Kentucky Derby and Preakness-winning trainer Doug O'Neill on Wednesday dropped his appeal of a 45-day suspension stemming from an excess of carbon dioxide in one of his horses in 2010. He will serve the penalty starting Aug. 19.

O'Neill said the suspension was reduced to 40 days, and California Horse Racing Board spokesman Mike Marten confirmed it.

The punishment runs until Sept. 27, which means O'Neill will miss the final 2½ weeks of the Del Mar meet that ends Sept. 5. California's three major tracks then take a two-week break before racing resumes at Santa Anita on Sept. 28. During his suspension, O'Neill's barn and horses will be supervised by assistant Leandro Mora.

O'Neill originally said he would appeal the suspension because he questioned the test findings that showed excessive carbon dioxide. The 40-day punishment is contingent upon him not having any Class 1, 2 or 3 drug violations within 18 months in any jurisdiction. He still must pay a $15,000 fine.

"I just felt my time and money could be better spent doing more positive stuff," he told The Associated Press by phone. "I'm looking forward to getting it behind me. It will give me a chance to kind of pause a little bit, do things better, be more organized and give back to an industry that I absolutely love."

O'Neill said he has no specific plans for his imposed time off, adding that "I hope to learn some new things."

He is the fifth-leading trainer in earnings nationally with $4,484,080 so far this year and wins at an 18 percent clip.

O'Neill was originally given a 180-day suspension by the California board. A hearing officer found that the carbon dioxide level was not caused by milkshaking, an illegal practice which involves giving a horse a mixture of bicarbonate substances to stave off fatigue. However, the officer said O'Neill should be suspended under the trainer responsibility rule.

"I respect the racing board," O'Neill said, while adding that he doesn't agree with the board.

He saddled I'll Have Another to victories in the Derby and Preakness. The colt was suddenly retired with a tendon injury the day before the June 9 Belmont Stakes, which prevented him from trying to become racing's first Triple Crown winner in 34 years.