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Theriogenology > Anestrous > Flashcards

Anestrous Flashcards

1
Q

What is anestrus?

A

A condition when a female does not exhibit estrous cycles.

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2
Q

What is the status of the ovaries during anestrus?

A

The ovaries are relatively inactive, with no ovulatory-sized follicles or corpora lutea present.

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3
Q

What are the two types of anestrus that can occur?

A

True anestrus (due to insufficient GnRH release) and apparent anestrus (due to failure to detect estrus or pregnancy).

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4
Q

How can true anestrus be prevented?

A

Through improved nutrition, removal of offspring to terminate lactation, or elimination of pathological conditions.

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5
Q

What is one way to eliminate apparent anestrus?

A

Improved estrus and pregnancy detection.

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6
Q

What are the 6 types of anestrus?

A

Congenital, nutritional. seasonal, gestational, lactational and pathological

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7
Q

What three things occur with congenital anestrus?

A

Free martins, ovarian aplasia, ovarian hypoplasia

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8
Q

What is a free martin?

A

A freemartin is a heifer born twin to bull; approximately
90% are sterile.

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9
Q

What causes freemartins?

A

Caused by a “chimeric” condition where haematopoetic cells mix in utero between the fetuses resulting in XX and XY cells present in a freemartin.

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10
Q

What are the effect of the factors leading to freemartins?

A
  • Partial expression of testicular determining factor from male Y chromosome inhibits the female gonad.
  • Mullerian inhibiting factor from the male cells prevents the Mullerian duct development, and so no uterus forms.
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11
Q

What is ovarian aplasia and how does it occur?

A
  • This is a rare condition when one or both ovaries are absent.
  • It appears when the gonadal ridge does not form correctly.
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12
Q

What is the best way to diagnose ovarian aplasia?

A

Palpation

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13
Q

What is ovarian hypoplasia and what causes it?

A
  • In ovarian hypoplasia, one or both ovaries are smaller than normal.
  • Caused by a single autosomal recessive gene.
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14
Q

What species is nutritional anestrus a problem and why?

A

Nutritional anestrus is the most common problem in beef cows. Producers often try to get by on as little feed as possible to their cows.

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15
Q

What is the best way to assure early return to cyclicity in beef cows?

A

Feeing pre-partum

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16
Q

What happens when you provide good nutrition ante-partum

A

the stress of
post-partum lactation produces a shorter duration of
negative energy balance.

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17
Q

What characterizes seasonal anestrus?

A

Seasonal anestrus is characterized by hypothalamic dormancy with regard to GnRH secretion (as in the
prepubertal female); GnRH pulsatility is low.

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18
Q

What needs to happen in the hypothalamus before the breeding season begins?

A

Before the breeding season begins, the hypothalamus must be able to release GnRH in sufficient amounts to elicit a response by the anterior pituitary.

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19
Q

Long day breeders vs short day breeders

A

Long-day breeders - mare, as the day length increases in the spring the mare begins to cycle and during the short days of the winter months, the mare is in anestrus

Short-day breeders - sheep, goats, elk, deer, begin to cycle during the short days of the fall. The duration of the breeding season varies among species and is determined by the duration of pregnancy.

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20
Q

What species dont experience lactational anestrus?

A

Mare and alpaca

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21
Q

What happens to cyclicity in sows during lactation?

A

Cyclicity is completely suppressed during lactation

22
Q

What happens to cyclicity in cows during lactation when calf is suckling?

A

In the suckled cow, cyclicity is delayed by as much as 60
days after parturition.

23
Q

What influences the duration of lactational anestrus in the cow?

A

The duration of lactational anestrus is influenced by the
degree of suckling in the cow.

24
Q

What promotes return to cyclicity vs prolong PP anestrus in cows with suckling calves?

A

Suckling sessions of two or less per day promote return
to cyclicity, while greater than two sessions per day tend
to cause prolonged post-partum anestrus.

25
Q

What are some examples of pathological anestrus?

A

Cystic ovarian dz, pyometra, ovarian atrophy, mummified fetus

26
Q

How does pyometra occur?

A

secondary infection as a result of hormonal changes in the female’s reproductive tract. Following estrus (heat), the hormone progesterone remains elevated for up to two months and causes the lining of the uterus to thicken in preparation for pregnancy. If
pregnancy does not occur for several consecutive estrus cycles, the uterine lining continues to increase in thickness until cysts form within the uterine tissues (cystic endometrial hyperplasia).

27
Q

When is pyometra most common?

A

may occur in any sexually intact young to middle-age dog, but most common in older dogs

28
Q

What creates an ideal environment for bacterial growth in pyometra cases?

A
  • The thickened, cystic lining secretes fluids that create an ideal environment for bacterial growth.
  • Uterine muscle cannot contract properly either due to thickening of the uterine wall or the high levels of the hormone progesterone. Bacteria that enters the uterus and accumulated cannot be expelled.
29
Q

What is luteolysis and when does it occur?

A
  • Luteolysis is physical and functional elimination, or
    disintegration (-lysis) of the corpus luteum.
  • It occurs during one-to-three day period at the end of luteal phase.
30
Q

What is the main hormone responsible for luteolysis?
And others?

A

The dominant hormone responsible for luteolysis is PGF2a produced by endometrium.

Other hormones controlling luteolysis are oxytocin (produced by CL?) and ovarian steroids.

31
Q

Difference of CL lifespan in intact uterus vs total uteroectomy vs partial uteroectomy contralateral vs partial uteroectomy ipsilateral?

A

In the presence of intact uterus
in ewes, life span of CL is ~15
days

With the total uteroectomy, the
lifespan of CL is similar to a
normal pregnancy (148 days)

Partial uteroectomy contralateral to CL will yield a lifespan similar to a normal cycle (~15 days)

Partial uteroectomy ipsilateral to CL will yield a lifespan longer than normal cycle (35 days)

32
Q

What is required for the lysis of the CL?

A

Uterus

33
Q

What doe the uterus control?

A

Controls luteolysis through local mechanisms

34
Q

How does PGF2alpha get from the uterus to the ovary

A
  • Vascular counter-current exchange mechanism.
  • A counter-current transport involves primarily arteries
    and veins in which blood flows in opposite direction to the adjacent vessels.
  • Utero-ovarian vein and ovarian artery lie in close
    association.
35
Q

Where is PGF2alpha produced?

A

PGF2a produced by endometrium is carried by uteroovarian
vein and is transferred by passive diffusion to
ovarian artery.

36
Q

Where are the receptors located for PGF2alpha?

A

Large luteal cells (on CL)

37
Q

___ P4 Receptor + ____ E2 receptor = ____ OX-R and ____ PG2alpha production

A

decreased, increased; high, high

38
Q

What is required to initiate timely synthesis of PgF2α?

A

Exposure to progesterone (P4) is required, leading to the accumulation of arachidonic acid and prostaglandin endoperoxidase.

39
Q

How does oxytocin affect PgF2α secretion?

A

Oxytocin stimulates pulsatile secretion of PgF2α, with 1 pulse every 6 hours leading to luteolysis.

40
Q

What effect does PgF2α have on blood vessels?

A

It causes vasoconstriction.

41
Q

Which immune cells are present in the corpus luteum (CL) during luteolysis?

A

Macrophages and lymphocytes.

42
Q

What is currently unclear regarding immune cells during luteolysis?

A

How these cells are attracted to the corpus luteum during luteolysis.

43
Q

What role do cytokines produced by immune cells play in luteolysis?

A

They induce the death of luteal cells by apoptosis.

44
Q

How is the final cleanup of luteal tissue performed?

A

By macrophages through phagocytosis.

45
Q

How often does estrus and ovulation occur in a normal cycling cow

A

21 days

46
Q

What happens if you give a single PGF2aplha injection between day 0-6 in the cycle?

A

luteolysis will not occur because
CL must reach certain stage of
development before it is sensitive to PGF2a.

47
Q

What happens if you give a single PGF2aplha injection between day 6-17 in the cycle?

A

If PGF2a is injected on day 6-17, luteolysis will occur. Progesterone will drop and the animal will return to estrus in about 3 days.

48
Q

Difference in when ovulation occurs after injection for follicles that are aged vs in the growing phase?

A

Animals receiving PGF2a when the dominant follicle is in the growing phase will ovulate within 3-4 days, whereas animals with aged dominant follicles (late static or regressing phase) will require 5–7 days before a new follicle can ovulate.

49
Q

What does the timing of the PGF2alpha injection determine in cows?

A

timing of the PGF2a injection determines the interval to ovulation in cows.

50
Q

Why does timing of injection determine interval to ovulation in cows?

A

Bc the emergence of a new follicular wave is associated with the loss of ovulatory capacity by the dominant follicle of a previous wave.

51
Q

What occurs when there is maternal recognition of pregnancy?

A
  • A mechanism whereby the regression of CL is prevented early in gestation
  • Preventing the decline in luteotropic support (primates)
  • Protecting the CL from exposure to luteolysin PgF2a (domestic animals)

Theriogenology (12 decks)

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