They received medical care by their owners. We know it because Roman doctors couldn't ask for the same pay for curing a slave as for curing a free person. Slaves were quite expensive, so their owners would want them healthy and working. read more
Plutarch, writing at the end of the 1st century AD, when slaves received better treatment, complained of the cruelty of Cato the Elder (who lived 300 years earlier than him), selling his slaves the moment they got old or sick. read more