Bovine Breeding Management

Question 1

reproductive efficiency of lactating cows

Answer 1

• influences the profitable operation of a dairy farm
• optimize profit through combination of
  
  • days that cow spends in the most efficient time of the lactation curve
  • cull rate due to reproductive failure

Question 2

main factors that determine reproductive performance in dairy herds:

Answer 2

• voluntary waiting period (VWP)
• insemination rate
• pregnancy per AI
• pregnancy loss

the outcome of these factors depends on the reproductive program of herd

Question 3

reproductive programs on dairy herds

Answer 3

• focused on hormonal manipulation of estrous cycle to obtain pregnancy in timely manner at end of VWP
• need to integrate theriogenology and herd health to optimize reproductive performance

Question 4

4 reproductive indices that determine reproductive efficency of dairy herd

Answer 4

• VWP
• estrous detection rate
• conception rate
• pregnancy loss

Question 5

estrous detection rate

Answer 5

number of cows detected in estrus/number of eligible cows to be in estrus

Question 6

pregnancy per AI

Answer 6

number of pregnant cows/number of inseminated cows

Question 7

pregnancy rate

Answer 7

number of pregnant cows/number of eligible cows to become pregnant

true rate changes daily, but is typically evaluated at 21 day intervals

Question 8

as pregancy rate _________, calving to conception interval ____________

Answer 8

increases

decreases

Question 9

voluntary waiting period

Answer 9

• establishment of pregnancy after parturition depends on anatomical and functional return of genital tract to its pregravid state
  
  • uterine involution
  • early onset of ovarian cyclicity

Question 10

estrogen’s effect on immune system?

progesterone’s effect on immune system?

Answer 10

enhances immune function

inhibits immune function

Question 11

VWP depends on:

Answer 11

• ideal interval to pregnancy
  
  • milk production
  • persistence of lactation
• pregnancy rate
• reproductive program for first AI
• fertility of first AI

in general > 50 DIM

Question 12

altering VWP

Answer 12

• to delay past 70 d postpartum and maintain same reproductive performance (days open):
  
  • requires total control at first AI (timed AI)
  • pregnancy per AI should increase by 8-10 percent points for every estrous cycle delay in VWP

Question 13

estrous detection rate (AI submission rate) determines:

Answer 13

determines when cows are first AI at the end of VWP

Question 14

what strategies are used to correct and reverse low reproductive efficiency?

Answer 14

• improve environment of cow
• improve how employees deal with cows
• implement genetic selection program to improve health and fertility
• minimize postpartum (60d) diseases to improve fertility**
• implement reproductive mgmt to improve PR**

Question 15

effect of periparurient diseases on reproductive efficiency

Answer 15

• takes longer to cycle
• reduced pregnancy at end of VWP
  
  • lower CR
  • takes longer
• increased risk for pregnancy loss

Question 16

timed AI programs

Answer 16

• improve reproductive performance
  
  • AI submission rates increase
• increases yearly profit compared to estrous detection along
• lower cost per pregnancy in general

Question 17

synchronization of estrus

Answer 17

• day 0: PGF_2alpha
• day 14: PGF_2alpha
• day 16-21: AI

Question 18

OvSynch TAI Protocol

Answer 18

• day 0: GnRH
• day 7: PGF_2alpha
• day 9: GnRH
• day 10 (16 hrs): TAI

best at beginning of cycle

GnRH -> release of LH -> ovulation

Question 19

Presynch-Ovsynch

Answer 19

• day 0: PGF
• day 14: PGF
• day 26: GnRH
• day 33: PGF
• day 35: GnRH
• day 36: TAI

Question 20

after any given breeding

(for dairy cows)

Answer 20

• 25-45% of cows become pregnant
  
  • 55-75% need to be rebred
• nonpregnant cows need to be re-inseminated as early as possible for optimum repro performance
• until a cow returns to estrus or is diagnosed as nonpregnant: no action can be taken!
• pregnancy dx as early as possible (100% sure its open)

Question 21

what to do for cows not seen in estrus after AI attempt?

Answer 21

• palpate at d 35-42
• u/s at d 26-32
• chemical dx at 32 d

Question 22

timeline from calving to end of VWP to optimize reproductive efficiency in dairy herd

Answer 22

• -21 days
  
  • nutrition transition period: lower calving related problems
• day 0
  
  • calving
  • early dx and tx of diseases, mantain BCS, control diseases
• +50 day
  
  • end of VWP
  • increase PR

Question 23

beef cattle breeding managment

Answer 23

• breeding season 60 to 90 days
• pregnancy examinations ~45 days at end of breeding season
• pregnancy rate = # cows pregnant/# cows with bulls during breeding period
  
  • >80%
• maintain 12 month calving interval
• can become pregnant sooner than dairy cows

Question 24

factors that affect reproductive efficiency in beef cattle

Answer 24

• cow health
  
  • infectious diseases, body condition, nutritional reqs
• bulls
  
  • bull to cow ratio
  • health
  • reproductively sound (BSE)