Genetics - practical considerations

Question 1

What is heritability?

Answer 1

proportion of phenotypic superiority of the parents that is seen in their offspring
h2 = 1 - all superiority of parents is passed on to offspring
h2 = 0 - none of the superiority of the parents is passed on to offspring

Question 2

What factors have allowed a large increase in genetic potential in dairy cow breeding

Answer 2

Accurate recording of milk yields
Development of AI industry
Development of techniques to estimate breeding value of dairy cattle

Question 3

What is PTA/predicted transmitting ability?

Answer 3

the amount of a particular trait an animal is predicted to pass on to its progeny
Expressed as an average for the breed
also known as estimated breeding value (EBV)

Question 4

what are type/physique traits?

Answer 4

stature, body depth, foot angle, udder attachment, teat length etc.

Question 5

What are the genetic indexes

Answer 5

Combination of a number of individual traits
Profitable lifetime index:
- economic index
- combines PTAs for production with survival, fertility, udder and leg health, calving and efficiency
Fertility index:
- calving interval, non return rate, BCS, days from calving to first insemination, number of insemination to get in calf

Question 6

Describe the use of PLI (profitable lifetime index)

Answer 6

Balanced approach
Promotes yield and maintains milk quality
Increases emphasis on fertility
Improves functional type
Increases emphasis on longevity
Reduces maintenance costs
Improves udder health and lameness
Improves calving performance

Question 7

What are the priorities of breeding selection?

Answer 7

Driven by profitability
selection of bull most appropriate for cows and business
improve combination of traits
use a spread of proven sires across herd to reduce risk
avoid low PLI sires