Often we want to have a one size fits all cut off.  This does not work with these types of tests.  Elevation changes, time for acclimation, weather conditions, and age all contribute to potentional results and the reliablity of these results.  Garbage in garbage out would also fit well.  Let’s say you have 12 month old bulls, acclimated for 3 weeks at 5000 feet elevation.  The reliability of test results would be quite low, but would still give some information, many bulls would/should be retested.  On the other had if these bulls were 15 months old, acclimated at over or near 6500 for 6 weeks, the results would be quite reliable.

Castle Dale is 5676 feet in elavation, this is an exceptable elevation but not excellent.  If testing bulls here I would strongly suggest an acclimation time of 6 weeks or longer, insure that temperatures are well above freezing at the time of testing and test cattle that are well over 12 months of age.