“I , like most breeders in Holstein prefer to line breed to the TB blood rather than use it outright.”
This is really going to be the question over the next couple of decades. If I had a lot of skin in the game (money in the stock) I’d likely do the same, but from an observational standpoint I think it’s an interesting question as to how this will go and what the long v. short term aspects will be.
What happened when tbs were brought in originally is that you saw from very quick, very positive results. Some of those results, like with Cottage Son and Corde, created some aspects and effects that lasted through a few generations - especially as line breeding was taking place. Some, like the Ladykiller lines (imo) required more repeated infusions of tb to keep some of the positive effects.
But most of the really nice examples out there, now, in their 4th/5th generations, show xx or ox infusions on almost ever cross/pedigree tier. In essence, they are very much examples of a situation where F1s were bred to each other on a very widespread pattern in the 3rd/4th generation. Offspring have then been line bred over the next 3 or so generations and the concentrations have worked pretty well.
So now that there have been 2-3 generations of good type and performance maintained without infusion of a lot of new tb blood and based on line breeding of the older xx (and ox) blood the question is what will hold in the genetics? It’s one thing for infusions of athleticism to hold over 4 or so generations of linebreeding. The question is then going to become whether or not that linebreeding effort has so successfully concentrated the traits for which the infusions were sought that the pool is self sustaining now, or if, as the generational tier from which the original base became so broadly an F1 base, with many F2 bred to each other, drifts back to the 6th, 7th, etc. tier rather than the 3rd/4thish tier, whether even with line breeding of the originally successful xx oand ox infusions the traits of the original base will begin to resurface.
In different breeding pools and aspects, I’ve seen both things happen so I think it will be interesting. Once upon the time, the “insight” was that if you didn’t keep reinfusing blood, they went back to bigger/heavier fairly quickly but that was observational from some registries that did not and do not have the linebreeding on xx that Holstein has - that line breeding has created a concentration of certain genetics that may end up being self sustaining. It has been self-sustaining in the last few generations.
And even if it is not as self sustaining, another issue will become to what extent overall catty athleticism is going to be needed, over raw scope, in the courses of the future. And to what extent the tb breeding preserves the overall athleticism. Observationally - I’d place a long term bet on the need for more direct tb reinfusions being needed by the time the originally sucessful blood infusions get back beyond the 7th or so generation, even with the strong consolidations that have been derived from linebreeding. OTOH, if it was my skin in the game, I’d have a hell of a time doing anything much different with my nice mares in this generation than what has been done in the preceding couple of generations so successfully, i.e., look for the best linebreeding options consistent with my mare’s needs that are available.
I think the winning strategy for the short term is repeititon of what has been successful for the last 2 or 3 generations, but the winning strategy for the long term hasn’t been written yet. What I do see as a good thing is that eventers have been coming back around to the concept that a good xx or F1 suits most of them, and their sport, best - even with the changes to accomodate the wbs. I think this is a good thing bc over a couple of generations, it is likely to result in some preservation of some focus on sirelines that are 1/2 or more xx and that have exceptional athleticism. If the linebreeding consolidation efforts (not just in Holstein, but maybe most prominently there) are successful in being self sustaining, it won’t be an issue. But if not, with non-sprint tbs getting a bit sparser, it is nice to think that there may be an area of sport that preserves some of that athleticism if it is needed by the time you are looking at the Corde’s and Cottage Sons being 8th tier and further back, instead of front pagers.
Personally, I believe there are a lot of wonderful tbs here in the US that never hit the radar and that could be an incredible boon to our domestic breeding programs. That’s not quite the same as saying, though, that I think the best short term bet for Jumper breeder is to use direct tb infusions, but I do worry a bit about what happens long term if they don’t. fwiw.
