A hit US television series starring Dustin Hoffman has been canceled after three horses died during filming, the channel which makes the show announced Wednesday. \"Luck,\" about thoroughbred racing and also starring Nick Nolte, launched in January and had already been picked up for a second season, with production mostly at a horsetrack east of Los Angeles. But a first horse died on the set in 2010 and another died last year. Then a third animal had to be put down on Tuesday after falling backwards and striking its head, despite new safety rules put in place. \"Safety is always of paramount concern,\" said Home Box Office, which aired the show. \"We maintained the highest safety standards .. higher in fact than any protocols existing in horse racing anywhere with many fewer incidents than occur in racing or than befall horses normally in barns at night or pastures. \"While we maintained the highest safety standards possible, accidents unfortunately happen and it is impossible to guarantee they won\'t in the future. Accordingly, we have reached this difficult decision,\" it said. Executive producers David Milch and Michael Mann added: \"The two of us loved this series, loved the cast, crew and writers. This has been a tremendous collaboration and one that we plan to continue in the future.\"