Cayley, a six-year-old-Labrador Retriever, is given drops of a cannabis based tincture to treat hip pain and anxiety

Pet owners in the US are turning to medical marijuana in growing numbers to treat their sickly pets for ailments ranging from arthritis to cancer.

Dogs, cats, pigs, horses, lizards and even turtles are among animals said to have benefited from the drug, which has become a multi-billion dollar industry since its legalisation for human medical use in 29 American states.

“We are seeing about 20 per cent growth every month; we are treating thousands of animals,” said Alison Ettel, founder of a California company that supplies pet cannabis products.

The US Food and Drug Administration, the federal agency that oversees the safety, efficacy and security of human and veterinary drugs, has not approved marijuana for use either in humans or animals despite individual states