37) Practice of selection: forms of selection, selection index, correlation

Question 1

Selection is base on

Answer 1

• Origin of info
• Aim and direction of selection
• Correlation between traits
• No. of criteria

Question 2

Origin of information

Answer 2

• Performance
• Phenotypic selection
• Pedigree
• Collateral relatives

Question 3

Aim and direction of selection

Answer 3

• Aim to increase average performance (positive)
• Bidirectional: Either choose extreme positive or negative animals
• Multidirectional: Improve several traits together

Question 4

Correlation between traits

Answer 4

• Correlations may be:
  
  • Positive
  • Negative
• Select a trait - Possible to influence another trait’s frequency

Question 5

No. of criteria

Answer 5

1. Select for milk production
2. Select for milk fat
3. Select for production

Question 6

Selection index

Answer 6

Indicates the total value of a trait

Question 7

Index selection

Answer 7

Several positive traits are chosen simultaneously

• Each trait assigned a valued importance
  
  • Weight is a 10, colour is a 1
• Value multiplied by observed trait in each individual