Genetics and Horse Breeding Flashcards
what is selection
- causing or permitting some individuals to produce more offspring then others
- human-directed selecting, human selection does the same thing but in with different goals
factors in selection
- breed or dont breed = when you breed there should be a reason
- how many offspring
No thoroughbred can be registered without natural conception, why?
- stops inbreeding (partially)
- keeps the stud feed high
what are focal traits
-performance
- conformation
- temperament
- trainability
- genetically clean
what type of traits are most selective criterias
- quantitative traits
- measured on a continous scale
- polygenic
- phenotypic is function of genetics and environment
what are examples of quantitative traits
- conformation
- performance
- longevity
- fertility
- height
- weight
- angle of pelvis
- cow sense
- quality of trot
jumping ability - environment = management, trainer, rider
what happens with variance
- if theres two little phenotypic selection - not a lot to choose
if the phenotype is similar the genotype is likely too similar
what creates phenotypic variance
genotypic variance + environmental variance
what is the purpose of selection
- direct change in some characteristic(s) of the population which exhibit genetic and phenotypic variation
what is the effect of selection
- change in frequency of allele (s) that influence trait(s) being selection
- traits may be selected directly or indirectly
what happens during selection success
- imporvement (change) in trait (s) for population
- changes the mean
- reduces the variance
what determines a response in selection
depends on heritability and selection intensity
rate also depends on generational interval
- proportion of difference between animals due to differences in genotypes
what is considered good heritability
- environment are identical h2=1.0
- if all animals are clones h2=0.0
- measure of how much of differences between animals are due or not due to genetic differences
what is taken into consideration for breeding stock selection
- heritability
- generation interval
- selection intensity
what are other breeding stock selections considerations
- indirect selection effects
- inbreeding
what can a good performance record do
- good indication of genetic value if the traits are heritable
how heritability
<0.2
moderate heritability
=0.25
high heritability
> 0.2
what is a relationship
- proportion of genes in common between individual and acestor cited in pedigree
what is the order of thins for production and traits
conformation
athleticism
performance
what are peripheral traits
longevity
temperament
trainability
what is taken into consideration for breeding stock selection
- individual performance record
- relatives performance record
- peripheral traits
- free of genetic defects
- choose traits to select for set criteria
- determine relative emphasis to place on each trait
what are common defects
- hernias
- cryptorchadism
- parrot mouth
- cataracts
- heaves
- DOD
- ER
- ligament desmitis
