pattern of inheritence of the X factor

[stancaris]

Someone on another board posted that it makes sense to use the large heart trait as one that is autosomal dominant (Hh). I said that it doesn't make sense because a large hearted sire (Hh) would pass on the large heart to 50% of his sons and daughters and that Haun never observed such a pattern in her research. Furthermore, if the trait were autosomal dominant then a homozygous stallion would pass it on to all his sons and daughters. No such pattern was ever observed.

What are your thoughts on this matter?

[louis finochio]

When you in-breed or line breed to the same immediate family you will get TB with small heads and small frames, including hearts.

When you outcross you will get TB with large frames and large hearts.
Barbaro is an example of this, as his pedigree is an outcross of NP sire lines.

[stancaris]

Do you think that a large heart is an autosomal trait or a sex linked trait carried on the X chromosome?

[xfactor fan]

Louis, what you are seeing is inbreeding depression. Inbred anythings have more identical pairs of chromosomes than other members of their species.

Think of this as a genetic handicap. The inbred horse is carrying an extra 25 lbs. The trick is to select the best inbred horse for breeding then outcross.

Stan, I think it is X linked. As for Secretariat, the poster boy for the X factor, there were most likely at least 3 things going on.

1. He got the large heart X from his dam and broodmare sire Princequillo.

2. He was a mosaic, in that some of his cells carried an extra mutation for heart size, hence the large heart. His germ cells did not. Hence there is not a line of 20 lb heart TB's racing today. His X bearing offspring seem to have Princequillo size hearts.

3. He got a dose of something that created lots and lots of fast twitch muscle. My guess is that he got it from the Bold Ruler side of the pedigree.

Having the X linked heart size does a whole lot to explain some of the more random patterns of TB breeding.

[petersd]

If you want to see the new poster-child for the x-factor stallion, look at Moscow Ballet. Compare the number of female SW's to his male ones. And the fact that he's starting to hit as a broodmare sire is another dead giveaway.

[jagger]

Checking the last 18 Broodmare sires of the year reveals 8 from double copy mares, 5 from single copy mares and only three from mares with no x-factor status. The truly great ones, Halo, Seattle Slew, Mr. Prospector, Storm Cat, Danehill, Sadler's Wells and Alydar are all out of double copy mares.

[madelyn]

Oh! Finally a mention of Moscow Ballet! I have a lovely, big daughter of his... and a gorgeous big filly out of her this year. Her name is Miss Ballet. I have long thought Moscow Ballet was underrated.

[louis finochio]

What you refer to fast muscle twitch is what Tessio called nervous energy.

Nervous energy is created by an outcross mating, as Secretariat was.
Bold Ruler = Phalaris sire line over Somethingroyal, by Princequillo = Prince Rose sire line.

Nervous energy can also be created by using two inbred families top and bottom.

These families are not related and thats what creates the nervous energy.
Secretariat had it all thats why TB that are from an outcross mating or two inbred families not related will produce TB that can accomplish what Secretariat and Barbaro did.

[louis finochio]

Moscow Ballet has the same thick stubby neck and conformation that Secretariat had.

MB has 11 crosses of NP and this is what give MB his stout conformation.

What is MB BMS AEI Peterson ?