Seasonality, detecting and manipulating oestrus

what type of seasonality does a cow have

• she doesn’t, she is polyoestrus all year round

what occurs in the mare after her period of anoestrus?

• prolonged oestrus

how many cycles do we expect a mare to have each year?

• 9/10

how many cycles do we expect a ewe to have each year?

• 7

what occurs in a ewe after her period of anoestrus?

• silent oestrus

what are 4 seasonality controlling factors

1. photoperiod

2. melatonin

3. temperature

4. nutrition

what does melatonin directly affect?

• HPO axis

describe how a short day breeder returns to cyclicity after anoestrus

• increasing melatonin

• increased GnRH synthesis

• increased FSH, then LH

describe what happens to long day breeders to return back to cyclicity after anoestrus

• decreasing melatonin

• increasing plane of nutrition

• increased GnRH synthesis

describe what happens in the transition period in the mare

• increasing GnRH

• increasing FSH but NOT LH

• initiation of antral folliculogenesis but not to a good enough standard

• this casues irregular oestrus

• gradually there’s an increase in steroidogenic competence

• increased LH

• ovulation

• normal cycling

how long does the transition period take after oestrus in a mare

• 50-60 day

what do we call the follicles during the transition period?

• transition follicles

what are 2 things we can do to counter the seasonality of horses

1. shuttle stallions b/w hemispheres (can do females but less effective)

2. artificial change to the photoperiod

what are 4 hormones we can use to manipulate seasonality?

1. melatonin

2. GnRH

3. ECG

4. progesterone + ECG

what is ECG

• equine chorionic gonadotrophin

what does ECg affect?

• FSH/LH activity

• directly stimulates the ovary

if we have ewes in mid-august who we want to bring into sesason earlier, what hormones could we use for this?

• progesterone + ECG

which species do we mainly use melatonin on?

• sheep and goats

how would we describe the oestrus that occurs after the anoestrus period for a mare?

• erratic and irregular

describe what takes place in metoestrus

• uterus is prepared for pregnancy

• oestrus behaviour is inhibited

• LH surge (not tonic) is blocked

describe what the small peak of FSH causes

• antral follicle development is stimulated, selection of a dominant follicle occurs

describes what happens after dioestrus if the animal isn’t pregnant

• uterine PGF2a → luteolysis → reduced progesterone → increased oestradiol from ovulatory follicle inducing oestrus

when does the ovulation occur in a cow?

• 24 hours after LH surge - 12 hours after the end of oestrus

when should we mate a cow with an ideal oestrus cycle?

• one day prior to ovulation

why should we mate cows, ideally one day before ovulation?

• oocytes age if not fertilised and usually can’t be fertilised after 24hrs post ovulation

how long before ovulation should we perform AI

• 6-12 hours prior - the same day oestrus behaviour has been observed

what is challenging about timing mating/AI for cows

• detecting oestrus as there’s only 5-18 hours when she is in this period

is detecting/timing oestrus an issue with ewes?

• no as they’re mated throughout oestrus by a ram

what are 2 issues with mating ewes

• ram:ewe ratio

  • identification of mated ewes

when do we perform AI in ewes?

• 12 hours

When do we perform mating/AI for sows?

• day after onset of standing oestrus

how many inseminations do we typically use for sows?

• two

what is the normal practice of mating a mare?

• tease daily

• breed throughout the period

• monitor ovaries with ultrasound

what can we use to be more accurate with mating bitches?

• vaginal cytology

• plasma progesterone measurement

State 6 symtpoms of oestrus 2-24 hours before coming into oestrus in cows

• reduced milk yield

• brawling

• restlesness

• chin pressing

• swelling of vulva

• mucous discharge

state 4 clinical signs of standing heat in cows

1. stands to be mounted

2. mounts other cows

3. swelling of vulva

4. mucous discharge

state what clinical sign we see going out of heat in cows

• bloody discharge - not menstruation!

what are 3 ways to detect oeestrus in cows

1. examine >4 x per day for >30 mins

2. classic detection aids

3. remote/electronic aids

what can we detect in plasma/milk to determine oestrus?

• progesterone

what can we detect in ultrasonography to confirm oestrus in a cow

• a large dominant follicle in absence of a CL

state 7 factors that might inhibit oestrus behaviour

1. hard slippery floor

2. high environmental temperature

3. high milk yield

4. overcrowding

5. recent mixing/stress

6. lameness

7. feeding

what medicine can we use to synchronise ovulation

• ovsynch - GnRH and PGF2alpha

why use ovsynch

• remove need to oestrus detection

• reduce time from calving to re-conceiving

state 3 signs of oestrus in the ewe

1. restlessness

2. stands for the ram

3. vulva

what are 2 detection methods of oestrus in the ewe

1. vasectomised ram with raddle

2. synchronisation protocols

what is WOI?

• weaning to oestrus interval

what are 5 typical signs of oestrus in the sow

1. stands to be mounted

2. vulval reddening, swelling + congestion before oestrus

3. seeks boar, pacing, searching, grunting

4. stands for boar

5. responds to pheromones

why is it key we know when to put the stallion in with the mare

• if we time it wrong it can lead to damage of the stallion

what are 5 signs of oestrus in the mare?

1. oedematous vulva with mucoid discharge

2. elevated tail, leaning hindquarters towards stallion

3. spreading hindlegs

4. repeated exposure of clitoris - ‘‘winking’’

5. ‘‘flehmen’’ response in stallion

what size of large follicle confirms oestrus in a mare?

• >20mm

describe pro-oestrus in the bitch

1. very long

2. bitch is attractive but won’t allow mating

3. vulval swelling

4. serosanguinous discharge

describe signs of oestrus in the bitch

• standing to be mated

• deviation of the tail

• discharge is paler

• vulval oedema is reduced

state 2 clinical methods of detecting oestrus in the bitch

• vaginal epithelial cells

• plasma progesterone concentrations

what type of ovulator is a queen

• induced

what does the queen require for oestrus?

• continuous mating to trigger the surge centre for LH surge before oestrus

state 7 signs of oestrus in the queen

1. increased vocalisation

2. increased activity

3. seek the tom

4. slight mucoid vulval discharge

5. extending hindlegs, demonstrating lordosis

6. tail is erect and to one side

7. lowers front quarters for mating

describe 3 occasions where anoestrus occurs

1. during lactation/present offspring

2. seasonality

3. monoestrus breeders

what are 4 pathological occasions that anoestrus occurs?

1. metabolic stress

2. heat stress

3. cystic ovarian disorders

4. inactive ovarian activity

what is a silent oestrus

• an oestrus with limited signs of oestrus

when does a silent oestrus typically occurs?

• first oestrus after seasonal anoestrus/parturition

what 3 things occur (or don’t occur) for anoestrus to take place

1. no progesterone priming brain centres

2. no progesterone fall to trigger oestrogen receptor expression in the brain

3. no sudden oestradiol release

when does silent oestrus take place in dairy cows?

• first ovulation post-partum typically

what state are dairy cows in which increases their chance of silent oestrus?

• severe negative energy balance

what are 2 potential solutions to preventing silent oestrus in cows

1. ovsynch

2. profiling progesterone levels in milk

describe what takes place in the follicular pahse of a typical 21 day oestrus

• increasing E2

• this triggers GnRH relsease → LH surge → ovulation

describe what takes place in the luteal phase of a typical ‘21’ day oestrus cycle

• Cl develops causing increasing progesterone levels until fully mature with elevated P4

what terminatees the luteal phase?

• luteolysis

describe polyoestruc cyclicity

• the cycle will repeat itself every number of days, beginning with ovulation (folliclar phase) and ending with luteolysis (end of luteal phase) triggering a new ovulation.

what doesn’t occur in animals, which occurs in humans?

• menstruation

how does pregnancy affect cyclicity?

• pregnancy expands the luteal phase and suppresses the return to oestrus, therefore having no cycles whilst gestating

describe the cyclicity of the bitch

1. non-seasonal

2. monoestrus

3. spontaneous ovulator

how long is the anoestrus period in a bitch?

• around 7 months

describe the hormonal changes in the bitch during pro-oestrus + oestrus

• oestradiol increasing dramatically

  • this will trigger an LH surge

  • ovulation occurs

describe the hormonal changes during monoestrus in the bitch

• prolonged period of monoestrus with an extended decline in progesterone levels which leads into a period of anoestrus

how is the oocyte less mature in dogs than other species?

• the dog oocyte arrests in meiosis I compared to meiosis II

what hormonal change is required for parturition?

• a sudden decrease in progesterone levels

compare the progesterone levels of a pregnant vs non-pregnant bitch

• progesterone is higher in the pregnant dog from day 21

• rapid fall in progesterone at parturition which doesn’t occur in the bitch

what influence does prolactin have on progesterone in the cycle of a bitch when pregnant?

• elevated prolactin secretion

• maintains elevated progesterone concentrations by stimulating the CL

• the placenta contributes

is there an increase in prolactin in the non-pregnant bitch?

• yes, although less significant than in the pregnant bitch and not maintained as levels decrease

describe the role of prolactin in the bitch

• prolactin acts as the main luteotrophic hormone after day 21, stimulated by an initial decline in progesterone

• it helps to support the CL and maintain progesterone levels but they gradually decline

what surgical procedure will result in pregnancy loss

• ovariectomy - as progesterone, which is only produced by the CL is required

describe how we can achieve termination of the luteal phase synthetically

• repeated administration of prolactin inhibitor but ONLY after 21 days

why will a prolactin inhibitor only be affective at terminating the luteal phase in the bitch after 21 days?

• prolactin must be the principle luteotrophic hormone

what does terminatino of the luteal phase lead to in the bitch?

• anoestrus

state 2 roles of elevated progesterone in the non-pregnant bitch

1. mammary tissue enlargement

2. potential for milk secretion

describe 2 roles of elevated prolactin in the non-pregnant bitch

• milk production

• behavioural changes typical of pregnancy

due to the prolonged period of hig progesterone in the bitch, what symptom is common in these animals?

• pseudopregnancy - considered a normal part of their cycle

describe the cyclicity of the queen

1. seasonal long day breeder

2. polyoestrus

3. induced ovulator

why does the time of puberty vary in queens?

• as cats are seasonal long-day breeders, onset of puberty is influenced by the season

in which months do we see repeated oestrus signs in the queen?

• march → october

what does an absence of ovulation ina queen cause?

• regression of follicles

what does a queen require for ovulation to take place

• stimulation aka mating - they’re induced ovulators

what is the average interval between oestrus in a queen

• 16-21 days

if a cat doesn’t ovulate, what part of her cycle does she therefore not experience?

• luteal phase

why is multiple matings needed for the queen to become pregnant?

• mating stimulates surge centre, but the stimulus must exceed the threshold for the LH surge to take place and therefore ovulation

when is the greatest response to mating in queens in her cycle?

• mid-oestrus - magnitude of LH surge changes on day of cycle

what is meant by a pesudopregnancy in a cat, is this normal?

• ovulation occurs but she doesn’t become pregnant

• causes a long luteal phase = 45 days

in which species is pseudopregnancy:

1. normal part of cyclicity

2. abnormal

1. bitch

2. queen

how long does ovulation + pregnancy take in a queen?

• roughly 68 days