On another call <a href="http://www.formbysurveys.com/prohealthmemorialhealthcom-74c8.pdf#opened">menshealthscreening.co.uk</a>  Mickelson said the company does not know the cause of the problem. However, he said, independent veterinarians and animal welfare experts have told Tyson officials that Zilmax could be to blame. He declined to elaborate.