Improvement of the Animal Population - Genetics and Selection Flashcards

Fundamental vocabulary terms related to animal genetics, heritability, and selection methods in livestock production.

Breed

A subgroup within a species developed over time through selective breeding, where animals share common physical characteristics, performance traits, and a consistent genetic background.

Species

The broadest natural grouping of animals that can mate and produce fertile offspring.

Selection

The process of choosing specific animals to be parents of the next generation based on traits the breeder wants to improve or maintain.

Natural Selection

A process occurring in nature without human intervention where animals with traits better suited to their environment are more likely to survive and reproduce.

Artificial Selection

Also known as selective breeding, it is when humans intentionally choose which animals to breed based on desirable traits like faster growth or higher milk yield.

Additive Gene Effects

Occur when the individual effects of alleles simply add up to influence a trait; these effects are consistent, heritable, and the main focus of selection programs.

Non-Additive Gene Effects

Genetic variations involving interactions between genes, such as dominance and epistasis, which are often not passed on consistently but are important for hybrid vigor.

Dominance

A type of gene action where one allele masks the effect of another at the same gene location.

Epistasis

A type of gene action where genes at different locations interact, with one gene suppressing or enhancing the effect of another unrelated gene.

Heterosis

Also known as hybrid vigor, this refers to the desired result of non-additive effects in crossbreeding programs.

Heritability ($h^2$)

The proportion of variation in a trait among animals that is due to genetic differences rather than environmental factors, expressed as a value between $0$ and $1$.

Low Heritability ($0.0 - 0.2$)

Interpretation indicating that a trait is mostly influenced by the environment rather than genetics.

Moderate Heritability ($0.2 - 0.4$)

Interpretation indicating that both genetics and environment play roles in the variation of a trait.

High Heritability ($0.4 - 0.7+$)

Interpretation indicating that a trait is strongly influenced by genetics and is a good candidate for selection.

Breed Associations

Official organizations that register purebred animals, maintain pedigree records, and provide standardized genetic evaluation reports.

Estimated Breeding Value (EBV)

A measure of an individual animal’s genetic potential to pass a specific trait to its offspring, based on its own performance and data from relatives.

Expected Progeny Difference (EPD)

A prediction of the average difference in performance between the offspring of one animal and the offspring of another, commonly used in beef and swine industries.

Tandem Selection

A breeding method focused on improving one trait at a time; simple to use but slow in overall progress.

Independent Culling Levels

A selection method where animals must meet minimum standards for all selected traits to be kept for breeding; failing one trait results in the animal being culled.

Selection Index

A method that calculates a numerical score for each animal by combining multiple traits weighted by economic importance or heritability.