This is part of our series on new California laws taking effect in 2018.
In California, ranchers already need a veterinarian's prescription for certain antibiotic treatments for livestock.
But a new law taking effect in January will require a prescription for all medically important antibiotics used to treat health problems in cattle, sheep and other livestock.
University of California Agricultural Natural Resources farm advisor Dan Macon works with ranchers on livestock production in the northern Sacramento Valley and the Sierra foothills.
Macon notes the law doesn't require a vet to be on site for each animal that needs treatment. But there will need to be a veterinary-client-patient relationship.
As Macon explains, that means "the vet knows the operation, knows the rancher and has some idea of the types of animals and types of issues the rancher may be dealing with.
"And so, it does require some semi-annual check in with the vet at the ranch," he adds.
Macon points out that food animal veterinarians have become increasingly rare.
"People going to vet school today are largely interested in the more profitable lines of work with pets or companion animals," he says.
Macon notes the new law could pose a challenge for California livestock managers and ranchers in places where vets are few and far between.
The law defines livestock as "all animals and poultry, including aquatic and amphibian species, that are raised, kept, or used for profit."
The law does not apply to bees or dogs, cats and pet birds.