In my previous post I listed 3 ways to help decide whether a sire carries the “X factor”. I should have included a 4th bullet point:
- From his pedigree. The presence of commonly agreed ‘X factor’ damsires in his maternal lines, and the production record of his dam, grandam and great-grandam will also indicate whether a sire has increased chance of carrying the X factor himself. It is more certain if his maternal line production statistics show a higher proportion of foals to starters/winners (and good winners), but also if the mare did this with a range of sires rather than just one, and if the successful horses are colts as well as fillies. This indicates that the X chromosone she contributes may be a dominant one and carrying quality genes. A sire that is a “one off” superb horse but not supported by some strong production statistics in his previous 2 or 3 maternal generations is much more of a gamble. Flashing Red would be an extreme example of this – a fantastic horse himself, but walking a fairly thin pedigree line.
However even with all the indicators flicking brightly, a sire can still be a disappointment at stud. This may be a result of getting mares with the wrong gene pool to complement his, or because of some other attribute he often passes on (fizzy temperament, conformation fault, lack of mental toughness, or just leaving bigger types that will take a lot of time to strength and mature).
So the X factor is just one of the things that go into the mix.
Refer to the articles that Ray Chaplin and I put together on Rich N Elegant and her siring sons for an example of this puzzle.
I’m not an expert in this at all, and I would love to hear from others who have more experience than I do – do you think the X factor is over-rated? What is the importance of heart size in today’s harness racing?
b4breeding 
Hi and thanks for your reply to my question re X Factor sires. Yes i totally agree that this is subjective,but could be another piece of the puzzle to make the picture complete with correct breeding standardbred procedure.
Love to hear peoples thoughts.
Regards.
KevinD
Yes it is a fascinating puzzle. There is objective evidence, and I gave the ways I would look for that evidence. But I’m careful how I interpret it. It isn’t as simple as a list. For example, I presume (but will find out) that pressure from owners prevents studs from releasing a sire’s heart score. But even if studs were able to provide that information, it could easily be misinterpreted as saying the sire is going to be a dud, when that is not necessarily the case at all. His colts will be depending on the mare’s genes for heart size. And an average heart may be all a horse needs if it has the desire to win, great gait and a good trainer! And heart scoring itself has its pros and cons, differing methods etc which would make a consistency and comparisons difficult.