PA Repro

Length of dairy cow oestrous cycle

18-22d

Length of beef cow oestrous cycle

22-24d

How many follicle waves usually occur in the dairy and beef cow oestrous cycle

Dairy = 2
Beef = 3

How quickly must cows get pregnant again to achieve yearly calving

3 mth PP

4 reasons for prolonged interval to resumption of the oestrous cycle in ruminants

Decreased BCS
Maternal bond
Metabolic state/negative energy balance
Disease

Best method for heat detection in cows

Behavioural observations 3-5x/day (very labour intensive)

When should a cow receive AI after heat detection

am/pm rule - if seen in heat in the morning, AI in the afternoon

if seen in heat in the afternoon, AI the following morning

When will an increase in milk/plasma progesterone occur due to pregnancy in cows

22-26d

When should the first transrectal U/S be performed for pregnancy diagnosis in cows

28d (>25d)

When can the amniotic vesicle be palpated in pregnant cows

42d

When can the placentomes be palpated in pregnant cows

2.5m

When can fremitus be felt in pregnant cows

>3.5m

Length of the oestrous cycle in the ewe

17d

How many follicle waves occur in the ewe oestrous cycle

2-4

When does ovulation occur in the ewe

End of oestrus

2 routes for multiple ovulations in the ewe

Co-dominant follicles
Ovulations from multiple follicle waves

What synchronises the oestrous cyclicity in ewes

Melatonin

NDO cows

Not detected in oestrous

Target for % dairy cows serviced by 80d PP

75%

Target for % dairy cows in calf by 100d PP

50%

'Days open'

time from parturition to conception (includes 1st heat expression, 1st ovulation and conception rates)

Factors affecting days open in dairy cows

Yield
Low BCS
Post-partum disease (milk fever, mastitis, dystocia, RFM, endometritis, lameness, C-section)

Why do high yield dairy cows have more days open

Selected for milk production rather than fertility

4 general causes of NDO cows

Anoestrus and anovulation PP with dominant follicle (DF) turnover
Low oestrus expression despite ovulation
Cystic ovarian disease (no oestrus, no DF turnover)
Prolonged PP luteal phase (no oestrus, persistent CL)

Risk factors for dairy cows entering anoestrus/anovulation PP

Low BCS (about 1/3 at BCS3 will also experience)
Loss of BCS - risk to fat cows esp.

Why do high yielding dairy cows show less oestrus behaviour

Increased metabolic rate = increased hepatic blood flow = increased metabolism of oestrogens/progerstrogens = decreased circulating oestradiol (decreased oestrus behaviour) and progesterone (decreased fertility)

Why can high yielding dairy cows be more prone to twins

Increased metabolic rate = increased metabolism of hormones = decreased circulating oestradiol = increased FSH = increased ovulation of co-dominant follicles = twins

Why does uterine infection PP cause a prolonged luteal phase and therefore increasing days open

Uterine infection = decreased uterine hormone production = CL not broken down = persistent CL

Above what size is a follicle deemed pathological

2cm

2 types of ovarian cysts

Follicular - thin-walled, high oestradiol secretion
Luteal - thick-walled, high progesterone secretion

Risk factors for cystic ovarian disease in cows

High yielders
Older animals
Higher BCS at calving
Uterine pathology PP
High phytoestrogen diet (e.g. red clover)

Diagnosis of cystic ovarian disease in cows

NDO cows with an ovarian cyst

Treatment for cystic ovarian disease in cows

Follicular cyst = GnRH to cause ovulation (+/- progesterone implant to cause follicular atresia)
Luteal cyst = PGF2a

Submission rate (SR) =

(No. served / no. eligible) x 100
(In 21d period)

Conception rate (CR) =

(No. pregnant / no. served) x 100
(In 21d period)

Pregnancy rate (PR) =

(No. pregnant / no. eligible) x 100
(In 21d period)

Submission rate target for cows (beef and dairy)

90%

Conception rate targets for cows (beef, seasonal and year-round dairy)

Beef = 60%
Seasonal dairy = 50%
Year-round dairy = 40%

Pregnancy rate targets for cows (beef, seasonal and year-round dairy)

Beef = 45%
Seasonal dairy = 40%
Year-round dairy = 25%

3 costs of decreased herd fertility in cows

Decreased production per cow
Decreased potential replacements ( = older/ill cows kept = less productive)
Slower genetic gains (= less future production potential)

Sensitivity of heat detection

% served that were on heat

Specificity of heat detection

% served that were not on heat

How long should the inter-service interval be in cows

21d (18-24)

Factors affecting herd fertility

Heat detection
Lameness
Transitional cow diseases
Nutrition
Infectious diseases
Semen management
Genetics
Mastitis

Why does lameness affect herd fertility

Increased lying times, decreased oestrus behaviour, decreased CR
Lameness = decreased CR and PR = decreased replacements = have to keep lame cows = increased prevalence of lameness in herd

Incidence of transitional cow disease =

No. disease / no. calvings

What records do you want to see for a herd fertility investigation

Calvings
AI/services
PD
Abortions
Excluded animals (do not breed and those leaving the herd)
Purchased animals
Also:
Diseases
Heat detection methods
Bull/AI technician

After what time are foetal membranes considered retained in cows

6-12h

Risk factors for RFM in cows

Premature birth/induced calving
Poor hygiene at birth
Hormones
Infectious placentitis
Overstretching of myometrium (e.g. twins, dystocia)
Hypocalcaemia
Various vitamin deficiencies

Signs of RFM in cows

Putrefaction/foetid smell
Pyrexia, inappetance
Tenesmus
Diarrhoea
Laminitis
Mastitis
Death

Treatment of RFM in cows

Not pyrexic = monitor temp.
Pyrexic = oral Abs, NSAIDs, +/- fluids

Prevention of RFM in cows

Transition period management
Breeding management (avoid dystocia)
Hygiene at calving

When does acute PP metritis occur in cows

1-21d PP

2 most common causative agents of acute PP metritis in cows

E. coli
T. pyogenes

Risk factors for acute PP metritis in cows

RFM
Poor calving hygiene
Immunosuppression
Vaginal tears (more common in heifers)

Signs of acute PP metritis in cows

Depression, inappetance, pyrexia
Vaginal discharge (watery, smelly, red/brown)
Distended uterus
Death

Treatment for acute PP metritis in cows

Oral ABs
NSAIDs
Fluids

Prevention of acute PP metritis in cows

Hygiene
RFM prevention
Heifer management (avoid dystocia)

How many days PP does chronic endometritis occur in cows

21-45d

3 main causative agents of chronic endometritis in cows

E. coli
T. pyogenes
F. necrophorum

Signs of chronic endometritis in cows

Systemically well
Purulent vaginal discharge
Uterus not fully involuted
May be asymptomatic

Diagnosis of chronic endometritis in cows

Vaginal discharge
Cervical exam
Palpation and U/S
Uterine lavage
Cytobrush cytology
Bacteriology swabs

Treatment of chronic endometritis in cows

Variable results
Intrauterine Abs
PGF2a if CL present

When does pyometra occur PP in cows

>30d

What type of pyometra is usually seen in cows

closed

Diagnosis of pyometra in cows

U/S - pus in uterus and CL present
Anoestrus cow

Treatment for pyometra in cows

PGF2a
Intrauterine Abs

3 main options for manipulating the bovine oestrous cycle

PGF2a injection to synchronise luteolysis
Progesterone implant to prevent oestrus for a set time
GnRH and PGF2a to synchronise ovulation (Ovsynch)

What is required for a PGF2a treatment to synchronise luteolysis

Functional CL

Can single PGF2a injection be used with fixed-time AI

no - ovulation time will be variable as cows will have had follicles in different stages

In a double PGF2a protocol for bovine synchronisation, how long is left between the PGF2a injections

11d

When should fixed-time AI be used after a double PGF2a protocol

60h and 84h (double AI_

Will cows have normal fertility after a PGF2a synchronisation protocol

yes

Which of the 3 generic approaches to bovine cycle manipulation produces the most reliable oestrus

Progesterone protocol

Progesterone protocol for bovine synchronisation

Progesterone implant (PRID/CIDR)
PGF2a given before device removed (at least 7d after starting protocol)
Ovulation/oestrus 2-3d later

When should fixed-time AI be used in a progesterone synchronisation protocol in the cow

Single AI = 56h
Double AI = 48 and 72h

Does it matter when in the cycle the progesterone synchronisation protocol in cows is started

No - the progesterone implant causes rapid atresia of any existing dominant follicles

DO cows have normal fertility after the use of a progesterone synchronisation protocol

yes

What is synchronised by OvSynch (GnRH and PGF2a protocol)

Ovulation (NOT oestrus)

OvSynch (/GnRH and PGF2a) protocol in cows

GnRH given - 7d later PGF2a given - 2d later GnRH given
Ovulation 24-30h later

When should fixed-time AI be used after an OvSynch protocol

16-24h

Is a functional CL required for a progesterone synchronisation protocol

no

Is pregnancy rate normal with OvSynch and fixed-time AI

No - decreased as not all cows ovulate from GnRH1 = can't ovulate at GnRH2

How can the pregnancy rate be improved with OvSynch and fixed-time AI

Use a progesterone device in the week between GnRH1 and GnRH2

Options for induction of 1st ovulation

Break maternal bond (beef sucklers) - remove calf
GnRH injection (or hCG) - will not show oestrus, can't AI
OvSynch - allows timed AI, but will have a lower conception rate unless pre-synch progesterone used, eCG can also be used when device removed to produce a very reliable oestrus 48h later

Problem of using eCG in cows

If high dose used, can cause multiple ovulations = twins

First 3 questions when investigating a sub/infertility issue in a herd

Beef vs dairy
Cows vs heifers
When do the fertility problems occur - SR vs CR vs management issue

How is ovulation checked in a cow

U/S for CL and milk/blood progesterone

Causes of cows with no ovulation and no oestrus

True anoestrus/anovulation
Recent ovulation, not yet picked up on U/S
Cystic ovarian disease
Congenital issue in heifers (e.g. freemartin)

Causes of cows with no oestrus but are ovulating

Heat detection issue (frequency, ability)
1st ovulation (PP or puberty) - will not show oestrus
High yielding dairy cows
Calf presence with suckler cows
Stress
Persistent CL

Causes of cows with irregular oestrus and ovulation

Oestrus detection issues (frequency, ability)
1st/2nd ovulation PP/puberty (1st cycle will be short)
PGF2a administration (accidental, issue with records)
Short luteal phase (v. rare)

Cause of cows with irregular oestrus and no ovulation

Cystic ovarian disease

3 categories of pregnancy/ conception failure in cows

Fertilisation failure
Failure of maternal recognition
Late embryonic losses

Diagnosis of fertilisation failure in cows

Normal/shortened inter-oestrus interval (12-24h)
Possible adhesions/genital abnormalities on rectal exam

Causes of fertilisation in cows

Bull infertility
AI timing/technique
Cervical/uterine abnormalities (congenital vs acquired)
Genetic abnormalities in the oocyte
Delayed ovulation in high yielding dairy cows

Diagnosis of failure of maternal recognition of pregnancy in cows

Normal/shortened inter-oestrus interval (12-24h)
+/- Discharge at next oestrus

Causes of failure of maternal recognition of pregnancy

Ovulation of persistent dominant follicle (old oocyte)
Genetic abnormalities
Impaired CL function
Infection (IBR, BVD, tritrichomonas fetus, campylobacter)
Endometritis (E. coli, T. pyogenes)
Nutrition
Heat stress

Causes of a group of cows to not become pregnant after multiple AIs

Problem with AI (timing, technique) or bull
PP diseases
Endometritis (inc. subclinical)
Infections

When do late embryonic deaths occur in cows

24d - 6w