How many sperm straws come from a bulls semen?

There can be over a billion sperm in one 0.25 ml straw of bull semen.

As many as what a breeder needs. Bulls don't produce semen that need to be collected like with cows that produce milk. A bull can fill thousands of straws per year if need be, depending on the demand...

if semen comes out and no sperm that means you are not yet processed and not making sperm yet

There are at least 6 to10 million sperm per ejaculation.

yes