performer, NO MATTER THE LEVEL, is a good candidate for breeding stock. They also found that a poor performer, no matter the level, is to be avoided.
Because the full financial burden is on the American sport horse breeder, no matter the system you employ, it is of the utmost importance that you do not breed junk. Unless you are very wealthy and can afford a hit or miss system by having huge broodmare bands to breed to your stallions, then you need to hit the bull's-eye each time you produce a foal. This is where pedigree study and analysis comes to the rescue.
I see a perfect example of the Losey et al report mentioned above and our pedigree points is found in the leading Thoroughbred stallion of 2014, 2015, 2016; this is Tapit 2001, a son of the good sire Pulpit out of Tap Your Heels. He was a good racer, nothing more. He won three of his six races, but only one of those wins was a stakes race, and he came in 9th in the Kentucky Derby. So how did this good, but not great horse become the best stallion in the country?
His pedigree tells the story. He is inbred 3x4 to Mr. Prospector through a son and a daughter (colt factor--see Understanding Pedigrees), 5x3 to Nijinsky through daughters (filly factor) adn 4x5 to In Reality through daughters (filly factor). This is a beautiful pedigree for a stallion, with strong dominances in the best lines, structured so that it helps the transmission of the traits to his offspring. His stud fee started at $15,000 in 2008, but each year rose because even though he was bred to less than top mares he began producing startling good racers, and when the quality of the mares rose, so did his results even more, and he has not stopped breeding wonderful horses. His stud fee was $300,000 by 2015 and his book is full.
So here is a horse that did well, but not great at the track, but had the potency to become a super-sire of top performers. You and I, even with limited resources can breed our own sport horse version of Tapit, or find an undervalued but potent sire to breed to. And we can look at potential stock that do well in the lower or mid-levels of our sports if we have the ability to understand their genotype through their pedigree. It is a wonderful tool and it levels the breeding playing field, so that you can produce the sport version of Tonalist (Belmont winner), Untapable, Frosted or Creator (top stakes winning progeny of Tapit). And do it time after time.
This website will provide basic outlines of the instructions you need, and if you are serious about breeding you will want to get North American Sport Horse Breeder for full step-by-step instructions and explanation in Tesio Methods.
Further, there is a resource page here where other sources and books are listed. Be aware many of the previous expert's books are out of print and hard to locate, but they are worth seeking out. Sometimes one appears on Amazon or Robin Bledsoe Bookseller and is reasonably priced and you can snap it up. Also try to find the references on the breed components you use in your sport horse recipe, it is important that you learn which of your preferred breed's bloodlines are potent in the traits you want to build into your herd. As you progress in your studies the pedigrees will begin to 'speak' to you and you will find it easier and easier to get that great horse you dreamed of.
If you are using Thoroughbred or Standardbred bloodlines or want to, you may want to pick up m books: Legacy of Lexington or Standardbred Sport Horses (see book info) because they cover those breed's lines from the sport horse breeder's point of view. You will be pleasantly surprised to find there is much more opportunity out there for your sport horse goals in our fine racing stock then you ever imagined and certainly more then you were ever told.