A move to create new rules to prevent racehorses in Illinois from being sold for slaughter was voted down and tabled until at least next month during a meeting of the Illinois Racing Board on Tuesday, prompting Kathy Byrne, the commissioner who has pushed for enhanced anti-slaughter regulation and submitted the item on the Tuesday agenda, to withdraw the proposal and hastily leave the meeting, saying she was resigning her post. Byrne, the daughter of former Chicago Mayor Jane Byrne, was appointed to the IRB in 2011 by Gov. Pat Quinn, a Democrat, and along with Roger Whalen was one of the two longest-serving commissioners on the 11-member board. The board includes five commissioners appointed this year by Republican Gov. Bruce Rauner, among them chairman Jeffrey Brincat. The board’s position on the anti-slaughter measure Tuesday was the tipping point for Byrne, who has regularly clashed with Brincat and who on Wednesday confirmed her resignation. “There is no way that I can successfully advocate for this industry and the rights of the various parties in the industry with this current governance,” Byrne said. “I can’t be effective, and if anything, I might be a hindrance: If I say something is white, then they will say it’s black.” Enhanced anti-slaughter rules were first brought up by Byrne during an IRB meeting in August. Byrne attempted to bring forth the measure during the IRB’s September meeting to award racing dates, but Brincat insisted it be put off until October, and when that meeting was canceled, Byrne’s measure to initiate rulemaking was rescheduled for Tuesday. The amended official language under consideration would have required racetracks to monitor horses leaving their grounds to attempt to ensure that they were not on the way, directly or indirectly, to slaughterhouses. Trainers or owners would be required to sign forms attesting to a departing horse’s destination. Both Chicago-area horsemen’s groups, the Illinois Thoroughbred Horsemen’s Association and the Illinois Harness Horsemen’s Association, supported Byrne’s measure, which seemed to be on the way to passage Tuesday when Arlington chairman Dick Duchossois rose to speak against it, expressing concern about racetracks’ legal liability. Duchossois said Arlington needed more time to review the proposal, but Byrne said the specific language called into question had come straight from Arlington during negotiations over the measure. IRB executive director Domenic DiCera said the board “would welcome that item or that topic to resurface in some form.” The board also approved 2016 contracts between racetracks and account-wagering companies, including a controversial agreement between Hawthorne and Xpressbet. That contract was opposed by the Illinois Thoroughbred Horsemen’s Association because it would reduce the fraction of account-wagering bets accruing to purses if handle at Hawthorne falls below a certain threshold. Horsemen’s groups have the right to veto such contracts, but the board also can override that opposition if it believes the horsemen are acting unreasonably, which it did Tuesday. Finally, the IRB’s medication committee announced that Illinois, catching up to most North American racing jurisdictions, would begin postrace testing for cobalt beginning Dec. 1.