The Impacts Behind Selective Breeding

Aradhana Anand
Dec 25, 2024
4 min read

Updated: Mar 9, 2025

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What is selective breeding? According to Britannica, “selective breeding is the practice of mating individuals with desired traits as a means of increasing the frequency of those traits in a population.”. In simpler terms, this means that it is when specifically chosen organisms are bred with each other to make offspring have specifically needed/wanted traits. Selective breeding can be done for many reasons, which have positive improvements in agriculture or unintended consequences like recessive genetic diseases/disorders such as dwarfism. While many instances of selective breeding have benefits in specific categories, most cases of selective breeding within animals specifically have too many negative repercussions.

How Does It Work?

According to Yourgenome.org, selective breeding is “…use of existing, naturally present gene variants in a species and the natural process of breeding.” Unlike regular reproduction, selective breeding is controlled.

People take animals with existing specified characteristics, breed them, and then take the offspring that show the best trait-expressing offspring to continue this cycle generationally to increase the chances of those species having the desired traits. Since selective breeding constantly makes one trait the most prominent in a species, this reduces genetic diversity, which is crucial for animal populations’ health, adaptability, and survival skills.

Types of Selective Breeding

Inbreeding – Reproduction between closely related individuals specifically to preserve certain animal characteristics. It can preserve or reduce genetic diversity. Due to the higher relation rate, inbreeding increases the risk of genetic disorders. If excessive or without proper management, inbreeding can lead to a decline in the fitness and viability of offspring due to inbreeding depression.

Linebreeding – Reproduction between individuals that share a common ancestor. This is usually done to get organisms to “discard” a trait or fix an existing trait. It only reduces genetic diversity. This usually increases the risk of genetic disorders but doesn’t usually have closely related organisms in the breeding process. By strategically selecting which individuals to breed and managing the level of relatedness, breeders can achieve the desired traits in offspring while minimizing the risks of genetic defects and health issues.

Crossbreeding – Reproduction between two animals from different breeds or varieties of the same species. Crossbreeding is often done for various reasons, including inducing hybrid vigor, which means increasing the production of certain traits by crossing genetically different individuals. Eliminating recessive diseases is also another reason. Combining positive traits can also be an outcome of crossbreeding. Unlike the other two, this type of selective breeding does not usually take blood-related animals, which decreases the rate tremendously for the risks of genetic defects.

Negative Health Repercussions

Genetic Disorders and Physical Issues:

Selective breeding, especially falling under the inbreeding category, can affect offspring the same way incestual reproduction can. Selective breeding that created the hundreds of modern dog breeds has put purebred dogs at risk for many health problems, affecting both body and behavior. For example, when owners purposely bred dogs to have “aesthetically pleasing” traits such as flat faces, droopy eyes, or squished faces, they came with many disabilities. Having flat faces causes animals more difficulty breathing, and having such low-hanging eye sockets causes various eye injuries and infections. This trait is shown in Pugs, Bulldogs, Persian cats, Himalayan cats, etc.

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Another example of this repercussion can be seen in thoroughbred horses, who were bred to have lighter bones (in terms of weight) to fasten their speed for races and competitions, which causes that particular horse breed to keep breaking their ankles and legs constantly.

Reduced genetic diversity:

Selective breeding usually results in populations with many similar characteristics. This means that if one animal in a species has a deficiency/flaw, the whole population is most likely to have said weakness. For example, certain infections have a greater chance of spreading through populations with similar genetics since they don’t have immunity to the same diseases. CPV is one of those diseases. It is highly contagious and deadly and can be seen in breeds like Rottweilers, Doberman pinschers, Labradors, and German shepherds due to their genetic predispositions. Studies show that outbreaks of the Canine Parvovirus were more prominent in purebred populations due to the reduced genetic diversity. The mortality rate of this virus can reach up to 91% in infected dogs and, with treatment, around 80-90%. (According to https://canineparvovirus.org/survival-rate/)

Ethics

Source: https://www.mspca.org/animal_protection/farm-animal-welfare-chickens/

Exploitation for human needs: Intense breeding practices prioritize yield over animal health. Selective breeding has been used for a long time to meet human demands for “higher productivity.”

Processes only focused on the outcome of profit, such as faster growth or increased milk production, can lead to harmful health defects. Animals bred for these traits usually always suffer from chronic health issues such as organ failure from stress that goes beyond physical limitations. This practice throws animal health under the bus to expand their economic gain while constantly trying to be justified.

In Conclusion…

Selective breeding, which can offer advancements in “productivity” and help enhance some positive traits, has significant biological and ethical repercussions. Reducing these harmful practices can be done through thoroughly monitored regulations, genetic testing, and education free to the public to discourage harmful breeding practices. Encouraging different practices, like outcrossing rather than inbreeding, can help increase genetic diversity and prioritize animal welfare and general health over profit gain or “aesthetics.” With more awareness and serious action, we can help our society shift towards different breeding approaches that actually respect these animals’ well-being and ensure they can thrive and survive without compromising them for the sake of human convenience.

Sources:

Encyclopædia Britannica, inc. (2024, October 25). Selective breeding. Encyclopædia Britannica. https://www.britannica.com/science/selective-breeding
Your Genome. (2024). What is selective breeding? Www.yourgenome.org. https://www.yourgenome.org/theme/what-is-selective-breeding/
‌BBC. (2019). Variation – AQA – Revision 3 – GCSE Biology (Single Science) – BBC Bitesize. BBC Bitesize. https://www.bbc.co.uk/bitesize/guides/zsg6v9q/revision/3
‌Survival Rate – Canine Parvovirus – Treated VS. Untreated (Diagram). (n.d.). Canine Parvovirus. https://canineparvovirus.org/survival-rate/
‌Inbreeding vs. Line Breeding – What’s the Difference? | This vs. That. (2023). This vs. That. https://thisvsthat.io/inbreeding-vs-line-breeding
‌Crossbreeding Systems for Beef Cattle | Mississippi State University Extension Service. (n.d.). Extension.msstate.edu. http://extension.msstate.edu/publications/publications/crossbreeding-systems-for-beef-cattle
‌PBS. (2010, September 16). Dogs That Changed The World | Selective Breeding Problems | Nature | PBS. Nature; PBS. https://www.pbs.org/wnet/nature/dogs-that-changed-the-world-selective-breeding-problems/1281/
‌PBS. (2010, September 16). Dogs That Changed The World | Selective Breeding Problems | Nature | PBS. Nature; PBS. https://www.pbs.org/wnet/nature/dogs-that-changed-the-world-selective-breeding-problems/1281

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