Infertility in farmed species Flashcards
What presentation is associated with infertility?
- animals that are not or do not appear to be cycling at all
- animals are cycling but do not conceive
- animals that conceive but do not maintain pregnancy
What are possible causes for cows to not be cycling?
- Failure to observe oestrus (*this is NOT ‘true’ anoestrus)
◦ Failure to correctly recognise or to observe oestrus (covered later) - Metabolic/nutritional
◦ Negative energy balance, vitamin and trace element deficiencies - Uterine infection
◦ Pyometra/endometritis - Pregnancy
◦ Surprisingly common in practice - always check before giving PGF!!! - Cystic ovarian disease
◦ ~70% show anoestrus - Suckling calf at foot
◦ Most common cause of anoestrus in beef cows
What are possible causes for cycling cows that don’t conceive?
- Improper/incorrect insemination
◦ Timing, oestrus detection, technique, semen storage - Infectious causes
◦ Uterine infection prior to insemination
◦ Infection at/soon after breeding à early embryonic death or failure of conceptus - Toxins
◦ Mycotoxins, endotoxins (e.g. e-coli mastitis) - Metabolic/nutritional causes
◦ Negative energy balance, mineral deficiencies - Iatrogenic causes
◦ Improper use of hormonal drugs - Sire choice
◦ Semen abnormalities (see male fertility lectures)
What are possible viral causes of infertility?
BVD - Cattle
* Early embryonic death (EED)
* Ovarian damage
* Presentation:
◦ Long returns to service (25-35d)
◦ Reduced conception rates
Border disease - Sheep and goats
* Poor fertility
* presentation: Increased barren rate
IBR (BoHV-1) - Cattle
* Temporary ovarian necrosis
* Follicular degeneration
* Presentation: Reduced conception rates due to reduce ovulation capacity and reduce oocyte viability
What are bacterial and protozoal causes of infertility?
Leptospira - Cattle (zoonotic)
NB. Sheep can become infected and act as carriers but rarely show disease
* Poor fertility and EED –> possibly due to endometrial inflammation (exact mechanism unknown)
* presentation - Reduced conception rates and long returns to service (25-35d)
Brucella - All ruminants (reportable)
* Poor fertility
* Epididymitis and orchitis
* Presentation:
◦ Reduced conception rates (cattle) increased barren rate (sheep)
◦ Often initially presents as poor conception/barren rates in females
Campylobacter - Cattle and sheep
* Endometritis (cattle)
* Failure to conceive
* Early embryonic death (cattle)
* Abortion (sheep and cattle)
* Presentation:
◦ Irregular oestrus cycles, repeat breeding à long calving intervals
◦ Returns to oestrus
◦ Long returns to service (25-35d)
◦ Visible abortion
Tritrichomonas - Cattle
* Early embryonic death
* Pyometra and endometritis
* Presentation:
◦ Long returns to service (25-35d)
◦ Identified on clinical exam
What are infertility causes specific to heifers?
- May not have reached puberty
◦ Related to diet - May have reproductive tract abnormalities –> diagnose using scanner or clinical exam
◦ Freemartinism
◦ Mucometra (rare)
What kind of cysts can be produced in cystic ovarian disease? How are they differentiated? What is the aetiology of COD?
Cysts may be follicular or luteal
- Diagnosis is primarily using US scanning
◦ Progesterone testing can be helpful but rarely done
◦ Manual palpation has low accuracy
Aetiology
* Dominant follicle does not ovulate and continues to grow
◦ Failure of hypothalamus to secrete enough GnRH to stimulate LH surge (to cause ovulation)
‣ Related to failure of oestrogen feedback on hypothalamus
‣ Also related to metabolic effects on GnRH production
- No ovulation means no CL development and no luteal phase
- No CL = no progesterone
- Lack of progesterone contributes to behavioural changes seen and inhibits upregulation of LH receptors –> reproductive cycle stops
What are risk factors for COD? What are the presenting signs?
COD risk factors:
* Negative energy balance
* Age
◦ Older cows at higher risk
* High productivity
* Postpartum disease
* Difficult calving
* Stress
* Genetics
COD presenting signs
* Most (> 70%) affected cows will present due to anoestrus
◦ Not seen bulling (NSB)/no detected oestrus (NDO)/oestrus not seen (ONS)
- Remaining 30% will show excessive oestrus activity or occasionally irregular oestrus activity
◦ More common if cysts develop later in lactation - Most often seen in high yielding dairy cows
- Most often seen in early to peak lactation
What are the visual differences between follicular and luteal cysts?
Follicular cysts
* Thin wall (< 3mm)
◦ May be so thin it cannot be visualised
* Anechoic centre
* Low progesterone concentration (blood/milk test)
Luteal cyst
* Thick wall (>3mm – usually is 4-5mm)
◦ Wall is of the same echogenicity as a CL because it is comprised of luteal tissue
* Anechoic centre but may contain some hyperechoic strands
* High progesterone concentration (blood/milk test)
How are cysts treated?
Many cysts will self-resolve in time
- Luteal cysts = prostaglandin (synch protocols that include PGF can also be used)
◦ Aim to induce luteolysis - Follicular cysts = many options (see later), NOT prostaglandin
◦ Aim to address lack of LH stimulation that is inhibiting ovulation
Manual rupture not recommended
* Adhesions
* Haemorrhage
What are available treatments for suboptimal fertility in female cattle? How do these work?
Gonadotrophin releasing hormones (GnRH)
* Stimulates release of FSH and LH
Variety of indications
◦ Treat follicular cysts
◦ Treat anoestrus cows
◦ Stimulate ovulation in repeat breeder cows
◦ Key component of synch protocols
- Available as either a synthetic analogue (buserelin) or a synthetic form of bovine GnRH (gonadarelin)
- Practically there is little difference, and the product used is usually what you have in the practice
Prostaglandins (PGF2a)
* Cause luteolysis of CL –> fall in progesterone resulting in FSH and LH release
* Only work if CL or luteal cyst is present
* CL only sensitive to PGF2α between days 5 – 15 of cycle
◦ >17mm diameter on US scan
Variety of indications
* Treat luteal cysts
* Synch protocols
* Induce abortion or parturition
* Treat pyometra
* Control of breeding and oestrus timing
Available as naturally occurring PGF2α (dinoprost) or as a synthetic analogue (cloprostenol)
Progesterone
* Acts as an exogenous CL –> release progesterone and suppress GnRH release
* Dominant follicle develops –> does not ovulate
* Removal of device –> LH surge –> ovulation
Available as intravaginal devices (PRID and CIDR)
Variety of licensed uses
* Treat cysts
* Synch and embryo transfer protocols
* Improvements in oocyte quality
* Reduce time to service (seasonal herds)
* Repeat breeders
Products available –> impregnated silicone devices
* CIDR (controlled internal drug release)
* PRID (progesterone releasing intravaginal device)
What are common factors affecting exhibition of oestrus behaviour?
- Environmental
◦ Housed/outdoors
◦ Flooring - slipping
◦ Other activities - Health
◦ Factors affecting ability to stand
‣ e.g. Lameness
◦ Factors influencing oestrus cycle
‣ e.g. Cystic ovarian disease
◦ Pregnancy - Breed
◦ Bos indicus breeds shorter heat periods than Bos taurus breeds (6-12hrs vs. 8-14hrs) - Production
◦ High yielding cattle have shorter heat periods - Missing cows that are showing oestrus behaviours
◦ Cows not showing oestrus (see previous slide)
◦ Inadequate training of staff - Correct oestrus detection but too few cows identified
◦ Time constraints
◦ Poor lighting - Incorrect identification of oestrus (i.e. classifying cows that are not in oestrus as being in oestrus)
◦ Inadequate staff training
What are methods to improve oestrus detection in cows?
- Improved staffing
◦ More time
◦ More training - Improved environment
◦ Improvements for cows to show oestrus
◦ Improvements for people to see oestrus - Oestrus detection aids
- Cow worn devices measuring activity (Pedometers & Accelerometers)
- Visual indicators of oestrus behaviour
- Typically indicate has stood to mount for cows
- Tail chalk –> if rubbed off indicates has been mounted
- Heat patch (Kamar) –> stick onto tail head and change to red if mounted for > 3s
- Synchronisation protocols
◦ Removes need to observe oestrus if fixed time AI used
◦ Provides narrower time frame over which oestrus needs observing if service to observed oestrus used
