Conception and Embryonic Resorption

Question 1

Difference between conception failure and embryonic death

Answer 1

Conception failure- no conception occurs
Embryonic Death- Loss before organogenesis is complete

Question 2

3 possible reasons for conception failure

Answer 2

Mis-timing of mating
Ovulation failure (or delayed)
Male infertility

Question 3

4 possible reasons for embryonic death

Answer 3

1. (Most common) Aberrant embryonic development and failure to be recognised by mother i.e. never truly pregnant. Inadequate pregnancy recognition substance produced
2. Chromosomal abnormalities
3. Losses in oviduct
4. Implantation occurs but pregnancy lost

Question 4

3 main reasons for early pregnancy loss in cattle

Answer 4

Conception failure occur and associated with
- Metabolic or physical stress
- Ovarian pathologies i.e. ovarian cysts
Oestrus detection (or lack of it)
Mis-timing of AI

Question 5

How does nutrition affect early pregnancy loss in cattle

Answer 5

Negative energy balance leading to low IGF1 and growth factor support to ovary / uterus
High NEFA: toxicity to ooycte
High protein leading to elevated urea concentrations -> lower oocyte and embryo quality
Mineral and micronutrient deficiencies

Question 6

Other causes of early pregnancy failure in cattle

Answer 6

Impaired embryonic development
Heat stress particularly if above 25oC
Infectious causes
- Campylobacter fetus
- BVDV
- BHV1
Damage of the endometrium
- Subclinical endometritis?
- Delayed endometrial repair

Question 7

What is the mechanism of poor embryonic development and how to reduce risks of it

Answer 7

Failure to secrete maternal recognition signal, due to
- Lack of progesterone
- Attenuated uterine secretions of histotroph
No product licensed but could stimulate progesterone production (GnRH/hCG) or
Supplement with progesterone
– 10% improvement in pregnancy rates2
– Timing and identification of problem animals is critical

Question 8

What is the aim for sheep when thinking about embryonic death

Answer 8

Want to maximise the number of offspring per ewe (2 per ewe is the goal)
As they often have multiple offspring embryo loss before implantation is unlikely to affect pregnancy- will still be pregnant with a single lamb

Question 9

3 example of infectious diseases which lead to high rate to oestrus return or high empty rate at PD

Answer 9

toxoplasmosis, Schmallenberg virus, Border disease

Question 10

How does nutrition in sheep affect embryonic death

Answer 10

Flushing to optimise number of ovulations
Grazing of red clover around mating: high phyto-oestrogen content can have negative effect

Question 11

How are pigs managed in relation to fetility and pregnancy loss
how soon after weaning do you aim to re-establish pregnancy
seasonal effects? reasons for ovulation failure?

Answer 11

Aim: re-establish pregnancy within one week after weaning
Seasonal effects: decreased fertility in summer and autumn1
Ovulation failure:
- Cystic ovarian disease (up to 10%); particularly after early weaning, stress and under-nutrition2
- Response to treatment is generally poor, culling is likely.
Peak fertility observed in pigs with 3-5 days weaning to oestrus interval

Question 12

3 factors which may affect failure to establish pregnancy in pigs

Answer 12

1. Genetics: Ovulation rates have doubled but embryonic survival rate declined over past 60 years. Assumed due to limited uterine capacity
2. Infectious causes:
   - Porcine parovirus (PPV): likely to cause embryonic death, resorption and repeat breeding. In fetal period, leads to mummification
3. Nutrition: feed restriction will lead to subfertility

Question 13

5 things that can lead to early pregnancy failure in the mare

Answer 13

1. Age of the horse: younger or older have lower pregnancy rates.
   
   • Potentially due to immaturity, inadequate nutrition or physical stress (young)
   • Might be acquired due to structural defects (older)

2.Haemorrhagic anovulatory follicles (HAFs)1

3. Uterine tube or uterine pathology due to inflammatory conditions or lack of histotroph
   
   • Endometritis due to delay in uterine clearance of bacteria post-foaling2
   • Specific infectious diseases including contagious equine metritis
4. Foal heat – breeding as early as 7-10 days post-partum:
   
   • Unclear if fertilisation failure or embryonic death but pregnancy rates are lower
5. Maternal stress due to: severe pain, under-nutrition or transport. Regular exercise in early pregnancy is still important

Question 14

Effect of progesterone on pregnancy failure in the mare

Answer 14

No evidence it improves pregnancy rates

Question 15

what is flushing

Answer 15

the practice of feeding a diet high in protein and energy in the last few weeks before tupping, can result in higher scanning rates (sheep)