Yes. We had to stop useing him right away. They all PAP high and we lost a couple of calves. Our high seller last year was a Fu and we lucked out. He ended up winning a competitive county fair in CO but I won't use the bull again. To bad cause he worked well for us. By the way I do have a few units of semen left that's for sale.
It's a tough thing we have to deal with up here in the high country. We lose them as babies usually if they have some sort of illness at a young age. Showstopper, no need to worry about Fu at low elevations. Only thing I'd add to the CSU article is the higher the animal is PAP tested the more accurate the test. Tests taken under 6,000 ft elevation are not near as accurate as those taken over that. For anyone looking for true high altitude cattle PM me I've got a pile for sale this November. Neighbor who I work closely with is having a large bred female sale.
I guess the better question is how does it effect ai calves if your at altitude? We are around 5000 feet and have never had problems with it but don't want to ai to a bull and have problems with the calves. Does it matter how the bull tests if the cows are bred and calved at altitude.
I know of two instances of calves calved in Wyoming at 5100 ft above sea level. One stayed in Wyoming and died before the county fair and the other went to Colorado (also died). The dams as far as I know never had calves out of other bulls that had problems.
We have a Fu cow that we just weaned her second calf off of no issues, we live at 7000 feet and or cows run up to 10,000. She raised a hell of a heifer out of Dakota Gold. The cow is PB Hereford on the bottom side.