What is a defining aspect of the "strain" of rabbits in terms of breeding?

The defining aspect of a "strain" of rabbits in terms of breeding is a race or stock with marked racial characteristics. This means that a strain represents a group of rabbits that have distinct, consistent traits that distinguish them from other groups. These characteristics can include specific physical features, coat types, patterns, and even behavioral attributes that are preserved through selective breeding. The emphasis on maintaining these defining traits helps ensure that rabbits within a strain exhibit a certain level of uniformity, which is crucial for breeding purposes and for meeting breed standards.

Other aspects like size and weight, general coloration, or lack of distinguishing features do not accurately reflect the fundamental concept of a strain, as they either refer to physical attributes that can vary widely or imply an absence of defined traits, which contradicts the purpose of establishing a specific strain.