Animal Breeds: The Science and Practice of Selective Breeding
In the world of agriculture and animal husbandry, the concept of a breed is fundamental. While we often use the term casually, a breed refers to a specific group of domestic animals that share a homogeneous appearance, known as a phenotype, as well as consistent behavior and other distinguishing characteristics. These traits separate them from other organisms within the same species.
Interestingly, there is no single, scientifically accepted definition of a breed. Instead, it is often viewed as a "term of art" used by breeders who reach a consensus on which qualities define a specific subset of a species. Breeds emerge through genetic isolation, which can be driven by natural adaptation to a specific environment, intentional selective breeding, or a combination of both.
Key Facts
- Breeding True: A requirement for a breed is the ability to produce offspring with the same predictable traits when mated within the group.
- Foundation Stock: The original animals selected from a gene pool to establish the desired characteristics of a new breed.
- Selective Breeding: The process of mating the most desirable representatives of a group to pass specific traits to their progeny.
- Cultivars: The term used for plant breeds.
- Native Breeds: Breeds that originate within a specific country or nation.
The Process of Establishing a Breed
The creation of a breed begins with a breeder or a group of breeders who identify a specific goal or "breed model." They start by selecting foundation stock—individuals from a gene pool that possess the necessary qualities to achieve that model. Through selective breeding, these desirable traits are concentrated and passed down to future generations.
To maintain consistency, breeders often refer to a breed standard. This is a written description that outlines the desirable and undesirable characteristics of the breed, serving as a blueprint for future selection.
![Braunvieh, a dairy breed[1] with high milk production and little milk fat](/images/32/b7/32b74ff1608c46f365ae25352d407be2459f4651b97ffdc72921f8528fe8169c.jpg)
Maintaining Breed Characteristics
Breed traits are inherited, meaning purebred animals pass these genetic characteristics from one generation to the next. To preserve the integrity of a breed, breeders select animals that best exemplify the desired traits while avoiding those with faults or genetic defects.
A healthy breed population must be large enough to maintain these specified parameters without relying on forced inbreeding, which can lead to genetic complications.
Crossbreeds vs. Hybrids
When animals of two different breeds are mated, the resulting offspring are called crossbreeds or mixed breeds. However, if the mating occurs between variants above the breed or cultivar level—such as different species, subspecies, or even different genera—the result is known as a hybrid.
Summary of Breeding Terminology
| Term | Definition | Application |
|---|---|---|
| Breed | Homogeneous group within a species that breeds true | Animals |
| Cultivar | A cultivated variety of a plant | Plants |
| Crossbreed | Offspring of two different breeds | Animals |
| Hybrid | Offspring of different species or genera | Animals and Plants |
Commonly Categorized Breeds
Breeds are documented across a wide variety of domestic species to preserve biodiversity and agricultural utility:
- Mammals: Including cattle, dogs, cats, horses, sheep, goats, pigs, donkeys, rabbits, and various rat and guinea pig strains.
- Birds: Including chickens, ducks, geese, pigeons, and turkeys.
- Insects: Specifically subspecies of Apis mellifera (honey bees).
Frequently Asked Questions
What does it mean for a breed to "breed true"?
Breeding true occurs when individuals of the same breed are mated and consistently produce offspring that exhibit the same predictable physical and behavioral traits as the parents.
What is the difference between a crossbreed and a hybrid?
A crossbreed is the result of mating two different breeds within the same species. A hybrid is the result of mating organisms from different species, subspecies, or genera.
What is a breed standard?
A breed standard is a formal, written document that describes the ideal characteristics of a breed, helping breeders identify desirable traits and avoid faults.
How are breeds different from species?
A species is a biological classification, whereas a breed is a subset of a species created through genetic isolation and selective breeding. Breeds are not always biologically verifiable classifications but are often based on breeder consensus.
What is foundation stock?
Foundation stock refers to the initial group of animals selected from a general population to start a new breed because they possess the specific traits the breeder wishes to enhance.