Trainer Doug O&rsquo;Neill has filed a lawsuit against the California Horse Racing Board alleging that the board is not using the latest available scientific research when enforcing rules on excessive total carbon dioxide in the blood, the signature of an illegal practice known commonly as milkshaking, according to a Los Angeles newspaper.\r\nThe suit claims that the board has ignored scientific studies that have established that &ldquo;the average TCO2 level of normal horses is considerably higher than the level on the basis of which the [racing board] established its testing program,&rdquo; according to L.A. Weekly. In the suit, O&rsquo;Neill has asked the California Circuit Court to shut down the state&rsquo;s TCO2 testing program and prohibit the board from enforcing penalties against him based on a TCO2 violation last year at Del Mar, the newspaper said.\r\nEfforts to obtain the lawsuit early on Thursday were unsuccessful.\r\nDr. Rick Arthur, the CHRB&rsquo;s equine medical director who devised the TCO2 testing program, said that he could not comment on the specifics of the suit but said that the board &ldquo;is looking forward to litigating it.&rdquo;\r\n&ldquo;This is all part of the legal maneuvering in a hearing process in what will likely result in a substantial penalty for a leading trainer,&rdquo; Arthur said.\r\nFour horses trained by O&rsquo;Neill have been found to have excessive TCO2 levels. The most recent incident occurred on Aug. 25, 2010, when his horse Argenta tested positive for an excessive level of TCO2 prior to finishing eighth.\r\nA hearing has yet to be held on the Argenta positive, but O&rsquo;Neill is facing a minimum 30-day penalty for the infraction. In 2010, O&rsquo;Neill served a 15-day suspension handed down by Illinois regulators after his horse Stephen Got Hope tested for an excessive level of TCO2 at the Illinois Derby at Hawthorne.