JTM said:
There is the theory that carrier cattle are better, more bone, stouter hips, and more thickness. So if this is true, which I hear is, but don't know from experience, then along with breeding to carriers you will more than likely have stouter calves when the calves are carriers. Now add to that the genetics of the carriers to begin with are mostly high birthweight, big boned, etc. I think it's safe to say that the calves will be bigger and stouter and you are taking more of a risk in breeding to that type. They have been specifically selected for certain traits, low birthweight and calving ease aren't among them.
I think you hit the nail on the head in this statement. I know many will argue with me, and will tell me I am an idiot and do not know how anything works when I say this. But I have a college education in this type of thing so I am still fairly confident in my stance on it, at the same time I dont claim to be an expert, so I am sure there are experts who could explain it better. But from my understanding of genetics and how they work. TH is a mutant gene that affects the tibial development(or the legs if you need laymens terms) and doesnt affect any other part of the body...PHA is a mutant gene affecting the development of the lungs and not any other part of the body. Both genes are completely recessive, tere is no known codominance in these genes. Which means if the calf is not omozygous for te gene, then it affects absolutely nothing in the calf, and if it is omosygous then it is lethal. So if they are carriers then the gene influences development in no way. Many will say there is a direct tie between these genes and amount of bone, stoutness, amount and quality of hair, etc. The gene doesnt cause this though as many will argue. The TH/PHA genes dont make one bigger boned, hairrier,etc. The correlation between the 2 is that many of the bloodlines that pass these genes just happened to be the ones that were bigger boned, heavier muscled, harrier etc to begin with. We dont (or shouldnt) breed to these bloodlines wanting these genes. We breed to them wanting the positives such as hair and bone, this mutant gene that often comes along with it is just extra, the muscle, hair and bone dont come because of the gene or visa versa. In my opinion it just goes along with saying, sometimes you have to take the bad with the good. Unlike many others I think it is very possible for animals that are carriers and posses all the positives to pass on the positives without the negative(TH/PHA) and in my opinion I think there are plenty of quality double clean specimens out there out of carrier parents to support that. The reason we see so man carrier cattle out there winning is one there are a lot of good carriers out there, and many people are breeding these good carriers to other good carriers, doubling the chances that they will produce a carrier, and doubling chances they will have a lethal calf, and possibly loose the cow in the process.
There are many breeders out there that absolutely will not use a carrier in breeding, because they feel it is immoral to allow the gene to continue. Then there are those like me, while I feel we should try to eradicate as many genetic deffects as possible, I dont always feel it is immoral if you allow the gene to pass on. Many of those breeders, such as myself, will use a carrier but will not breed carrier to carrier. We dont do it so much because of our moral feelings, we do it because we are smaller breeders, and want to avaid the loss of a lethal calf, and cant afford the gamble of possibly loosing a good cow in the process. Regardless of the reason however, I think as more people become concious of these deffects, and many breeds require you to test and report the carrier status(some even go as far as to decline registration to animals that are carriers of defects) I think you will see more and more good CLEAN cattle. Do I think it will ever truly disappear, no, but I do think you will see more clean cattle that are competitive with the carriers.
In regards to the original posts, I dont know that I see a dwindling number of clean bulls, I think I actually see an increase in quality of clean bulls. But just like the above poster stated, the gene will not directly cause bigger calves (well except in lethal PHA calves, they tend to be huge as a result) but at the same time most of the animals that carry the genes also come from bloodlines known for bigger calves, or biger shouldered calves that dont come as easily.
Please forgive me for the tangent.
