Rasmussen Factor

[LB]

There's an interesting article on the BloodHorse site about Rachel Alexandra's pedigree which shows a very high incidence of Rasmussen influences.

For those of us who like to think that mares in a pedigree deserve some credit too the article can be found here:


http://cs.bloodhorse.com/blogs/scot/arc ... actor.aspx

[Tappiano]

If it weren't for mares we would not have any large hearts being passed down

[griff]

If it were not for mares we would also not have any small hearts either.. ASctually if it were not for mares we would not have anything passed down

griff

[foothillsequine]

Can someone please help me in understanding this factor? I think I get it, but then, after reading, I seem to be more confused.

[xfactor fan]

The basic idea is that by inbreeding to mares rather than stallions you concentrate genetic qualities that make successful racehorses.

From the genetic standpoint this could mean inbreeding to the same type of mtDNA, to the X chromosome, or to genes that are on regular chromosomes but are only expressed when transmitted via the female line. And yes, the idea that chromosomes and genes know and care about which side of the family they came from was hard to wrap my brain around.

I've seen some statistical work to indicate that the RF factor doesn't exist. In fact if you google the term a bunch of info will show up, both pro and con.

Somethingroyal is one of the mares that is usually included as a significant mare, but when inbreeding to her, do you get the genes that produced Secretariat, or the ones that produced The Bride?

[foothillsequine]

Thanks xfactor, I think that helps. But, if it is statistically unreliable, why is it still practiced? Or is it?

[ASB]

I believe in it.

I think as we learn more about genetics, we're starting to see that the female lines may bring more to the table and if you're inbreeding to the significant female lines in a pedigree, it can only increase your chances of getting the "right" genes to produce a superior runner, or in some cases, a superior producer.

[foothillsequine]

Okay, I get that. If you are inbreeding to bring out significant factors from a mare, how close is the inbreeding? Are you only inbreeding the females? By that I mean, would you breed a brother to a sister for example? (to me, that seems kind of close), or how is this done? How do you determine success in this breeding methodology? Dang it, now it seems that I just have more questsions!

[ASB]

By definition, it's inbreeding within 5 generations.

And in my opinion, inbreeding to other's in the pedigree of quality besides the female in question, just reenforces focused breeding. It doesn't have to be exclusively the female.

[foothillsequine]

Thanks ASB, that makes more sense. I appreciate your help and patience!

[hpkingjr]

Old article on the RF factor for background information.

http://www.equicross.com/Inbreeding_to_ ... _Lines.htm

[foothillsequine]

Thank you! Very interesting article, I appreciate it.

[griff]

There are two Not For Love yearlings in the October F-T sale that are 3S x 3D to Numbered Account

griff

[merse]

First off, let me state that Rasmussen Factors are always considered in my breeding decisions but only as one of many factors and mainly in the case of a tie-breaker (i.e. with all other factors approximately equal and one possible mating has a RF and the other doesn't, I'll opt for the one that offers the RF).

I have read a ton of stuff on the pros and cons of the RF and believe, like a lot of the theories in breeding, that there is simply not a sufficient statistical sample size to really nail it down. That doesn't mean it might not be true however, it just means one has to intelligently analyze the data input.

The thing a lot of people forget is that the RF principle talks about inbreeding to superior females and herein lies the rub. If you have two horses with the RF, that RF may be The Bride (Secretariat's full sister - see earlier comment in this thread) for Horse A or it may be to Personal Ensign (a superior runner and producer) for Horse B. For statistical purposes, both horses have the RF. I personally feel, the RF in Horse B will get you a better runner.

I also believe that geographical limitations play a big part in the older pedigrees with the RF. Before the recent, "modern area" people pretty much remained local for their breeding purposes and stallion books were smaller and more closely selected in terms of what mares were allowed "in." Now, one often may ship a mare out of state to breed to a stallion.

Take for example a farm like Claiborne. I use them as an example because I like looking at their mares in sales catalogs because you typically will see the Claiborne stallion roster as one goes down the tail female line (Mare A is by Seeking the Gold out of a Danzig daughter who is out of an Unbridled daughter who is out of a Buckpasser daughter who is out of a Round Table daughter, etc.). In a mare's broodmare career, assume her colt/filly produce is 50%/50%. Breeding from a somewhat "closed" broodmare band, it would stand to reason that, somewhere down the line, a mare's descendent will probably be bred to a Claiborne stallion who has the same female ancestor - thus creating a Rasmussen Factor.

[Shammy Davis]

I know this is a little off the subject but I was following a copy of Breeding to SF by Faversham & Rasmussen on Abebooks. The copy sold for $600.00 I've only read a few commentaries on the theory, but for that price I'd expect major accomplishments in my breeding program.