Cattle Fertility Flashcards
Define:
a) a sub-fertile cow
b) a sterile cow
a) cow that fails to achieve a fertility target
b) cow that is incapable of becoming pregnant
How often will a heifer come into oestrus if she is not pregnant?
Every 18-24 days.
What are the different reasons why oestrus may not be seen?
- Congenital abnormalities e.g. ovarian hypo/aplasia. Most common is freemartinism
- True Acyclical or anoestrus cow
- Persistant CL +/- pyometra
- Ovarian cysts
- Limited behavioral signs with normal oestrus (silent heat)
- Lack of detection
How can freemartins be diagnosed?
Use a probe to test depth of vagina in comparison to heifers of a similar age. Confirm Dx by sending a blood sample off for karyotyping
What is/are the cause of true acyclicity?
- High energy requirement during the lactating period which is not met. This can also be caused by low BCS.
- Stress e.g. lameness/disease
How can anoestrus be dx?
Milk progesterone at 10 day intervals
small follicles no CL
Involuted tract on palpation, also small, flat ovaries
Explain the principles of treatment of the anoestrus cow.
There is low level gonadotrophin production therefore suppress this residual activity with progesterone treatment. This can be combined with GnRH (which can also be given alone) or eCG low dose. n.b. that response to treatment often better if nutrition improved
What are the different types of ovarian cyst?
Follicular (thin walled) - Oestradiol secreting - nymphomania
Luteal cyst - thick walled P secreting (like a persistant CL)
Inactive cyst (thin) - no functional differentiation
What are ovarian follicular cysts and why are they accompanied by a cessation in cyclicity?
Un ovulated graffian follicle with granulosa cell degeneration. There is no ovulation of the follicle due to the lack in LH surge which is preceded by increased oestragen production by the mature follicle.
Why is there a failure of the pre-ovulatory LH surge?
After calving there is a recovery period where the hypothalamus is less sensitive to oestragen positive feedback. This may be due to the elevated progesterone levels during pregnancy.
Ovarian causes - reduced LH receptors. Or low insulin/IGF-1 levels due to NEB therefore increased NEFAs impair follicular cell proliferation.
What is the treatment for:
a) Luteal cyst
b) follicular cyst
a) PGF2a for luteolysis
b) GnRH/hCG to leutenise then PGF2a or progesterone treatment
How does a persistent CL occur?
Pathological changes due to pyometra result in failure of luteolysin action. This self perpetuates the disease
How often should cows be observed for oestrus?
20-30 mins 3x per day especially at quiet time around 9-10pm.
What can be done to aid detection of heat/improve the problem?
Use heat detection aids
Synchronize oestrus
Run a bull within the herd for natural service
How can oestrus be synchronised?
PGF inj. x2, 11 days apart with:
- AI at 72-84hrs after 2nd inj.
- double AI at 72 and 90/96hr
PRID/CIDR 7-9days + PGF inj. 24hrs prior to removal
- Double AI 48&72 hrs post inj.
- AI @ 56hr
Outline the basic ovysynch structure.
- GnRH to synchronise new wave emergence
- PGF @ 7d to luteolyse
- GnRH @ 9d to ovulate
- AI @ 10d
What are the reasons for AI failure?
- Failure to fertilise
- Embryos die < 13 days
- Embryos die 13-42 days
- Embryos die after 42 days (abortion, maceration, mummification)
What are regular and irregular returns to oestrus?
returns to oestrus are when a cow returns to oestrus following AI
Regular - 18-24 days post AI, due to fertilisation failure/early embryonic death
Irregular - >24 days, later embryonic death/early foetal death
What are the causes of fertilisation failure other than due to poor semen?
Anovulation Delayed ovulation Incorrect AI timing Serving too early postpartum Hormonal problems Structural problems of genital tract so sperm and oocyte cannot meet Infection Nutritional imbalances Stress
When should AI be timed?
12hrs after detection of heat
What can cause embryonic death?
Luteal deficiency (lack of P) Uterine infection with specific pathogens Oppertunist pathogens/endometritis Nutritional imbalances Genetics factors Stress
What are the specific embryopathic micro-organisms?
Campylobacter fetus Tritrichomonas fetus Mycoplasma, ureaplasma, acholeplasma BVDV Infectious bovine rhinotracheitis (IBR), BTV Chlamydophila psittaci
What is a repeat breeder?
One that has returned to oestrus on 3-4 consecutive occasions.
What can be done to treat a repeat breeder when the cause is non-infectious?
Use a better semen/sire
Inseminate once then 24hrs later
hCG or GnRH at time of insemination
GnRH/Progesteron 11-12 days after insemination
Treat infection/endometritis
What is the best way to dx endometritis?
Vaginal exam
Sensitivity score
What are the frequent causes of endometritis?
Trueperella pyogenes Prevotella spp. E. coli Fusobacterium necrophorum F. nucleatum
How is endometritis treated?
Use PGF2a if there is a CL present: oestrus is immunoprotective whereas progesterone is immunosuppressive.
No CL: intrauterine cephalosporin
What is the definition of abortion?
Expulsion of calf <24hrs
What are the non-infectious causes of abortion/stillbirth?
Genetic/developmental abnormalities Hormonal imbalances Toxic substances Heat stress Iatrogenic Dystocia
