Which digestive organ is larger in axenic animals than in animals with normal flora?

In axenic animals, which are raised in a germ-free environment without any microbiota, the cecum is often larger compared to animals with normal flora. This enlargement occurs due to the absence of microbial fermentation processes that typically occur in the digestive system of conventionally housed animals.

In animals with a normal gut flora, microorganisms play a crucial role in the breakdown of complex carbohydrates and production of short-chain fatty acids, which contribute to the maintenance of gut health and influence the size of digestive organs. The cecum, being part of the large intestine, is instrumental in fermenting undigested food materials and absorbing water and salts.

In axenic conditions, the body may adapt to the absence of microbial influences by increasing the size of the cecum in an attempt to compensate for the lack of microbial digestion. This anatomical adaptation reflects the digestive needs of these animals, emphasizing the role of the gut microbiome in shaping the morphology and function of the digestive organs in animals raised in standard environments.