DEL MAR, Calif. - A day after two horses were euthanized as a result of injuries suffered during training, and amidst complaints from trainers about the firmness of the track, Del Mar altered the maintenance procedure of its synthetic main track Friday.\nFriday's maintenance, which took place after training hours, may be the first of two such projects within a week. A second more extensive maintenance may occur after training hours Monday, depending on how the surface reacts over the weekend, according to director of racing Tom Robbins.\nTrack workers on Friday harrowed the Polytrack synthetic surface to a depth of 3 1/2 to 4 inches with a "cultivator" machine that is designed to "loosen the material and get some air down there," Robbins said.\nA similar renovation has been done after training on recent Mondays, a dark day, Robbins said.\nThursday, Sovine, a high-priced claimer, and the maiden Pauper's Prize were euthanized as a result of injuries suffered during training. Sovine suffered a pastern injury. Pauper's Prize injured a shoulder.\nSince the track opened for training in mid-July prior to the July 22 start of the meeting, 10 horses have been euthanized because of injuries during racing and training. There have been four horses euthanized as a result of injuries during racing, three on the main track and one on turf, and six during training hours.\nDuring the 2008 meeting, 10 horses were euthanized as a result of injuries suffered in racing or training. The current meeting runs through Sept. 9.\nThe number of horses euthanized at the meeting has been a sensitive issue for track management, Robbins said.\n"We want to have a good record," Robbins said. "It's the highest priority."\nTrainers also have reported a rash of lesser injuries as minor as bruised feet that result in a few days of missed training or as severe as suspensory or tibia injuries that result in several months off or the end of a horse's racing career.\n"There is more and more grumbling," said Ed Halpern, executive director of the California Thoroughbred Trainers Association.\nTrainer Mike Puype said minor injuries have sidelined some of his horses.\n"The track has been hard on feet," Puype said. "When the track is good, I love training on it, but I think they have some serious maintenance issues they haven't been able to figure out."\nJeff Mullins said he had a horse euthanized on the Polytrack surface in 2007 but otherwise had no injuries during that season. Most of the injuries to his stable this year have been during training hours.\n"I wish they could get a consistent program down and keep it that way," he said.\nThere have been some complaints to track foreman Steve Wood about the firmness of the surface, but Robbins said he has not been approached on the subject.\n"Steve said he had a couple of guys talk to him," Robbins said.\nRobbins said the track was reluctant to use the most extensive renovation procedure, harrowing to a depth of five inches in a procedure known as power-harrowing, to avoid a disruption in the way the track performs. The track underwent such a renovation on July 27, leading to a slower and more tiring surface for horses during races on July 29-30.\nRobbins said daily training from approximately 2,200 horses based at the track causes the track to "go through some changes."\n"We haven't power-harrowed for three weeks, and that decision will be made over the weekend," he said. "It's been pretty consistent. We don't want to see dramatic changes from day to day."