Conception and embryonic resorption Flashcards
What are the causes of conception failure?
Mis-timing of mating
Ovulation failure (or delayed)
Male infertility
What are the causes of embryonic death (loss before organogenesis)
Chromosomal abnormalities
Losses in oviduct
Aberrant embryonic development and failure to be recognised by mother i.e. never truly pregnant
Implantation occurs but pregnancy lost
Describe the features of early pregnancy loss in cattle
Very significant cause of subfertility
Pregnancy losses up to 40%
More common in dairy cows
Associated with high yield/NEB
High economic cost
Describe the features of early pregnancy loss in pigs
Significant problem
Associated with ovarian pathologies after weaning
Reduced litter size due to limited uterine capacity
Describe the features of early pregnancy loss in horses
Significant, but fertilisation rates are high
Pregnancy loss up to 24%; most loss occur before day 12
Loss do occur after this; associated with lack of embryonic mobility
Describe the features of early pregnancy loss in sheep
Uncommon, sheep have very good fertility
Management issues
Reduced twinning rates
Describe the features of early pregnancy loss in dogs
Uncommon
More likely mis-timing of mating
Non-pregnant dogs will be pseudopregnant
Describe the features of early pregnancy loss in cats
Uncommon
More likely conception failure due to inappropriate mating
What are the common causes of conception failure in cattle?
Associated with:
- Metabolic or physical stress
- Ovarian pathologies i.e. ovarian cysts
Oestrus detection (or lack of it)
Mis-timing of AI
Describe the factors affecting early pregnancy loss in cattle
Nutrition:
- NEB => low IGF1 and growth factor support to ovary/uterus
- high plasma free fatty acids or urea levels can be toxic to oocyte/embryo
- specific mineral and micronutrient deficiencies
Impaired embryonic development
Heat stress
Infectious causes e.g., campylobacter, BVDV, BHV1
Damage to endometrium:
- subclinical endometritis
- delayed uterine involution
How does heat stress contribute to embryo loss in cows?
Heat Stress →
- Direct effects on reproduction
- Reduced feed intake → Negative energy balance
- Hormonal disruption: ↓ GnRH & LH → ↓ Estrogen → Poor estrus expression
- Impaired follicle development → Poor oocyte quality
- Impaired CL activity → Compromised uterine environment
- Result: Embryo loss
Describe how poor embryonic development occurs
Failure to secrete maternal recognition signal, due to lack of progesterone resulting in attenuated uterine secretions of histotroph
What are the possible treatment options for poor embryonic development
No product licensed but could stimulate progesterone production with GnRH
Supplement with progesterone
Describe the factors affecting embryonic death in ewes
Multiple conception
Infectious diseases e.g., toxoplasmosis, Schmallenberg virus, Border disease
Nutrition:
- flushing to optimise number of ovulations
- grazing of red clover around mating
Management:
- early in breeding season
- ram:ewe ration
Describe the factors causing failure to establish pregnancy in pigs
Seasonal:
- decreased fertility in summer and autumn
Ovulation failure:
- cystic ovarian disease (particularly after weaning, stress and under-nutrition)
Genetics
Infectious causes e.g., porcine parvovirus (PPV)
Feed restriction
Describe the factors influencing early pregnancy failure in the mare
Age:
- young (immaturity, inadequate nutrition, physical stress)
- old (structural defects)
Haemorrhagic anovulatory follicles (HAFs)
Uterine tube or uterine pathology due to inflammatory conditions or lack of histotroph:
- endometritis due to delay in uterine clearance of bacteria post-foaling
- contagious equine metritis
Foal heat:
- breeding feasible as early as 7-10 day post-partum => lower pregnancy rates
Maternal stress:
- pain, under-nutrition, transport
- exercise important
What is the difference between conception failure and embryonic death?
Conception failure – Fertilisation doesn’t occur, or embryo fails to implant
Embryonic death – Fertilisation occurs, but embryo dies before maternal recognition of pregnancy
