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REPRO > Artificial reproductive technology 1 > Flashcards

Artificial reproductive technology 1 Flashcards

1
Q

Define artificial insemination

A

Placing semen into the female reproductive tract

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2
Q

What kind of semen can be used for AI?

A
  • Fresh
  • Fresh-extended
  • Extended-chilled
  • Extended-frozen-thawed
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3
Q

What is an extender in AI?

A

A formulation that keeps sperm alive over a longer period of time

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4
Q

What are the benefits of AI?

A
  • Allows greater access to superior genetics and maximises genetic improvement
  • Reduces mating costs and risks
  • controls reproductive disease
  • Allows use of dead or injured sires (if collected before death or injuery)
  • Can be used as part of embryo transfer regimes
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5
Q

When might semen analysis be undertaken?

A
  • Lowered fertility suspected
  • Abnormal sexual behaviour
  • Before sale
  • Before breeding season
  • If pathogenic infection is suspected (to enable culture/isolation of pathogens)
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6
Q

What information can be gained from semen analysis?

A
  • Fertilising potential of the ejaculate
  • Appearance
  • Motility
  • Live:dead ratio
  • Morphology
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7
Q

Why is semen analysis a poor discrimiinator between moderate and high fertility of an ejaculate?

A
  • Would require sperm function tests
  • Not done routinely
  • Temp, pH, ATP content, penetration of cervical mucus
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8
Q

Outline the features of a gross abnormality assessment of semen

A
  • Colour compared to normal
  • Normal fractionation
  • Normal gel component
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9
Q

What is the normal appearance of the sperm rich fraction of semen?

A

Creamy with some density

- Can be graded 1-5 and used to estimate sperm density

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10
Q

What is important when using a semen sample to assess motility?

A
  • Spermatozoa very sensitive to cooling
  • Must be maintained around body temperature (37)
  • slides and dilutents must be warmed
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11
Q

What are the 2 methods of motility assessment?

A
  • Subjective assessment (standard)

- Objective assessment (computer aided)

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12
Q

Describe a subjective assessment of sperm motility

A
  • Placed on warmed slide on heated stage, evaluate immediately
  • Estimate percentage of sperm with different motility types
  • need progressive (forward) movement
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13
Q

What is the difference between motility and progression?

A
  • Motility can be good i.e. lots are moving in one way or another
  • But may have poor progression i.e. very few are moving forwards
  • Poor progression means lower fertilising ability
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14
Q

Describe the objective assessment of sperm motility

A
  • Computer Assisted Sperm Evaluation

- Measures mean sperm velocity, mean sperm linearity, lateral head deviation, mean curvilinear velocity

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15
Q

How can sperm viability and morphology be assessed?

A
  • Staining of sperm with dyes and observation under phase microscope
  • Observation of fixed sperm by differential interference contrast (DIC)
  • Either need to highlight the sperm by background staining, or stain the sperm themselves
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16
Q

What is differential interference contrast?

A
  • A method of assessing sperm viability and morphology
  • Objectives mounted in microscope
  • Observation of fixed sperm with contrast
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17
Q

How is membrane function of a sperm assessed?

A
  • Staining
  • Using nigrosin-eosin staining
  • Poor membrane will be stained by eosin and will appear pink
  • Good membrane will exclude eosin and appear pink
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18
Q

How can fertility of sperm be assessed?

A
  • Not by conventional evaluation
  • Rely on sufficient number of normal and motile sperm to assume normal fertility
  • Can do fertilisation assays (not routine)
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19
Q

Name the fertilisation assays for sperm

A
  • Zona binding test

- Oocyte penetration test

20
Q

List the methods for semen collection.

A
  • Teasing followed by one of these below
  • Artificial vagina with teaser or dummer female
  • Teaser or dummy female and manual manipulation of penis
  • Electro-ejaculation
21
Q

What is the semen collection method usually used in bulls and stallions?

A

Artificial vagina with teaser or dummer female

22
Q

What is the semen collection method usually used in boars and dogs?

A

Teaser or dummer female with manual manipulation of the penis

23
Q

What is the semen collection method commonly used in rams?

A
  • Teaser or dummy female with artificial vagina

- Electroejaculation

24
Q

How is bull semen usually stored?

A

Freezing

25
Q

How is ram semen usually stored?

A

Frozen or fresh

26
Q

How is boar semen usually stored?

A
  • Poor freezing ability

- Extended at ambient temperature

27
Q

How is stallion semen usually stored?

A
  • Poor freezing outcome and significant individual variation
  • Fresh, chilled
  • Frozen in straws
28
Q

How is dog semen usually stored?

A
  • Poor freezing outcome and significant individual variation
  • Chilled
  • Frozen
  • Rare
29
Q

What are the 3 types of sperm abnomality than can occur?

A
  • Primary: defect of spermatogenesis
  • Secondary: epididymis (maturation)
  • Tertiary: post-ejaculation (trauma)
30
Q

Give examples of commonly seen sperm abnormalities

A
  • Pyriform head
  • Knobbed acrosome
  • detached or swollen acrosome
  • Nuclear vacuoles
  • Detached heads
  • Distal midpiece reflex (kink in tail)
  • Looped tail
  • Coiled tail
  • Cytoplasmic droplets
31
Q

What species have fractionated semen?

A
  • Stallion
  • Boar
  • Dog
32
Q

How can semen be preserved?

A
  • Fresh-extended (room temp)
  • Diluted/cooled (5degreesC)
  • Diluted/frozen (-196degrees C)
33
Q

What is the process for storing semen as diluted/frozen?

A

Frozen using liquid nitrogen

34
Q

What is the life span of semen that has been fresh-extended at room temperature?

A

Up to 8 hours

35
Q

What is the life span of diluted/cooled (5degreesC) semen?

A

Up to 4 days for most species, 10 days for boars

36
Q

What is the life span of diluted/frozen (-196degreesC) semen?

A

Indefinite - only thawed when eneded, can be frozen forever and deep freezing preserves structure and viability

37
Q

How do extenders carry out their function?

A
  • Protect sperm during cooling/freezing/warming
  • Supply an energy (glucose and protein) source to sperm
  • maintain pH, osmolarity and ionic strength (contain bicarb as buffer)
  • Prevent bacterial growth
38
Q

What factors are important in semen preservation?

A
  • Protective agents (milk or egg protein/glycerol)
  • sugars
  • pH, osmolarity, ionic strength
  • Antibacterial agents
39
Q

Describe freeze-thawing of semen

A
  • Can cause significant sperm damage
  • Additional cryoprotectants required
  • Controlled freezing rate and thawing rate required
40
Q

Give examples of cryoprotectants

A
  • Penetrating (glycerol, DMSO)

- Non-penetrating (proteins, large molecular weight sugars)

41
Q

Describe what happens to the spermatocytes if the freezing rate is slow enough and permeable to water

A
  • During freezing, water leaves cell which progressively dehydrates
  • Small ice crystals form inside cell
  • On thawing, ice crystals melt and cell rehydrates and is functional
42
Q

Describe what happens to spermatocytes if the freezing rate is too quick, or the cell is impermeable to water

A
  • During freezing, cell does not dehydrate, large ice crystal s form inside cell
  • Cell is damaged
  • On thawing, the cell is non-functional
43
Q

Describe what happens to spermatocytes if the freezing rate is too slow

A
  • During freezing, cells dehydrate and solute concentration increases
  • Solutes tend to precipitate
  • Cells shrink beyong minimum compatible with survival
  • Cell is damaged
  • On thawing is non-functional
44
Q

Describe sperm counting using a haemocytometer

A
  • Mutliply semen volume by sperm concentration
  • Place semen into haemocytometer coutning chamber after dilution
  • Count central square of counting chamber, by counting the 4 corner squares and the middle square of this
  • Multiply by 5 to get average, then by the volume of the counting chamber, then by the dilution factor
45
Q

What is semen sexing?

A
  • Separation of sperm based on DNA content in order to determine/choose whether the conceptus will be female or male
46
Q

What is the significace of semen sexing?

A

Economic value e.g. if cows are to produce milk or meat

47
Q

How is semen sexing carried out?

A
  • X chromosomes have more DNA than Y
  • X larger
  • Separate by labelling live sperm with DNA fluorescent dye and sorting by flow cytometry
  • More fluorescence from X, sorted into different containers

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