RENO — The state of Nevada has signed a cooperative agreement with wild horse protection advocates allowing longtime critics of mustang roundups to have the first chance at purchasing state-captured animals that otherwise might end up at the slaughterhouse. The agreement between Nevada’s Department of Agriculture and California-based Return to Freedom Inc. doesn’t affect the roundup of federally protected horses on mostly U.S. Bureau of Land Management lands in Nevada and much of the West. But it means that in at least three northern Nevada counties, the mustang’s allies won’t have to outbid slaughterhouse buyers at state-sponsored auctions, as they …