Buckpasser versus Mr. Prospector

[aethervox]

Regarding the post where I quoted "Buckpasser is easily the most influential thoroughbred sire in today's pedigrees when attached to the female line." I did save that particular information before the website changed, and will attempt to summarize as best I can.

According to the author, George William Smith, at ten major North American horsetracks (Santa Anita, Del Mar, Fair Grounds, Churchill Downs, Keeneland, Gulfstream Park, Aqueduct, Saratoga, Belmont and Woodbine) in 2016, there were 1223 horses racing who had Buckpasser as the broodmare sire of their 4th dam. He only sired 148 producing mares, so that means there were 8.25 horses running in 2016 / each producing mare foaled by Buckpasser. Buckpasser died at 15, so had a short stud career.

The next closest sire to Buckpasser in the table is Round Table, who had 1235 horses racing in 2016, out of 177 producing mares, giving a ratio of 6.98. Round Table lived to age 33.

Princequillo was a bit of a surprise to me, since his first crop of foals was in 1946, yet he was the 4th dam's sire of 1283 runners in 2016. He sired 214 producing mares, which made his ratio 6.0;

Mr. Smith considers War Admiral "superior", even though his ratio is 3.44, because his first crop was in 1941, but he still had 561 horses racing in 2016 where he was the sire of their 4th dam.

The other superior sires between Round Table (6.98) and Princquillo (6.0) are Hail to Reason (6.54), Native Dancer (6.5), New Providence (6.41), Better Self (6.19) Bold Ruler (6.17) and Amerigo (6.06).

He does point out that his results need to take into consideration how close to 2016 the sire was foaled. He also mentions that Mr. Prospector's first crop was in 1976, but in 2016 his ratio was only 0.70 with 372 horses running from 533 producing mares. Quite a difference from Buckpasser whose first crop was only 7 years earlier.

My interpretation is that if a stallion in the 5th generation-tail female has a significant number of descendants running, it's an indication of how good his daughters, granddaughters, etc. are - at least they were considered good enough to breed another generation.

I haven't been keeping up with the latest research, but has anyone done any research to see if any specific genes might linked to 'elite' performance in races that are longer that a mile and a quarter? I think that would be where a larger heart would be more advantageous to a horse.

[Pan Zareta]

My interpretation is that if a stallion in the 5th generation-tail female has a significant number of descendants running, it's an indication of how good his daughters, granddaughters, etc. are - at least they were considered good enough to breed another generation.

Based on Buckpasser's performance as general and broodmare sire, as well as his subsequent distribution throughout TB pedigrees past and present, my interpretation is that he's among the secondary targets of positive selection pressure from his time period, whereas his temporal peer (roughly) Mr. P., is clearly among the primary targets of same, regardless of his shortcomings in the 5th generation pedigree position of 4th damsire.

I haven't been keeping up with the latest research, but has anyone done any research to see if any specific genes might linked to 'elite' performance in races that are longer that a mile and a quarter? I think that would be where a larger heart would be more advantageous to a horse.

There's a lot of journal literature available based on genome-wide association studies, some of it reporting association of certain genetic variants with specific distance ranges and/or elite performance, but no mention of heart size. The variants in the MSTN complex on ECA18 (which account for many of the reports available) may be of some relevance to heart size though not all of them have any significant association with class at any distance and MSTN appears to have far less effect on cardiac muscle v. skeletal muscle.