Population Genetics Farm

Question 1

How does the modern dairy cow differ to an old style of cow?

Answer 1

^ milk yield
v fertility
v health
v utility or robustness

Question 2

How do quantitative genetic traits differ from qualittiative?

Answer 2

Can be measured, but often based on 1000s of genes which are usually NOT KNOWN
- select based on phenotypic trait not distinct bit of DNA

Question 3

Give 3 types of dairy system

Answer 3

• ^ input/output
• pasture based
• niche markets eg. organic, soil association guidelines etc

Question 4

What is a selection index?

Answer 4

Multiple traits combined and weighted for importance and interaction between them eg. productivity index = milk yield, fertility etc.

• often given in terms of monetary value
• may incoroporate welfare, temperament etc

Question 5

What are EBVs called in the dairy industry?

Answer 5

PTA (predicted transmitting ability)

Question 6

What are the majority of dairy cows nnowadays?

Answer 6

> 90% holstein only 10% fresian (black and whites)

Question 7

What is PIN?

Answer 7

Production index = kg milk, milk fat, protein

Question 8

How is fertility measured in the dairy industry?

Answer 8

Calving interval

Question 9

What is £PLI?

Answer 9

Profitable Lifetime Index 
- milk PTA
\+ fat PTA
\+ protein PTA
\+ lifespan PTA
- SCC PTA
\+ locomotion PTA
> each will have an associated value, so 1 unit ^ characteristic affects £PLI by x amount

Question 10

How does SCC PTA affect the merit of a bulls £PLI?

Answer 10

negative is good!

• 15% = decrease daughters SCC by 15%
• SCC good predictor of mastitis

Question 11

How are production, health and fertility traits linked? How does this impact bull choice?

Answer 11

• milk, fat, protein ^ mastitis
• milk, fat, protein ^ lameness
• milk, protein ^ fertility CI
• fat ^ fertility CI
  > want a bull that breaks these correlations as all are negative!!
  > selction index identifies bulls that go against these correlations eg. those with ^ milk yield but v calving interval

Question 12

How is a fertility index formulated?

Answer 12

Combine a fertility trait PTA (or multiple traits) with relative economic value eg. FI = -0.31(CI) +1.56(Non-return rate) to give an economic approach to choosing bulls

Question 13

How has the £PLI recently been improved?

Answer 13

Broaden the breeding goal - include fertility, revision of economic values [dairyCo], condition score and environmental sensitivity [Robust cows]

Question 14

What outputs are aimed for in the future dairy cow?

Answer 14

Milk of the right composition and produced the right way (consumer driven)
Less calves and less cull cows
Imprived welfare and environmental impact
^ profits

Question 15

Why is genetic improvement particularly viable in the dairy industry?

Answer 15

AI

Question 16

Give examples of the traits scored for holstein classification process

Answer 16

stature
rump width, angle
udder 
milk 
foot angle 
chest width 
temprament