Outbreeding Flashcards
Outbreeding
Mating of individuals less closely related genetically than the average of the population
Within a breed
Opposite of inbreeding
Poultry
Big in this industry
Several lines combined together for desirable traits
Grading up
“top crossing”
Mating purebred males with non-purebred females
Goal: to make a purebred population
[Takes generations]
Crossbreeding
crossing different breeds to combine desired traits
Species crosses
Closely related species
Ex: horse x donkey = mule
Genetic affect
increase heterozygosity
keeps more deleterious recessives in heterozygous form, which means they are present but not expressed in phenotype
Phenotypic affect
Heterosis
Hybrid vigor
[Opposite of inbreeding depression]
Effects of Outbreeding
The degree of superiority of the outbred offspring for a particular trait as compared to the average of the parental line/breed
Meat Animal Production
crossbreeding used by most commercial producers (ex: beef, sheep, hogs)
Often, crossbreeds will not exceed the purebred parent for individual traits such as survival, growth rate, feed efficiency, and carcass merit
Heterosis
For all the traits contributing to the overall production efficiency will cumulate and result in crossbreds with greater net economic merit that the best average straightbred
Breed complementation
Combining the desirable traits of 2 or more breeds into same offspring
The degree of heterosis and complementarity
Depends on Genetic relationship of parents and Trait heritability
Trait heritability
Measures the strength of the relationship between performance (phenotypic value) and breeding values (genotypic) for a trait in a population
Genetic Relationship of Parents
The more genetically diverse the parents are, the greater the expression of heterosis and complementation
Heritability vs Heterosis
Has an inverse relationship
Ex: When one is high, the other is low
Major uses of outbreeding in livestock industry
General - maximum production of offspring
Specific - Commercial cow/calf, Swine, Poultry, and Sheep
Outbreeding in Commercial cow/calf
Almost all commercial cows are crossbreds
Ex: black baldy
Outbreeding in Swine
Extensive crossing of inbred lines and breeds to maximize reproduction and ground from maternal lines
Reciprocal recurrent selection
system of selection for increasing the combining ability of two lines that have demonstrated past crosses that have combined well
Net result
Development of genetically diverse inbred lines
better performing crossed lines would express greater heterosis
Outbreeding in Poultry
meat breeds use crossbreeding for growth advantages
EX: male selected for growth and meat, female selected for maternal characteristics
Outbreeding in Sheep
Meat breeds
[Prices favorable in the spring, when winter lambs are ready for market]
Limited Outbreeding in Dairy
Outcrossing within breeds, but rarely between breeds (Not cost effective or efficient)