Reproductive failure 2 - Non-infectious causes Flashcards
Explain the difference in the oestrus cycles (cycle and oestrus length as well as time of ovulation) of cattle, sheep, pig and horse.
- Cattle: 21d cycle, 18h oestrus and ovulation 11h after oestrus ends
- Sheep: 17d cycle, 29h oestrus and ovulation near the end of oestrus
- Pig: 21d cycle, 48-72h oestrus and ovulation 35-45h after the start of oestrus
- Horse: 21d cycle, oestrus length is 4-8d and ovulation is 3-6d after oestrus starts.
List polyoestrus species
Cor, pigs, cats and rodents
List seasonal polyoestrus species
Long day breeder: mare
short day breeder: sheep and goat
List monoestrus species
Dog, wolf, fox and bear
What are the 7 non infectious causes of reproductive failure?
- Failure to mate
- failure to ovulate
- failure to fertilise
- embryonic death
- failure to implant
- foetal mortality
- perinatal mortality
What may lead to a failure to mate? Explain each factor.
- Season: photoperiod or heat stress
- Male: Age (need to be sexually mature), libido or injury
- Female: Age, silent oestrus, aggression or protection of offspring
- Competition in the flock/herd mating: male preference or insufficient male to female ratio
- Congenital abnormalities: include things such as cryptorchidism, gonadal hyperplasia, penile deviation, freemartinism or hermaphroditism (intersex)
What may lead to a failure to ovulate? Explain each factor.
- Oestrus without ovlation: occurs at the onset of puberty, during transition to breeding season, imbalance of FSH and LH
- Cystic follicles: common in dairy cattle and swine, associated with high milk production, hereditary predisposition, LH release disrupted
What may lead to a failure to fertilise? Explain each factor.
- Infertile or sub-fertile male: overuse, injury, season, heat stress
- Impaired sperm transport: can be due to female factors or an anatomical abnormality. Phytoestrogens (eg clover disease) may play a role
- Abnormal oocytes or sperm: age plays a role in both genders
- Inappropriate timing of insemination
- Nutritional stress: delays onset of puberty, reduces oestrus cyclicity and ovulation rate, detrimental to foetal development (reduces offspring birthweight and lifetime performance), decreased lactation
- Environmental stress: extreme heat or cold or drought
- Handling stress
What may lead to a embryonic failure/death? Explain each factor.
- Embryonic death: in all mammalian spp. 30-40% of embryos are lost, majority occur prior to maternal recognition of pregnancy so cant be distinguished from fertilisation failure. Those that occur after the maternal recognition of pregnancy have a late or delayed return to oestrus whereas unrecognised losses have a normal return to oestrus.
- Non-viable embryo: lethal genetic defect, delayed timing of fertilisation or insemination (oocyte ages and loses viability), maternal recognition of pregnancy
- Poor oviductal/uterine environment: CL failure, hormone imbalance, abnormal embryo trasnport, inadequate support of embryo development, failure to implant, failure to maintain pregnancy.
What may lead to failure to implant?
Poor oviductal or uterine environement due to:
- CL failure (hormonal imbalance)
- abnormal embryo transport
- inadequate support of embryo develepment
What may lead to a foetal mortality? Explain each factor.
- Non-viable foetus or uterine deficiency –> foetus absorbed early pregnancy
- uterine crowding
- undernutrition: high energy demand in late pregnancy, pregnancy toxaemia (where the breakdown of fats become toxic)
What may lead to perinatal mortality? Explain each factor.
- Dystocia
o Multiple pregnancy
o Abnormal foetal position
o Foeto-pelvic disproportion (oversized foetus)
o Primiparous dam - Hydrops: Fluid build-up in body of foetus
- Weak neonate
o Low birth weight
o Respiratory distress syndrome
o Mismothering/maternal bonding: Breed, age of mother - Predation
- Temperature stress (exposure)
- Mastitis starvation
- Accident
What are the methods of pregnancy and does this differ among species?
- Detection of a normal return to oetrus
- Ultrasonography
- transrectal palpation in cows and mares
- biochemical testing
What are some issues associated with biochemical testing for pregnancy diagnosis?
- Cost
- inconvenience of blood collection
- variability between animals
- false positives or negatives
- stringent quality control needed
- turnaround time from blood collection to return of result
What may be one reason a maiden ewe may fail to mate and/or raise a lamb?
- They have less overt oetrous behaviour so may not be picked up by the rams
- They have poorer maternal ability
- shorter oestrus
