What is Breeding?
To define breeding in animal husbandry, horticulture, and agriculture, it is the application of genetic concepts to enhance desirable qualities. Ancient agriculturists improved several plants via selective cultivation. Pollen from the chosen male parent, and no other pollen, should be passed to the chosen female parent, according to modern plant breeding centres.
Animal breeding involves choosing the ideal trait (for example, high milk production, fine wool), selecting the breeding stock, and describing the breeding system (for example, inbreeding, and crossbreeding). This is the breed definition of biology.
Selective Breeding
Selective Breed Definition Biology
Selective breeding is defined as the process, where humans control the breeding of organisms to eliminate or exhibit a specific characteristic. This type of breeding uses artificial selection to direct genetic transfer of the desirable traits. As opposed to natural selection, selective breeding mainly focuses on traits that will benefit humans.
Selective Breeding Overview
The process entails recognising certain attractive characteristics and locating two members of a species that display certain characteristics. Then, a series of breedings or matings is performed between the individuals with the favored features to form offspring, which exhibit the feature and that may be used for the future matings. The desirable phenotypic traits are then passed from parents to offspring through their genes.
While selective breeding may increase the prevalence of desirable traits by increasing the frequency of favourable genes in the gene pool, inbreeding can also increase the prevalence of undesirable traits that can cause hereditary health problems.
The word ‘artificial selection’ was first coined by Charles Darwin, in his own book, “On the Origin of Species” to define how humans had mirrored the process of natural selection via selective breeding. Darwin has recognized that the forces changing population were the same, but instead of the organisms adapting to the environment artificial selection can be driven by the human needs. Oftentimes, this leads to a decrease in fitness of the organisms due to the reason that adaptive traits can be ignored.
Selective Breeding Examples
Dogs
All modern dogs have been selectively bred by humans around thousands of years. Dogs were first bred from the common ancestor of gray wolf (which is Canis Lupus) that was domesticated by the humans with whom it lived in nearby proximity. It is also speculated widely that these animals were first domesticated by the humans for protection and hunting, although all the modern dogs have been bred for multiple reasons, such as performing particular tasks, companionship, for aesthetic purposes, or for entertainment. Now, there are about 400 breeds of dog, which means that they have the widest phenotype range of any mammal.
The highly specific traits, which are selectively bred into dogs can come at a huge disadvantage to their health. Not only could a lack of genetic variation within the gene pool trigger certain inherited health issues, but dogs bred with intentionally accentuated physical features which also suffer from their unnatural physical shape. For example, the ‘flat-faced’ breeds and bulldogs can suffer from breathing problems, while some large dogs commonly suffer from bone tumors because of their excess body weight.
Plants and Livestock
Almost all of the food, which is consumed by modern humans has been selectively bred about thousands of years. Around 10,000 years ago, when the humans began living in either semi-permanent or permanent settlements, they started to cultivate crops on their own and herd flocks of livestock firstly.
In plants, selective breeding began unintentionally selecting vegetables and fruits for qualities like sweetness and large size; seeds of plants with the desired qualities would have been given a chance to germinate through human consumption and cultivated within their latrines (or toilets).
Other desirable characteristics such as seedlessness, oil content, and fleshy texture were all altered over time, rendering most human-cultivated vegetables and fruits unrecognisable when compared to their wild equivalents. The similar process took place with domesticated animals such as chickens (considerably larger than their wild ancestors), sheep (bred for thicker wool), and the cattle (bred for increased milk yield or more muscle mass).
Hunting
Not selective breeding is beneficial to humans, always. Outside biology, selective breeding is practiced accidentally. Poachers, who hunt and kill elephants and rhinoceros for valuable ivory and rhino-horn, have in recent years caused an unintentional selection for animals with smaller tusks and horns. As the males having the largest horns are the most desirable to the hunters, the genes which control for size are being removed from the population, rapidly.
In addition, a gene mutation that results in elephants with no tusks at all is increasing within the population. With population numbers greatly reduced because of hunting pressure, it can be possible that elephant tusks could entirely disappear. This is one of the examples of the effect that pressures of modern human populations have on wildlife.
FAQs on Breeding
1. What is animal breeding in the context of biology?
Animal breeding is a branch of agriculture and animal science concerned with the selective mating of domestic animals to produce offspring with improved and desirable qualities. The primary goal is to enhance genetic traits that are beneficial to humans, such as increased milk production, better meat quality, faster growth rates, or resistance to diseases.
2. What are the main objectives of animal and plant breeding programs?
The main objectives of breeding programs are strategically aimed at improving crop and livestock populations for human benefit. Key goals include:
- Increased Yield: Producing more milk, meat, eggs, or grain per individual.
- Improved Quality: Enhancing nutritional value, taste, or appearance, such as higher protein content in wheat.
- Disease Resistance: Developing varieties and breeds that are genetically resistant to common pathogens and pests.
- Enhanced Adaptability: Creating strains that can thrive in challenging environmental conditions like drought or extreme temperatures.
3. What are the two main types of breeding?
The two fundamental types of breeding, based on the genetic relationship between the mating individuals, are:
- Inbreeding: This involves the mating of more closely related individuals within the same breed for 4-6 generations. It is used to develop pure lines and accumulate superior genes.
- Out-breeding: This is the breeding of unrelated animals. It can be further divided into out-crossing, cross-breeding, and interspecific hybridisation.
4. What is inbreeding, and what is its major disadvantage?
Inbreeding refers to the mating of closely related individuals, such as a sire and his daughter or cousins. While it is useful for creating homozygosity and preserving desirable traits, its major disadvantage is inbreeding depression. This is a condition where continued inbreeding leads to a reduction in fertility, productivity, and overall fitness due to the increased chances of harmful recessive alleles becoming expressed.
5. How is out-crossing different from cross-breeding?
While both are types of out-breeding, they differ in the breeds of the animals involved. Out-crossing is the mating of unrelated animals within the same breed that do not share a common ancestor for 4-6 generations; it is often used to overcome inbreeding depression. In contrast, cross-breeding involves mating a superior male of one breed with a superior female of another distinct breed to combine the desirable qualities of both breeds in the offspring, a phenomenon known as hybrid vigour.
6. Why is culling sometimes necessary in selective breeding programs?
Culling is the process of removing animals with undesirable characteristics from a breeding population. It is a crucial part of selective breeding because it prevents inferior or harmful genes from being passed on to future generations. By eliminating animals with traits like low productivity, poor health, or aggressive behaviour, breeders can ensure that the overall genetic quality of the herd or flock improves more effectively over time.
7. What are the major steps involved in a typical plant breeding program?
A conventional plant breeding program to create a new cultivar typically involves a systematic sequence of steps:
- Collection of Germplasm: Gathering and preserving all the different wild varieties, species, and relatives of the cultivated species.
- Evaluation and Selection of Parents: Identifying plants with the desired combination of characters from the germplasm.
- Cross Hybridisation: Mating the two selected parent plants to produce hybrids.
- Selection and Testing of Superior Recombinants: Identifying and testing the offspring with the desired trait combinations over several generations.
- Testing, Release, and Commercialisation: Evaluating the new cultivar's performance in farmer's fields and making it available for commercial use.
8. How does breeding contribute to the biofortification of food crops?
Biofortification is the process of increasing the nutritional value of crops through breeding. Instead of adding nutrients during processing, breeders use conventional or modern techniques to develop plant varieties that naturally accumulate higher levels of essential micronutrients like vitamins, minerals (e.g., iron and zinc), and proteins. For example, breeding has produced vitamin A-enriched rice (Golden Rice) and maize with higher levels of the amino acids lysine and tryptophan.
9. What is the significance of artificial insemination in modern breeding?
Artificial insemination (AI) is a key technology where semen from a selected superior male is collected and injected into the reproductive tract of chosen females. Its significance lies in its ability to overcome several challenges of natural mating. AI allows a single superior bull to sire thousands of offspring across the world, helps control the transmission of certain diseases, is more economical, and allows for the long-term storage of semen from elite sires.
10. Who is considered the father of animal breeding and what were his contributions?
Robert Bakewell (1725–1795) from England is widely regarded as the Father of Animal Breeding. He was the first to implement systematic selective breeding of livestock. His major contributions include developing the New Leicester sheep and applying principles like "breed the best to the best." He demonstrated that focused selection could dramatically improve the quality and productivity of farm animals, laying the groundwork for modern animal breeding practices.
11. How does MOET (Multiple Ovulation Embryo Transfer Technology) accelerate herd improvement?
MOET is an advanced breeding technique used to rapidly increase the number of offspring from an elite female animal. In this process, a cow is given hormones like FSH to produce multiple eggs (superovulation) instead of the usual one. She is then artificially inseminated, and the resulting embryos are collected and transferred to surrogate mothers. This allows a single genetically superior cow to produce many high-quality offspring in a single year, dramatically accelerating the improvement of herd genetics compared to the one-calf-per-year limit of traditional breeding.
