dairy selection

Question 1

cross breeding in dairy

Answer 1

• Relatively little : some intreats to improve reproduction
• Milk production is the first objective
  . Pounds of milk - Holstein is superior
  . %milk fat - jersey is superior

Question 2

Why is selection based primarily on sires ? Why are sires so important when all important traits are sex-limited ?

Answer 2

• Number of progeny vs. dams
• AI allows for even larger number of progeny (45% of operation have no bulls )
• Selection based in close female relatives and progeny testing of offspring

Question 3

DHIA what does it stand for and what is it

Answer 3

( national dairy herd improvement association )

• System of records
• Use modified contemporary comparison
  . Records of performance to account for variation in performance if possible

Question 4

what does PTA stand for and what is it used for ?

Answer 4

(predicted transmitting ability )
select sire based on this

Question 5

success of dairy industry

Answer 5

AI, Environmental control to optimize environment to maximize production , bST ,

Question 6

what is bST

Answer 6

• Naturally occurring hormone in cow
• Major regulator of milk production
• admisitoring of exogenous bST ( posilac) can increase milk production

Question 7

what does adequate nutrition effect?

Answer 7

• increases IGF-I - increases milk

Question 8

what does non adequate effect?

Answer 8

no change in IGF-I - no change in milk

Question 9

what is genomics

Answer 9

. The large scale used of DNA information to estimate the genetic merit of cattle

. This includes knowledge of differences in DNA sequences of individual cattle and association these differences with actual performance

. Genetic map of war traits animal inherited from each of its parents is available and summarized into genomic evaluations

. Includes the combination of their PA and genotypic data, providing more reliable results.

Question 10

name type traits

Answer 10

1. Stature
2. Strength
3. Body depth
4. Dairy form
5. Rump angle
6. Rump width
7. Rear legs - side view
8. Rear legs
9. Foot angle
10. Feet and leg score
11. Fore udder attachment
12. Rear udder height
13. Rear udder width
14. Udder clept
15. Udder dept
16. Front teat placement
17. Rear t teat placement
18. Teat length
19. Udder composite
20. Feet and leg composite