There seems to be a direct correlation between hair shedding and fescue toxicity. Living in the heart of fescue country, I tend to agree. The cattle that hold their hair longer tend to take longer to breed back, seem hotter in the summer, and just don't do as well.
The University of Missouri is doing a huge research study trying to link hair shedding to a specific DNA marker. Several months ago they sent out a large announcement that they want producers that have registered stock to sign up and participate to help them with this task. The only commitment needed from me is to take a hair score each year, in May or June, and report it to them, hopefully following the same cows for at least 3 to 4 years. In return, they will run a complete Genome on the cattle enrolled and report it to the registry. A complete genome on a cow is not cheap, and I would love to have my entire herd done for free, so I signed up (this way I know who is hetero black, hetero polled, and many other things). It was pretty simple and painless, and I look forward to getting the data back on my cows. I have a good idea on what cows are susceptible to fescue, and am curious if I am correct in my thinking.
BTW, it is not just simmental cattle that have a problem with shedding. It is in most breeds to a certain extent. I believe they will prove it is a genetic factor, and can be selected against if we can come up with a marker for it (or even EPD). They know that not only does the fescue tend to make them hold their hair, but gains are lower and milk can be suppressed on fescue. It is a wicked thing if the cow can not deal with the toxins, and seems to have a varying degree of tolerance in different cattle. It is not an "all or none" option.
