The Texas Racing Commission says attendance is down more than 50 percent and the total wagered on dog races is down 61 percent since 2007.
The industry has seen such a decline that there is only one dog race track still operating in Texas, the Gulf Greyhound Track in La Marque.
State lawmakers have been tossing around the idea of allowing slot machines at racing tracks to boost business, but that legislation doesn't appear to be gaining traction.
Ann Church is the vice president for state affairs at the ASPCA. She says there were more than 1,500 Greyhound injuries at Texas tracks from 2008 through 2011.
"We only look at the actual injuries that are reported officially, we don't make up the numbers, we don't surmise the numbers. So according to Texas officials, these are the number of injuries that have come out. And we do think it's a high number."
The most common injuries were broken legs, dislocations and other broken bones. Church says dogs are also fed substandard meat and are kept in cramped kennels.
Church says the ASPCA opposes allowing slot machines, poker or other forms of gambling to operate at race tracks.
"There's no reason why slot machines should keep the dogs racing. If dog racing doesn't support itself, why prop it up? Let it just end. The dogs are suffering, they don't need to be. Let the sport go."
Of the 22 race tracks still in the U.S., more than half are in Florida, where other forms of gambling are permitted.