Pedigrees Relationships
A diagram defining the relationship between animals due to kinship
Pedigree
The ability of an individual to produce progeny whose performance is especially like its own and/or is especially uniform
Prepotency
An increase in performance of hybrids relative to that of purebreds
An increase in the performance of hybrids over that of purebreds from linebred families
Crossbreeding
Linebreeding
Superiority of an individual offspring to the average of the parental breeds
Hybrid vigor (heterosis)
Composite breeds def
aims to create a stable breed with maintained heterosis
The mating of relatives
Inbreeding
The mating of individual within a particular line to maintain a degree of relationship to particular ancestor (mild form of inbreeding).
Linebreeding
What can fix lowly heritable traits
crossbreeding
Crossbreeding systems
2. terminal crossbreeding systems
3. composite crossbreeding systems
Advantages and challenges of composite breeds
Advantages:
1. Hybrid vigor: enhance growth, fertility, survivability
2. Environment adaptability: suited to specific climates
3. Production Efficiency: Better carcass yield, feed conversion
4. Genetic Diversity: Less inbreeding, increased vigor
Challenges:
1. trait stability: consistent performance across generations
2. Managing genetic drift: control for undesired traits
3. Variability in crosses: unpredictability in offspring traits
An ancestor common to more than one individual (appears more than once in a pedigree
1. increase in # of homozygous loci in individuals
2. increase in the frequency of homozygous genotypes
3. increase homozygosity of deleterious recessives
Forms to increase in Homozygosity
Take 1 trait from each parent to make superior offspring OR use 1 trait to fix bad trait
Breed complementarity
Terminal crossbreeding systems def, advantages and disadvatages
Def: a system in which maternal-breed females are mated to paternal-breed sires to efficiently produce progeny that are especially desirable from a market standpoint.
Advantages:1. 100% heterozygosity
2. more lbs
Disadvantages:
1. purchase straight bred ewes
Breeding strategies in composite breeding
2. rotational and terminal sire systems
3. selection and culling
contributes 1/2 each
Contributes 1/4 each
Contributes 1/8
Parents
Grandparents
Great-Grandparents
The reverse of hybrid vigor--- a decrease in the performance on inbreds, most noticeably in traits like fertility and survivability
Inbreeding depression
1. Direct
2. Maternal
3. Parental
A system in which generations of females are rotated among sire breeds in such a way that they are mated to sires whose breed composition is most different from their own
Advantages and disadvantages of Pure composite systems
Advantages:
1. Simplicity
2. One breeding pasture
3. provides replacements
Disadvantages:
1. lower level of heterosis
2. availability of animals
Two genes are (blank) if they are copies of the same ancestral gene
Genes have the same state/function but are NOT necessarily from the same ancestral copy
Identical by Descent (IBD)
Alike in State (AIS)
Measurement of the genetic contribution of a common ancestor to an individual
An expression of the relationship of 2 individuals
The probability that both genes at a locus in individual X are identical by descent
Inbreeding coefficient
Coefficient of relationship
Fx
Mating a hybrid to a purebred of a purebred of a parent breed or line
Backcrossing
Forms of crossbreeding systems
1. 2-way rotation
2. rotate sire breeds3. three-breed rotation
Examples of composite breeds in beef cattle
1. Santa Gertrudis (5/8 shorthorn, 3/8 brahman)
2. Beefmaster (Hereford, shorthorn, brahman)
3. Brangus (3/8 Brahman, 5/8 Angus)