McLean Robertson, a Midwestern trainer who has annually topped $2 million in earnings for the past decade, has been issued a provisional suspension after a gelding he trained tested positive for altrenogest, an estrogen suppressant that is banned for use in geldings under the rules being enforced by the Horseracing Integrity and Welfare Unit. Johnny Up, a 5-year-old gelding, tested positive for altrenogest after winning a claiming race at Canterbury Park in Shakopee, Minnesota, on June 4, according to a notice posted on HIWU’s website. Although altrenogest – which is more popularly known by one of its brand names, such as Regumate -- can be used on a prescription basis in non-spayed females, it is banned for all other horses. The recommended penalty for banned substances under the HIWU rules that went into effect on May 22 is a two-year suspension, though the penalty can be reduced significantly based on several factors. A positive for a banned substance, even prior to a split sample being returned, calls for the trainer and horse to be provisionally suspended while the matter is adjudicated. Robertson declined to comment on Wednesday. Robertson is the fifth trainer to be issued a provisional suspension under the new HIWU rules since May 22. A veterinarian has also been issued a provisional suspension. Altrenogest is routinely used in mares in Thoroughbred racing to suppress estrus, which can complicate barn management. According to records in a national database of rulings, Robertson has had a relatively clean record over his nearly 20-year training career, with the exception of a 90-day suspension issued in 2015 in Minnesota after a horse he trained tested positive for methamphetamine, a Class 1 drug. In his career, Robertson has trained 1,544 winners from 7,108 starters, for a strike rate of 22 percent. This year, he has won 30 races from 146 starts. :: Want to learn more about handicapping and wagering? Check out DRF's Handicapping 101 and Wagering 101 pages.