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Y4 FA - Reproduction > Bovine Oestrus Cycle > Flashcards

Bovine Oestrus Cycle Flashcards

1
Q

Which oestrus related hormones are produced in the pituitary gland?

A

FSH
LH

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2
Q

What are the roles of FSH and LH?

A

FSH – stimulates follicle development in the ovary
LH – causes the dominant follicle to ovulate

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3
Q

Where is oestrogen produced?

A

From the follicle

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4
Q

What are the functions of oestrogen?

A

Stops further FSH production
Dictates signs of heat being shown

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5
Q

Describe once happens once a follicle ovulates?

A

Follicle bursts and the egg is released
Corpus luteum grows
Corpus luteum produces progesterone which prepares the uterus for pregnancy

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6
Q

Which hormone causes the pituitary gland to produce LH and FSH?

A

GnRH

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7
Q

Describe the ovaries post-ovulation

A

Large follicle has gone
Left with small residual follicles
Ovaries are small

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8
Q

Name the gland used in some species to influence reproduction that is involved in seasonality

A

Pineal gland

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9
Q

Where is GnRH released from?

A

The hypothalamus

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10
Q

Which hormones produced in the ovaries have +ve and -ve feedback on the brain?

A

Oestradiol
Inhibin

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11
Q

Describe the stages follicles go through before ovulation

A
  • Primordial follicular pool
  • Primary follicles initiated for growth
  • Antrum formation
  • Recruitment: some atresia of follicles occurring
  • Selection and dominance of follicles: more atresia
  • Single dominant follicle that ovulates
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12
Q

Name the 4 stages of a cows cycle

A

Oestrus
Metoestrus
Dioestrus
Proestrus

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13
Q

The levels of progesterone are high during which phase of the cycle?

A

Dioestrus

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14
Q

From ovulation, how many days does it take for the CL to reach maturity?

A

6 days - get a gradual increase in progesterone following ovulation

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15
Q

From day 6, for how many days is progesterone secreted at maximal levels?

A

Until around day 16 - then luteolysis occurs and the CL is destroyed

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16
Q

Describe the cycle following luteolysis

A

Sudden progesterone drop ready for the next ovulation

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17
Q

Describe follicular waves throughout the cycle

A

During the period of dioestrus (high progesterone levels) follicles do continue to develop in waves; however, hormone interactions prevent ovulation.

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18
Q

How does a high yield influence a cows cycle?

A

They are likely to have less follicular waves per cycle

19
Q

Compare the return to cyclicity in dairy vs beef cows

A

Dairy cows will return to cyclicity very soon post calving but beef cows can be up to 3 months before cyclicity returns

20
Q

How does the emergency of the 1st follicular wave (days post partum) differ in dairy vs beef cattle?

A

It doesn’t, tends to be between 5-10d post calving

21
Q

How does the % of cows that ovulate the first dominant follicle differ in dairy vs beef cattle?

A

Dairy = 50-80%
Beef = 20-35%

22
Q

How does the days to 1st oestrus differ in dairy vs beef cattle?

A

Dairy = 25-45
Beef = 30-130
- Nature of the first ovulation is silent in both

23
Q

Success of AI depends on which two factors?

A

Use of proven/fertile sires
Reliable oestrus detection

24
Q

List the signs of oestrus detection - describe which cow is in oestrus when these signs take place

A
  • Sniffing of the vulva: cow sniffing the vulva is in oestrus
  • Chin resting: both cows involved are in oestrus
  • Licking: both cows
  • Bunting: both cows
  • Mounting head to head: cow mounting is in oestrus
25
Q

Which sign has the shorting duration during heat?

A

Standing to the mounted

26
Q

Which oestrus behaviours have the highest occurance?

A

Sniffing
Chin resting
Mounting

27
Q

How can steps be used to monitor oestrus

A

Usually an increase in steps/hr when in oestrus

28
Q

How long is the duration of standing heat?

A

Between 3-15hrs
High % only for 3 hours so easy to miss

29
Q

What is the am/pm rule?

A

If you see a how standing to be mounted in the am, then serve in the pm. And vice versa

30
Q

If more cows are in heat, what does this influence?

A

How obvious the signs are

31
Q

Describe the use of mount detectors

A
  • Paint / chalk or Kamar/Ambic
  • A cow is detected only when stands to be mounted - not all animals show standing heat
  • Threshold is important
  • Easy to use, but maintancence can be time consuming
32
Q

Describe some other possible aids for oestrus detection/monitoring

A
  • Record keeping
  • Teaser animals
  • Chinballs
  • Monitors milk progesterone - everyday for every cow
  • Activity monitors
33
Q

Describe ‘heattime’ as a method of oestrus monitoring

A
  • Basal activity of each cow is calculated
  • If her activity increases beyond the mean +5 S.D then it is noted that she is showing oestrus behaviour
  • Same efficiency of farm staff (but still around 40% of heats not detected)
  • Ideally used in combination
34
Q

How many sperm are in the following:
1. ejaculate
2. in a normal straw of conventional semen
3. in a straw of sex sorted semen

A
  1. Billions
  2. 15-20 million
  3. 1 million
35
Q

Where are sperm deposited?

A

in the body of the uterus or into one horn

36
Q

Describe the AI routine

A
  • Thaw @ 37 deg. for 40 seconds
  • Dry thoroughly
  • Load gun, snip off end of straw
  • Disposable sheath
  • Keep warm
  • Chilling once thawed bad!
  • Thaw one at a time!
  • Get AI company to test some straws or do yourself
37
Q

Things to consider if reduced pregnancy rates following AI =?

A
  • Has flask become empty, and sperm thawed then refrozen?
  • Have they used fingers rather than tweezers
38
Q

Name the stages of initial oocyte and embryonic development

A
  • First cleavage
  • Embryonic genome activation
  • Morula compaction
  • Blastocyst formation
39
Q

Which hormone is crucial for embryo growth?

A

Progesterone

40
Q

Describe how luteolysis or maternal recognition of pregnancy occur

A

OT-R = oxytocin receptors – in the endometrium
- Prostaglandins destroy the CL if there is no embryo implantation
- If there is maternal recognition of pregnancy progesterone production continues and OT-Rs don’t develop. There is minimal PGF2a and there is no lysis of the CL

41
Q

In a bovine pregnancy when is it visible on a scan/palpation

A

About day 27-28

42
Q

The level of which hormone build up towards the end of the pregnancy?

A

Oestrogen

43
Q

Calving is controlled by?

A

The calf

44
Q

Which hormone produced by the calf triggers parturition

A

Cortisol

Y4 FA - Reproduction (10 decks)

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