Reproduction & neonatology

In a spontaneous ouvulator, LHis autoatically produced. In an induced ovulator, what has to occur first befre LH production and ovulation occur?

Coitus

For most species, the luteal phase of non-pregnancy s about 16d after ovulation. What determines the length of the luteal phase?

The lifespan of the corpus luteum

What causes the lysis of the corpus luteum if the female is not pregnant?

Progesterone

Pregnancy results in lengthening of the luteal phase as there is a block to the nomral process of corpus luteum luteolysis. In most species, progesterone is elevated for the duration of pregnancy. Where can this progesterone come from?

From the ovary or frm the placenta in late pregnancy

Cats are induced ovulators. This means that progesteorne doesn’t rise unless what occurs?

Ovulation as a result of coitus

What are the characteristics of the female cats cycle if ovulation does NOT occur?

Waves of increasing and then decreasing oestrogen

What breeding pattern does the bitch have?

Non-seasonal mono oestrus

How long is the typical luteal phase in the bitch?

70 days

Why does the luteal phase in the bitch start before ovulation?

Due to pre-ovulatory luteinisation

Porlactin supports the production of progestrone from the corpus luteum. So what happens if you remove prolactin?

You remove the support for the progesterone and it will drop

Every non pregnant bitch has elevations in progesterona and prolactin. This can results in signs of?

Progesterone:

• Mammary enlargement

• Potential for milk secretion

Elevated prolactin:

• Milk production

• Behavioural changes typical of pregnancy

When does puberty occur in the bitch?

Variable

• mean: 9 months

• Vares between 6-24mo

• Some bitches 24-30mo

• WHEN BITCH REACHES 80% OF ADULT BODY WEIGT

When is peak fertility in the bitch?

At approx 2yo and generally maintained until 6-7yo

Describe the average cycle of the bitch

Interval between onset of pro-oetrus = 7months

• Pro-oestrus = 10d

• Oestrus = 10d

• Luteal phase = 60d

For the average bitch, how long is anoestrus?

4.5months

Anoetrus is the period between the end of the luteal phase and the onset of what?

The subsequent return to pro-oetrus

The minimum period that anoestrus lasts is 7 weeks but it usually averages 18-20w. There are changes in the pituitary gland’s responsiveness as anoestrus progresses ad approximately how ay days before ovulation can follilces be detected in thhe ovaries?

60

What hormonal changes tend to occur in late anoestrus?

Increased LHpulse frequency accompanied by FSH pulses and a less prominent increase in mean FSH concentrations.

Proestrus is associated with the stimulation of follicle development by FSH and LH and the subsequent secretion of what hormone from the granulosa cells of the follicle?

Oestrogen

What changes to the reproductive tract are seen in pro-oestrus and are related to increasing levels of oestrogen?

Increasing vascuarity and oedema - swelling of internal and external reproductive tract, mucosal capillaries leak at endothelial junction = passage of blood and plasma into the uterine lumen

Increased activity of glandular epithelium

What are the clinical signs of pro-oestrus?

Enlargement and redenning of the vulval lips

Serosanginous vulva discharge

Increased attentiveness to male dogs, ++U marking, tendency to roam

What changes occur to the vaginal epithelium in pro-oestrus?

Enlargement & swelling of vaginal epithelial folds

Epithelial cell proliferation induced by oestrogen. Mucosa changes from a cuboid epithelium to a stratified squamous epithelium

Elevations in LH and FSH are crucial events for stimulating follicle growth. However, as follicles mature they produce what hormone which is a selective inhibitor of FSH secretion?

Inhibin

What does FSH do during pro-oestrus?

Causes follicle development &stimulates follicular growth

Equipping of cells for conversion into CL after ovulation

What happens to oestrogen levels during oestrus?

There is an initial increase which then declines prior to ovulation

What happens to LH&FSH during pro-oestrus?

There is suppression of LH &FSH due to negative feedback from oestradiol &inhibin respectively.

How long after oestogen declining does the pre-ovulatory LH surge begin?

1d

What changes occur to the vaginal wall during oestrus?

A loss of oedema, resulting wrinkling and crenulation

What hormonal changes ar erequired to facilitate full exprsesion of behavioural oestrus?

Declining oestrogen and rising progesterone

What is ovulation caused by?

A surge release of LH that occurs a few days after peak oestrogen concs are reached

Luteinisation of the follicle wall occurs prior to ovulation and there is a significant increase of what hormone?

Progesterone

THe LH surge stimulates ovulation but also shifts steroid production in granulosa cells from oestrogen to what hormone to ohelp the follicle develop into a corpus luteum?

Progesterone

Does the bitch tend to have single or multiple ovulations?

Multiple

Whycan’t oocytes be fertilised immediately after ovulation in the dog?

Because they are immature

What events need to take place in order for he primary oocyte to form the secondary oocyte?

1. Extrusion of the first polar body

2. Completion of the first meiotic division

How long does it take for the primary oocyte to turn into the secondary oocyte?

48-60h

Where does maturation of the primary follicle occur?

In the distal oviduct

oocytes Remain viable within the reproductive tract for many days after they have become fertilisable when do they start to undergo degeneration after ovulation?

9-10d

The fertilisation period is the time when oocytes Are available to be fertilised in the bitch when does this period commence And finish?

It commences two days after ovulation and extends until approximately five days after ovulation

Why does max fertility decline over the next few days after the first period?

Due to degeneration of the oocytes And closure of the cervix which prevents sperm entering the female reproductive tract

why do you tend to get small litter size if the bitch has been impregnated after the fertilisation period?

By fertilisation of aging oocytes

Why does breeding prior to the fertilisation period commonly result in pregnancy?

because the sperm can survive in a female reproductive tract

The first Eilidh period is defined as the time during which a breeding could result in conception the fertile period therefore includes the fertilisation period but Proceeds it by up to how many days before ovulation?

6d

In the bitch how long after ovulation can you have a standing oestrus behaviour?

7 days

What effect does progesterone have in the luteal phase?

Alters the characteristics of mucosal secretions, Decrease smooth muscle excitability and is thought to slow the passage of ova in the uterine tubes. It closes the cervix and prepares the uterine environment to facilitate support of the embryo

What are the luteotrophic factors In the luteal phase?

Prolactin LH And progesterone

When do prolactin and LH have luteotrophic action from?

Week two

At what point are the LH and prolactin required as luteotrophic Hormones?

From day 25

Administration of prolactin inhibitors and LH suppressor will terminate the luteal phase after what date in both pregnant and non-pregnant dogs?

D25

Prostaglandin is a luteotrophic hormone TRUE OR FALSE

False, It is a luteolytic Hormone

In pregnancy progesterone is produced solely from what throughout the duration of the pregnancy?

The corpus luteum

Why does inhibition or antagonism of prolactin secretion in the second half of pregnancy result in a termination of the luteal phase and termination of pregnancy?

Because during the second half of the new phase, the progesterone concentration starts to decline But there is a con commitment increase in plasma collecting concentration secreted by the pituitary. It supports the corpus luteum and tends to maintain an elevated progesterone concentration.

For what period of time does the corpus luteum Appear to be almost Autonomous?

For the first 14 days after ovulation

The hormone relaxing is the only known pregnancy specific hormone in the bitch. It is present in plasma 25 days after ovulation and Pete values are reached approximately date 50 and appears likely to be produced entirely from what?

The placenta are there some evidence to demonstrate higher values in bitches with larger size because of the increase volume of the placenta

What Does relaxin Do?

To soften the fibrous connective tissue prior to birth

Why can a normocytic / normochromic Anaemia occurred during pregnancy?

Because of a pregnancy specific increase in blood volume that is associated with a significant reduction in the percentage Paxel volume

What happens to Oestrogen during the phase?

Tend to increase during the luteal phase

What are the clinical signs of a phantom pregnancy?

Anorexia, nervousness, aggression nest making nursing lactation and occasionally false parturition

How can you treat a phantom pregnancy?

Using prolactin inhibitors such as Cabergoline and Bromocriptine For 5 to 7 days

What is considered to be the final trigger for the initiation of partition in The bitch?

A precipitous decline in plasma progesterone

What does a loss of progesterone cause in parturition?

It removes the progesterone block to myometrial contractions and results in increased basil uterine contractions as well as increased reproductive tract secretions

What is prostaglandin F metabolite?

This originates from the feto-Placental unit and increase concentrations are found during both the prepartum luteolysis and parturition

Why is the luteal Phase in the non-pregnant bitch longer than in the pregnant bitch?

Because there is no increase in PG FM plasma progesterone concentrations decline slowly

What causes an increase in prolactin secretion similar to values in late pregnancy during lactation?

sucking by the neonates

How long does lactation typically last for in the bitch?

Six weeks

What is the breeding pattern for the queen?

Polyoestrus seasonal long day breeding pattern

When does the first oestrus tend to occur in the queen?

Between 4-12 months of age

What factors influence the onset of puberty?

Breed - Shorthairs reach puberty earlier than longhair, Burmese reach puberty early (4mo) while Persians reach puberty late (12mo)

The time of year of their birth - summer/autumn born kittens will reach puberty at their first spring (5-6m) but spring born kittens tend to reach puberty at 12 months at the subsequent spring

Body condition - 2.5 to 3kg

Social environment - free ranging cats earlier than owned cats

Plane of nutrition

When does peak fertility tend to occur in the queen?

2-8yo

The cat is a seasonal long day breeder. When is anoestrus typically observed?

Over 3-4months of winter

What regulates melatonin which regulates anoestrus?

The pineal gland

What is the average interval from one ovulation to the next during the breeding season?

14-21d

What is the cycle of the non-mated queen split into?

Interoesteus (8-15d)

Pro oestrus (1d)

Oestrus (2-6d)

How long does the non-pregnant luteal phase last in the queen?

25-45 days

How long is the pregnant luteal phase in the queen?

65 days

Queens will display oestrus behaviour every 2-3w unless what factors have occurred?

• out of breeding season

• Ovulation has occurred

• Depot progesterones have been given

• Significant systemic illness

• Neutered

Why do non mated cats not enter the luteal phase?

No ovulation and no corpus luteum is formed

Why is it important that a female cat is mated frequently?

Because it is needed to stimulate higher levels of LH which is required for ovulation

Anoestrus is the absence of cycling activity which occurs naturally in periods of short days associated with increased secretion of what?

Melatonin

Artificial lighting can terminate anoestrus though generally how many months of supplementary lighting are required?

2 months

Aside from artificial lighting, what else can bring a cat of our anoestrus?

Tom cats

Cats usually are in anoestrus when they are lactating. When do they tend to return to oestrus?

Some cats can come into oestrus during the second third or fourth week during lactation. Otherwise 2-8w after weaning

What is inter oestrus?

The period between one oestrus and the next in queens that have not ovulated

During inter oestrus, oestrogen levels are high or low?

Low and no sexual behaviour is observed

Pro-oestrus and oestrus are associated with stimulation of follicle development by what?

LH and FSH

What changes can be seen the the vulva in oestrus?

Slight reddening and swelling of the vulval lips

What clinical signs are seen when a cat is in oestrus?

Increased activity

Vocalisation

Howling

Reduced appetite

Spinal lordosis

What factors can affect a cat displaying behavioural oestrus or “silent heat”?

Nervous cats or low end of the social scale

Inexperience

Distraction

Male preference

The queen is an induced ovulator, what does this mean?

Mechanical stimulation of the vagina is required for neuronal triggering in the hypothalamus. Which results in GnRH release which induced LH release

How soon after mating does LH release begin?

A few minutes, with a peak LH being reached 2-4 hours later

Why does ovulation not always occur when there has only been one mating?

The magnitude of the LH surge is related to the day the queen is mated, quality of the mating, intervals and total number of matings. The LH surge is perceived to be of greater magnitude and longer duration when multiple matings occur in a short period

How many matings and over what period tend to produce the optimal amount of LH release?

3-4 matings over 2-4h

Why can mating later in oestrus require fewer matings to induce ovulation?

Due to plasma oestrogen concentrations allowing the anterior pituitary to respond better to copulatory stimulation and causing a great magnitude in LH surge

What can cause spontaneous ovulation?

• queens that are frequently groomed or those that self groom

• Older queens

• Those in presence of a Tom cat

True or false: oocytes are ovulated after first extrusion of the polar body which means that they can be fertilised immediately after ovulation in the queen

True

Where does fertilisation occur in the queen?

In the oviduct

After a non ovulating cycle, the queen returns to inter oestrus with basal plasma oestrogen concentrations for how many days before the growth of the next follicular wave?

8-15 d

What happens in cats where there is overlapping of follicle waves?

There is either no or a very small gap between the observed oestrus behaviour because there is both:

• decreasing oestrogen produced by atretic follicles

• Increasing oestrogen produced by the next follicle wave

What breeds tend to have overlapping of follicle waves?

Oriental breeds