What characterizes a ruminant disorder?

A ruminant disorder is primarily characterized by the repeated regurgitation of food, which is a behavior commonly seen in ruminant animals, such as cattle, sheep, and goats. These animals have a specialized stomach structure that allows them to break down complex plant materials through a process of fermentation. The process involves the animal (1) ingesting food, (2) allowing initial fermentation in the rumen, (3) regurgitating it as cud to chew it again for better digestion, and (4) swallowing it for further processing. Thus, the core feature of ruminant behavior is this regurgitation, which is integral to their digestive cycle.

In the context of the given options, the behavior of ingested food excessively is not specific to a ruminant disorder; it can be seen in various animals under different circumstances. Compulsive calorie restriction and fear of gaining weight are more related to eating disorders seen in humans and do not pertain to the digestive and physiological processes of ruminants. Therefore, the essential aspect of a ruminant disorder revolves around the phenomenon of regurgitation, making that the correct identification.