PHOENIX — A herd of wild horses living near Arizona’s Salt River will get enhanced protection under a new agreement between state and federal agencies.

The Arizona attorney general’s office officially approved a partnership Thursday between the state Department of Agriculture and the U.S. Forest Service. It fully enacts legislation signed by Gov. Doug Ducey last year making it illegal to harass, shoot, kill or slaughter a horse that is part of the herd.

It is the result of negotiations between lawmakers, state and federal officials, and advocacy groups such as the Salt River Wild Horse Management Group.

Under the agreement, the Forest Service will construct fences around an area designated for the horses to prevent them from mingling with other livestock. The agency also will facilitate a proposed management plan and issue any authorizations the state needs for approved activities and facilities on federal land. It also must reimburse the state for expenses that do not exceed $90,750 in the next fiscal year.

The Arizona Department of Agriculture, meanwhile, will be expected collaborate on the plan and hire a Salt River horse “liaison” to work with the Forest Service and help choose any third-party contractors. The contractors would help with responsibilities such as administering equine birth control and monitoring veterinary treatment.

State Rep. Kelly Townsend, who sponsored the legislation, said Friday that the agreement marks the end of what has been a complicated and arduous process.

“Arizonans and visitors as far away as Europe come to enjoy these beautiful creatures, and now we can rest assured that we can continue to go and observe their innocence and wild existence in our own backyard,” the Mesa Republican said in a statement.

About 100 horses are in the herd that has historically lived around the lower Salt River and Saguaro Lake east of Phoenix. Arizona records indicate the herd has lived in the same area since about 1890, making them unique among other herds across the country.

The proposal was developed after a Forest Service plan to remove them sparked an outcry from groups like the Salt River Wild Horse Management Group. The organization said Friday that its volunteers are willing to provide third-party assistance for the state.