Breed vs. Strain — What's the Difference?

Breeds are specific groups of domestic animals, such as dogs, cats, or livestock, that have been selectively bred over generations to emphasize certain desirable traits, such as size, temperament, or productivity. These characteristics are relatively stable and recognized across generations, allowing breeds to be officially recognized and classified by various organizations. On the other hand, strains refer to variations within a species, particularly in the context of plants, bacteria, and sometimes inbred animals, which result from a specific genetic makeup. Strains are often identified by their distinct genetic or phenotypic characteristics, which can include resistance to diseases, yield, or specific physical traits.

While breeds are a concept primarily associated with domesticated animals and are a result of selective breeding practices aimed at enhancing certain traits, strains are used more broadly in biology to describe genetic variations within any species, including microorganisms, plants, and animals. Strains are especially important in scientific research and agriculture, where specific genetic variations can lead to significant differences in behavior, disease resistance, or productivity.

The identification and classification of breeds are often governed by breed registries and organizations that set standards for what defines a specific breed. These standards include physical appearance, behavior, and sometimes genetic markers. Conversely, strains do not have formal registries; their identification often depends on the context of use, such as laboratory research, agriculture, or horticulture, where the focus is on the genetic attributes and performance of the strain rather than on meeting a specific breed standard.

Breeds are more about maintaining and refining established traits over generations through controlled breeding practices. This is common in pets and livestock where specific breeds are known for their distinct appearances and behaviors. Strains, however, often arise from both natural genetic variations and targeted breeding or genetic modification to achieve specific outcomes, such as increased resistance to pests or diseases in crops, or specific colors or effects in cannabis plants.

Finally, while the concept of a breed is rooted in tradition and often associated with heritage and culture, strains are a more fluid concept, reflecting ongoing changes and discoveries in genetics and biology. Breeds tell a story of human-animal relationships, selective breeding, and cultural preferences, while strains highlight the dynamic nature of genetics and the potential for adaptation and improvement within all species.