Selection systems

Question 1

the who for selection of breeding stock

Answer 1

-individual
-relative:
-ancestors, siblings, progeny

Question 2

the how for selection of breeding stock

Answer 2

-independent culling levels
-tandem selection
-index of weighted traits

Question 3

correction factors

Answer 3

-sex
-age of dam
-age of calf
-singleton vs twin

Question 4

individual selection=mass selection

Answer 4

-based on animals own performance
-accuracy=square root of h^2
-practical if trait:
-is measurable
-expressed early

-eample goal: increased av daily gain

Question 5

ancestor selection=pedigree selection

Answer 5

-based on weighted average of ancestors
-closer relatives are more genetically simular
-useful if trait is not expressed early

Question 6

how to measure accuracy of how a trait is inherited

Answer 6

-square root of h^2
effective if h^2 is high

Question 7

ancestor selection

Answer 7

-use if individual is not available
-use at least 1 relative on both the dam and sires side of the pedigree (same relatives for each individual)
-use closest relative available
-use mean of many records
-accuracy is low, cost to conduct is cheap

Question 8

sibling selction

Answer 8

-can come close to accuracy of individual selection
-0.71 (max) for full sibs
-.5 (max) for half sibs
-need 15-20 sibs for best estimate
-example decreased packfat in pigs
-ultrasound all piglets
-retain gilts from best litters
-note sibs should have similar environment