20-day-old kittens are usually not fully developed enough to poop on their own. In a natural environment, the defecation of kittens is usually stimulated by the mother cat by licking the kitten's anus. However, if kittens are adopted by humans, their bowel movements may need to be artificially stimulated in the early stages, such as using a moist cotton ball or paper towel to gently massage their anus.

As kittens grow, they will gradually learn how to control their defecation and eventually be able to Defecate spontaneously without external stimulation. This process usually occurs when kittens are about a month old. Therefore, if you are caring for a 20-day-old kitten, you may need to continue artificial bowel stimulation until they are able to resolve the problem on their own.