So I am the guy that did a search for th and pha read the thread most of it anyway, and had to respond because I could not help myself......
First, as evidenced by having to do a search to find out what th and pha i have not been in the "clubby" side of the beef industry for a long time. But I did do fairly well showing calves out of our herd years ago and now have two kids, four and six years away from showing calves so I thought we would ai a handful of our good limi cross heifers and cows to something that would produce some style in a handful of cows for my kids to get club calves out of. So yes, in some cases clubby side and commercial side do mix.
Second, as evidenced by the fact I took the time to do a search, I try to research what I am getting into. But as mentioned, most commercial cattlemen would likely have no idea what th and pha are. How many of the club calf washout heifers end up Ina salebarn? At some point possibly changing hands a couple times. While they are washouts in the club calf world, what is the odds that a commercial guy buys her for a replacement? It would not be a stretch to assume that there are more then a few carrier cows running in commercial herds, and likewise not much of a stretch that there are some carrier bulls that get kept and sold to commercial cattlemen, or perhaps kept out of a carrier heifer that had a poppin good bull calf. All of this can happen and does happen.
I am not saying this to bash people that breed carriers. We have a defects called EIC and CNM in the competitive side of the labrador retriever world. Carriers are bred routinely, though the same controversy as to wether or not to breed carriers exists there as well. I would say though the one difference is in the world of competitive dogs a breeder may have ten females and have an enormous amount of time invested in each dog and be intimately aware of carrier status, but also make sure that if they do breed and produce carriers the buyers are aware that they have an animal that may be a carrier. As many times as cattle can change hands, as many cows as most commercial guys have etc I doubt that when carrier heifers are sold to the final destination a fraction of the new owners are aware that they have a POTENTIAL genetic problem that needs to be managed.
With what I am doing, I would avoid using a carrier bull at all costs. Two reason, I do not want to have to worry about it in my herd, but also, because twenty years ago when I was AIing for my own club calves I am almost certain I used some bulls that have been mentioned as possible early carriers. Odds would be low that three generations later one of the two or three heifers we kept out of that would still put a carrier in the heard, I am not going to test every cow in the herd just to make sure......
As for genes being linked, the way meiosis happens, Genes that may not be linked, but are close together on the chain tend to stay together in the crossing over that chromosomes do before they split to form eggs or sperm, can get more tech if desired but it is like cutting cards, the odds of cutting between two cards is low which is the basis of a lot card tricks I know. In humans blonde hair and blue eyes go together a lot, due to the reessive genes being close together and there fore likely to be on the same chunk of DNA at cross over( and perhaps good hairdressers ;-). ). In Labs EIC and a performance enhancing gene making dogs able to see and remember where a bird is thrown are thought to be close on the chain, becaus emany of the really good dogs, from various lines carry the recessive mutation. Likely, the th and pha gene are close on the DNA chain to genes that make calves grow lots of muscle and lots of hair. Nt linked, but close enough together on the chromosome that the. Odds of splitting between the two genes is low........
In closing, if you are breeding Clubbies, by all means have at it. Breed those carriers if they throw the steers that your customers want and that win shows. Shoot someday if one of my kids want a steer and we do not have a good one that year I would buy one. But please please please, keep track of the heifers that may be carriers and do what you can to make sure that people know they are possibly carriers so that the mutation does not make it to the commercial side in the hands of people who don't know about it and can not feasibly manage it.
