KEITHVILLE, Louisiana—It's a few minutes before 8 a.m. at Chimp Haven, a sanctuary for retired research chimpanzees, and the air fills with their excited hoots and cries. Chimps in an open-air forested enclosure have spotted veterinarian Raven Jackson carrying a caddy packed with their morning's juice treats and frozen bananas. A half-dozen dark-haired chimpanzees crowd the wire metal gate and wait for her to dispense the goodies.

"Hello, Sara Soda," Jackson says to one very large and well-padded female, who opens her mouth wide to swig her juice. "And Rita, you're next," the vet says to the chimpanzee sidled tight against Sara.

Each bottle is filled with a mix of juice and individually tailored vitamins and medicines for the ailments these