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AN SC 472 > 8 Reproductive Management of Dairy Cattle 1/2 > Flashcards

8 Reproductive Management of Dairy Cattle 1/2 Flashcards

1
Q

Slide 4

A

Look

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2
Q

When do heifers have their first pregnancy? Calving? How long does the typical Canadian Holstein cow last?

A

1st pregnancy = 15 mo
1st calving = 24 months

Lasts 2.5 lactations

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3
Q

Dairy cow estrus cycle length, duration of estrus, gestation length

A

Cycle = 21 days
Estrus = 6 to 18h
Gestation = 280 +/- 3 days

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4
Q

Typical estrus detection rates, conception rates and pregnancy rates

A

Estrus detection = <50%
Conception rate = 40% in cows, 65% in heifers
Pregnancy rate = 15-20%

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5
Q

Target age at first calving, estrus detection rate, days to first service after calving, services per conception, days open and calving interval in dairy

A

AFC = 24 months
EDR = 70%
DFSAC = <75 d
SPC = <1.8
DO = <115 d
CI = 12 to 13 mo

Slide 3**

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6
Q

Factors affecting reproductive efficiency (6)*

A
  • human (managerial)
  • animal (intrinsic)
  • environment
  • animal (extrinsic)
  • milk production
  • nutrition
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7
Q

Managerial (human) factors that can affect reproductive efficiency

A
  • elective waiting period
  • estrus detection efficiency
  • insemination time
  • synchronization protocols
  • pregnancy diagnosis
  • disease management
  • feeding management
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8
Q

How does feeding management affect fertility

A

Probability of pregnancy increases as bunk space increases (access to feed)

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9
Q

Intrinsic cow factors affecting reproductive efficiency

A
  • age & parity
  • breed/genotype
  • body condition
  • milk production level
  • physiology (hormone conc)
  • anatomical defects
  • high embryonic loss
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10
Q

Extrinsic factors affecting reproductive efficiency

A
  • infectious disease (mastitis, metritis)
  • non-infectious disease (lameness, acidosis)
  • calving related events (dystocia)
  • semen quality/sperm survivability
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11
Q

Nutritional factors that can affect reproductive efficiency

A

Energy balance, protein, starch, fats, fatty acids, vitamins, minerals

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12
Q

How does body condition affect fertility?

A

Postpartum loss in body condition impairs fertility

Extreme loss in BC = less cows pregnant to first AI, less pregnant by 150 DIM, higher pregnancy loss after first AI

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13
Q

Examples of environmental factors affecting reproductive efficiency

A
  • high ambient temperature (heat and humidity)
  • extreme cold, dampness and wind
  • pollutants/toxins in feed or water
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14
Q

What is non-return rate? What does it indicate?

A

If a cow does not return to estrus we assume they are pregnant
Indirect indicator of pregnancy

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15
Q

Ten strategies to improve reproductive performance

A
  1. Increase estrus detection
  2. Estrus synchronization
  3. Synchronization of ovulation
  4. Semen handling & AI
  5. Management factors (bunk space, dry period, VWP)
  6. Reducing embryo loss
  7. Nutritional strategies
  8. Strategic use of ultrasonography
  9. Maximize cow comfort
  10. Crossbreeding / genetic / genomic selection
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16
Q

Animal factors for poor estrus detection

A

Poor estrus expression, short duration of estrus

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17
Q

What is pregnancy rate? Example

A

Estrus detection rate X conception rate

E.g. 12 cows eligible for AI
6 detected in estrus in a 21 day period & inseminated
3 confirmed pregnant

EDR = 6/12 = 50%
CR = 3/6 = 50%
Pregnancy rate = 3/12 = 0.25

18
Q

Signs of cow in estrus

A
  • stands to be mounted
  • mucus discharge from vulva
  • riding marks
  • heat detection aid activated
19
Q

Slide 50*

A

Interval from onset of estrus to insemination affects conception

20
Q

How does footing affect estrus detection

A

Dirt provides more hours in estrus, total mounts, total stands than concrete

21
Q

Examples of estrus detection aids

A
  • Tail chalk or paint
  • Estrus alert (surface scratches off)
  • kamar heat mount detectors
  • electronic heat detection (e.g. pedometers)
  • progesterone tests
22
Q

How to induce estrus

A

Terminate luteal phase using a luteolytic agent (PGF2a)
Cows are in estrus 1 to 10 days after induction

23
Q

Devices for estrus synchronization using progesterone

A
  • CIDR (controlled internal drug release device)
  • PRID-Delta (triangle)
  • MGA (mixed in feed) - not licensed
24
Q

Advantages and disadvantages of using PGF2a for estrus synch

A

Adv: available, affordable, easy
Dis: effective only when CL active

25
Q

Adv and dis of using progesterone for estrus synch

A

Adv: tight estrus synchrony, easy
Dis: may lead to repro issues (persistent follicle), vaginal device, costly

26
Q

How does ovsynch work

A

Uses GnRH and PGF2a
Synchronizes follicle growth, regression of CL and ovulation

27
Q

How does Ovsynch 10 day protocol work

A

GnRH injection on day 0 (ovulation & new follicle growth)
PGF injection day 7 (CL regression and follicle maturation)
GnRH injection day 9 (ovulation
AI on day 10 (fertilization)

28
Q

Advantages of Ovsynch

A
  • ED not required
  • good in herds w poor EDR
  • benefits some anestrus cows
  • pregnancy rate comparable to AI at estrus
29
Q

Disadvantages of Ovsynch

A
  • handling
  • drug costs
  • less effective in heifers
30
Q

How to handle semen straws

A
  • thaw for 40 seconds in 35C
  • avoid air thawing
  • loading must be fast
31
Q

Cow insemination technique

A
  • wash/wipe clean vulva before AI
  • sanitary sheath over AI catheter
  • deposit semen in uterine body
  • inseminate ~ 12h after onset of standing estrus
32
Q

When should insemination occur?

A

Ideally around 12 hours after start of standing estrus
Ovulation occurs around 24 hours, sperm have longer fertile life than egg so better they are already in the tract waiting

33
Q

Recommended elective waiting period. Why?

A

60 days or longer for high producing cows

Uterine involution takes 5-6 weeks, more cycles before AI better
Better conception rates, cow has better BC

34
Q

How to find non pregnant cows to rebreed them

A
  • blood serum test or milk test 28 d after AI
  • ultrasonography from 27 d after AI
  • palpation per rectum 35-45 d after AI
35
Q

Advantages to ultrasonography for pregnancy diagnosis

A
  • instant result
  • quick and accurate from 28-32 d
  • can confirm viability (heartbeat)
  • diagnose twins
36
Q

Why perform early pregnancy diagnosis*

A
  • identify open cows early (rebreed sooner)
  • reduce numbers of days open
  • reduce economic losses
  • help with culling decision
37
Q

Possible causes of embryonic losses*

A
  • poor CL/insufficient P4
  • weak embryonic signal
  • diet (high protein)
  • environment
  • trauma (early palpation)
  • twin pregnancies
  • infections
38
Q

Possible methods of reducing early embryonic losses

A
  • GnRH infection after AI
  • progesterone supplementation
  • good BC for breeding
  • early identification of twin pregnancies
39
Q

How does protein affect fertility

A

Increased intake of rumen degradable protein = lower fertility (metabolic residues (ammonia/urea) interfere w fertilization and embryo transport)

40
Q

Applications of ultrasonography

A
  • uterine infections
  • ovarian cysts
  • early pregnancy diagnosis
  • twins
  • sexing
41
Q

Applications of fetal sexing

A
  • influence sale price of bred animals (female fetus=more)
  • group bred heifers by fetal gender makes calving management easier
  • culling/selling decisions based on fetal gender
  • twins: distinguish same sex twins from freemartin
42
Q

How are modern cows physiologically different

A
  • calving to first ovulation longer
  • increase in abnormal estrous cycles, cystic ovaries, twinning rate
  • estrus beh less prominent, duration of estrus reduced
  • higher prod cows have lower conc of P4

AN SC 472 (13 decks)

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