Cattle Fertility

Question 1

Define:

a) a sub-fertile cow

b) a sterile cow

Answer 1

a) cow that fails to achieve a fertility target

b) cow that is incapable of becoming pregnant

Question 2

How often will a heifer come into oestrus if she is not pregnant?

Answer 2

Every 18-24 days.

Question 3

What are the different reasons why oestrus may not be seen?

Answer 3

• 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

Question 4

How can freemartins be diagnosed?

Answer 4

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

Question 5

What is/are the cause of true acyclicity?

Answer 5

1. High energy requirement during the lactating period which is not met. This can also be caused by low BCS.
2. Stress e.g. lameness/disease

Question 6

How can anoestrus be dx?

Answer 6

Milk progesterone at 10 day intervals
small follicles no CL
Involuted tract on palpation, also small, flat ovaries

Question 7

Explain the principles of treatment of the anoestrus cow.

Answer 7

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

Question 8

What are the different types of ovarian cyst?

Answer 8

Follicular (thin walled) - Oestradiol secreting - nymphomania

Luteal cyst - thick walled P secreting (like a persistant CL)

Inactive cyst (thin) - no functional differentiation

Question 9

What are ovarian follicular cysts and why are they accompanied by a cessation in cyclicity?

Answer 9

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.

Question 10

Why is there a failure of the pre-ovulatory LH surge?

Answer 10

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.

Question 11

What is the treatment for:

a) Luteal cyst
b) follicular cyst

Answer 11

a) PGF2a for luteolysis

b) GnRH/hCG to leutenise then PGF2a or progesterone treatment

Question 12

How does a persistent CL occur?

Answer 12

Pathological changes due to pyometra result in failure of luteolysin action. This self perpetuates the disease

Question 13

How often should cows be observed for oestrus?

Answer 13

20-30 mins 3x per day especially at quiet time around 9-10pm.

Question 14

What can be done to aid detection of heat/improve the problem?

Answer 14

Use heat detection aids
Synchronize oestrus
Run a bull within the herd for natural service

Question 15

How can oestrus be synchronised?

Answer 15

PGF inj. x2, 11 days apart with:

1. AI at 72-84hrs after 2nd inj.
2. double AI at 72 and 90/96hr

PRID/CIDR 7-9days + PGF inj. 24hrs prior to removal

1. Double AI 48&72 hrs post inj.
2. AI @ 56hr

Question 16

Outline the basic ovysynch structure.

Answer 16

1. GnRH to synchronise new wave emergence
2. PGF @ 7d to luteolyse
3. GnRH @ 9d to ovulate
4. AI @ 10d

Question 17

What are the reasons for AI failure?

Answer 17

• Failure to fertilise
• Embryos die < 13 days
• Embryos die 13-42 days
• Embryos die after 42 days (abortion, maceration, mummification)

Question 18

What are regular and irregular returns to oestrus?

Answer 18

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

Question 19

What are the causes of fertilisation failure other than due to poor semen?

Answer 19

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

Question 20

When should AI be timed?

Answer 20

12hrs after detection of heat

Question 21

What can cause embryonic death?

Answer 21

Luteal deficiency (lack of P)
Uterine infection with specific pathogens
Oppertunist pathogens/endometritis
Nutritional imbalances
Genetics factors
Stress

Question 22

What are the specific embryopathic micro-organisms?

Answer 22

Campylobacter fetus
Tritrichomonas fetus
Mycoplasma, ureaplasma, acholeplasma
BVDV
Infectious bovine rhinotracheitis (IBR), BTV
Chlamydophila psittaci

Question 23

What is a repeat breeder?

Answer 23

One that has returned to oestrus on 3-4 consecutive occasions.

Question 24

What can be done to treat a repeat breeder when the cause is non-infectious?

Answer 24

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

Question 25

What is the best way to dx endometritis?

Answer 25

Vaginal exam

Sensitivity score

Question 26

What are the frequent causes of endometritis?

Answer 26

Trueperella pyogenes
Prevotella spp.
E. coli
Fusobacterium necrophorum
F. nucleatum

Question 27

How is endometritis treated?

Answer 27

Use PGF2a if there is a CL present: oestrus is immunoprotective whereas progesterone is immunosuppressive.

No CL: intrauterine cephalosporin

Question 28

What is the definition of abortion?

Answer 28

Expulsion of calf <24hrs

Question 29

What are the non-infectious causes of abortion/stillbirth?

Answer 29

Genetic/developmental abnormalities
Hormonal imbalances
Toxic substances
Heat stress
Iatrogenic
Dystocia