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

What is the effect of increased DMI in the lactating dairy cow?

Answer 2

• once negative E balanced is passed, cow must increase DMI to keep producing milk
• increased DMI–> increased blood flow to mesenteric veins/liver –> metabolism of progesterone/estradiol in liver (decrease)–>
  
  • decreased estrous behavior
  • increase size of ovulatory follicle
  • increased double ovulation
  • decrease embryonic development
  • decrease preg rate
  • increase preg loss

Question 3

What is the main focus of reproductie management of dairy cattle?

Answer 3

• proactively work with groups of open cows
• reduce potential for “lost opportunity” with systematic breeding
• Goal is to “speed up” establishment of pregnancy
• main objectives:
  
  • increase AI submission rate
  • increase pregnancy rate

Question 4

Parameters used for evaluation of reproductive performance

Answer 4

• AI submission rate (estrous detection rate)
• pregnancy per AI
• pregnancy rate** (main measurement of repro efficiency)
• pregnancy loss

Question 5

AI submission rate (estrous detection rate)

Answer 5

• number of cows detected in estrus/number of eligible cows to be in estrus (recieve AI; non-pregnant cow) in 21 day period
• doesn’t include pregnant cows or cows undergoing uterine involution

Question 6

pregnancy per AI

Answer 6

• number of cows pregnant /number of cow inseminated

Question 7

pregnancy rate

Answer 7

• number of pregnant cows/number of cows eligible to become pregnant in 21 day period (rate)

Question 8

pregnancy loss

Answer 8

• number of cows not pregnancy/ number cows diagnosed pregnant

Question 9

as pregancy rate _________, calving to conception interval ____________

Answer 9

increases

decreases

• increase in pregnancy rae increases annuity value/cow/year

Question 10

main objective of all dairy herds

Answer 10

• MAXIMUM PROFIT, irrespective of production operations (low input, high input, low effort, etc)

Question 11

Explain reproductive efficiency impacts on profitability

Answer 11

• determines culling policies (more aggressive voluntary culling of less profitable cows)
• stringent selection of better replacements
  
  • greater number of heifers bringing in first lactation to choose from (no need to purchase replacement heifers)
  • faster genetic improvement
• increase % of heard _>_2nd lactation
  
  • reduce inventory fo replacement heifers (23% total cost)
  • greater milk yield
• improve milk yield (88% revenue) and income over feed cost (IOFC) (48-50% total cost)

Question 12

improved reproductive performance also improves

Answer 12

• control of cost and milk yield
• IOFC= income from milk yield/cost of feeding cows
• Profit is difference between income from milk yield and cost to feed bows
• IOFC is higher in early lactation because that is when cows are most efficient (3/1) but begins to diminsh as lactation progresses (2/1)
• first 100 days is highest efficiency of lactation (want cow to spend as much time as possible here)
• with each calving, cow has another opportunity to enter this 100 first days of high efficiency
  
  • a long calving interval reduces the % time spent in high efficiency lactation
  • a short calving interval increases % time in high efficiency lactation
  • GET COW PREGNANT ASAP

Question 13

Explain the difference in a conception at 75 DIM vs 195 DMI

Answer 13

• conception at 75 DIM
  
  • milk for about 220 days
  • stop milking (dry) at ~295 days
  • ideal
• conception at 195 DIM
  
  • have to extend late lactation period
  • continues to decrease in milk production
  • increase body reserves (becomes fat)
  • not ideal

Question 14

The cycle of cow-calf operations

Answer 14

• calving (day 0)——-rest period——(day 40-60)——–breeding season——(80-120; lactation)————-gestation———–(270-300)—–(325-405)

Question 15

factors that can impact repro efficiency in dairy and beef cows

Answer 15

• postpartum group (0-45 days)
  
  • early postpartum stress (suckling induced gonadotropin inhib)
  • dystocia, poor nutrition, retained placenta, uterine infection, metabolic disorders, ovarian cysts
    
    • these can interrupt/prolong uterine involution –> less profitable breeding season

Question 16

If delayed calving occurs, what are your options?

Answer 16

• shortened rest period (average interval to resumption of cyclicity 30-40d and heifers=60d)
• reduced breeding season
  
  • excessive culling of open cows
  • excessive retention of female calves for replacement (costly)
• prolonged next breeding season or no breeding season
  
  • reduced performance of calves (survival, birth weight, weaning weight)

Question 17

Summary: optimization of dairy/beef management

Answer 17

• high first service pregnancy per AI

1. increases % preg early in breeding season –> decrease distribution of calving dates
2. decrease # heifer calves retained –> decrease feed costs
3. decreases replacement rate –> decrease # younger cows

• all 3 of these –> increase calf weaning weights = increase net income

Question 18

Timeline approach from calving to the end of VWP to optimize repro efficiency

Answer 18

• transition period
  
  • dairy: last 21 days of gestation to 21 DIM (after calving)
  • want to reduce incidence of diseases, minimize BCS loss, expedite resumption to cyclicity
    
    • provide comfort: heat stress abatement, sufficient resting space
    • proper nutrition: avaliability of water, balanced and sufficient feed for ALL (minimize competition)
• ~day 50= end of VWP, start of repro

Question 19

voluntary waiting period

Answer 19

• 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 20

estrogen’s effect on immune system?

progesterone’s effect on immune system?

Answer 20

enhances immune function

inhibits immune function

Question 21

effect of periparurient diseases on reproductive efficiency

Answer 21

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

Question 22

timed AI programs

Answer 22

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