Like okotoks, we used a few TH carrier bulls before the defect was known about. I think we had some of the first TH defect calves around after we used a low birthweight grand son of Deerpark Improver on a set of Improver 57th grand daughters. Out of the first 10 heifers to calve, we had 6 TH calves. ( We were baffled at what was causing this, as were our vets). We were very suspicous of it being environmental in nature, as we had air monitors in all our pastures at the time. These were placed there by oil companies who were a part of a 5 year study on the affects of the oil industry on beef production. These calves were all born at the front end of the calving season so we were not sure what to expect from the rest of the herd. ( we had 5 of these TH calves born in 2 days!!) It was just weeks after these calves were born, that I read the first article on TH, in Shorthorn Country. I phoned Roger Hunsley, and I described what our calves looked like, and he said I had described the classic signs of TH. As the defect was just being researched, he would not say what line was propogating the defect and he wanted me to send information of th pedigrees of the sire and dams. Improver was the only common denominator, so I was suspicious but did not know for sure until this information was released several months later. The sire was an excellent bull but he was shipped to slaughter immediately and I made sure an unrelated bull was used on these females that year.
We tested our entire herd once the test was available and we found we had several carriers. Some were what we considered our best breeding females. We kept a few of the best ones, and the rest were sent to slaughter. My intention was to keep the better carrier females until we had a THF daughter to replace her. We did that with several of them, and some were kept to be used as recips. I have to say, that I have not seen any differences in milking ability between THF and THC sisters. Some of the THC cows still in our herd may be our best milking females. I have one carrier cow that has now had 3 calves- the first was a natural calf as I do not put embryos in heifers. This calf turned out to be a THF bull and he topped our bull sale 2 years ago at $9000. Her second was an ET calf. In year 3 she did not hold an embryo so she was bred to one of our herd bulls. She again had a TH free bull and he sold for $6800. I'm still waiting for a THF heifer, and she may never have one as she is carrying an embryo now.She may never have another THF calf so despite her excellent production record, she is considered to be in our recip herd. Right now we have 3 THC females in production. They are excellent producers but until they have an ET calf, or produce a THF calf, their offspring will be fed out and slaughtered. That is just my opinion and I have no plans to propogate genetic defects
In regards to the milking ability of clubby cows, I would suspect it has more to do with other genetic reasons than the fact that many come from THC bloodlines. In regards to the Double Vision line, I used a white ET son of his on my black cows for a few years. His donor dam was an extreme heavy milking female, and his daughters were moderate milking females. If they came from a good milking cow, they milked fine,but if they were from a moderate milking female they were marginal at best. I also have had a few X Ray Vision daughters from a flush, and they also milked well, but the donor dam was also a very good milking female. That is my limited experience using the Vision lines. I also have had a few Ar Su Lu Kool daughters, and was very fortunate in every one of them being THF and PHAF. They all had excellent udders and milked very well.
We had several half sisters from two different THC bulls and the TH carriers were very good milking cows as were the THF sisters. In our case THC didn't seem to influence milking ability.
