I'm going to start charging you guys for insurance advice:
On livestock mortality policies, there are 2 general ways you can go with these. The first, and most common is to go with a company like Harding and Harding, or American Livestock Insurance, that will actually cover the animal for a specified amount. These are the policies that will require a vet exam before the policy is issued, as well as upon verification of death. They are also quite a bit more expensive since they cover the full stated value of 1 animal against the peril of death.
The second common form of livestock insurance is to put them under a farm blanket coverage. Typically you will say that you have 50 cows valued at $50,000, or $1,000 per cow. The problem with this is that the animals are typically only covered upon a listed peril in the policy (fire, wind, hail, aircraft, etc). If you have a group of cattle standing along a fence that gets hit by lightning, you will be covered since lightning is a listed peril on the policy. If the bulls get in a fight and one gets killed, you're out of luck. Some policies do allow for endorsements for stated value items like bulls or show animals, but I would recommend going with a mortality policy since it's more fitting to what you're wanting to cover.
I posted in another thread about checking your farm policy for equipment breakdown coverage. If your semen tank ruptures and the semen is not recoverable, the equipment breakdown coverage should pay you the cash value of the semen. Many of my farm companies also have coverage for reproductive materials. Whether this be semen, embryo's, etc.
Of course, with all of these options, they all come with a price tag. Here is the simplest rule to remember when you look at these: if one option is considerably cheaper, it's probably for a reason. Why do you think it costs $300 to insure a $5,000 bull for 6 months with Harding and Harding, while it costs $300 to insured $50,000 worth of livestock for a year