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Why does fertilisation failure occur?
Timing of insemination has an important influence on the success rate.
Influence of the timing of insemination on success rate.
Influence of the timing of insemination on success rate.
Fertilisation failure occurs due to many reasons, these are some of the most important:
Only the observation of a large follicleSmall secretory or excretory cavity. Ovarian follicles grow until ovulation or female gamete emission. 24 hours after the end of heatAlso “oestrus”. Physiological and behavioural phenomena that precedes and accompanies ovulation in female mammals. enables late ovulationExpulsion of an ovum from the ovary in female animals. to be confirmed. Recent studies have confirmed that late ovulationExpulsion of an ovum from the ovary in female animals. may happen in up to 25% of high producing cows.
Only the biggest lesions of the oviductDuct through which female gametes are expelled from the ovary in animals. can be detected by rectal examination or ecography.
Cows under heatAlso “oestrus”. Physiological and behavioural phenomena that precedes and accompanies ovulation in female mammals. stress tend to have much poorer fertilization rates as compared to cows kept under temperature-comfort zones.
The success of AI depends on the % of animals inseminated at the right time (follicular phase).
A follicular ovarian cyst can cause nymphomania, in which the cow is frequently on heatAlso “oestrus”. Physiological and behavioural phenomena that precedes and accompanies ovulation in female mammals. and for longer periods than usual.
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Diagnostic aid!
When heatAlso “oestrus”. Physiological and behavioural phenomena that precedes and accompanies ovulation in female mammals. is regular:
When heatAlso “oestrus”. Physiological and behavioural phenomena that precedes and accompanies ovulation in female mammals. is irregular: |
Detection of early embryo mortality
There is no means for detecting early embryo mortality. Under research environment, early embryo mortality has been confirmed as the main source of pregnancy losses since fertilization rates tend to be above 85% for both natural breeding or artificial insemination.
Detection of late embryo mortality
Return to heatAlso “oestrus”. Physiological and behavioural phenomena that precedes and accompanies ovulation in female mammals. occurs between 18 and 25 days after insemination. In order to detect late embryo mortality, two pregnancy diagnoses are necessary: the first one been positive, then the next resulting negative. Some techniques for pregnancy diagnosis are palpation, ultrasound, and more recently PAG or PSPB blood essay.
