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=== Oestrous Cycle ===
 
=== Oestrous Cycle ===
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* Polyoestrous
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* The first ovulation in heifers is usually without behavioural oestrus.  This is termed 'silent heat'.
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* Cyclical activity persists except during pregnancy, for 3-6 weeks post-calving and during high milk yield.
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* In heifers, the average length of the oestrous cycle is 20 days (18-22).
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* In cows, the average length of the oestrous cycle is 21 days (18-24).
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* The average duration of oestrus is ~ 15 hours (2-30 hours).
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* The body temperature of dairy cows dalls ~0.5◦C the day before oestrus.  It then increases in oestrus before falling by ~0.3◦C at ovulation.
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* Vaginal pH also fluctuates throughout the oestrous cycle, but is lowest (7.32) on the day of oestrus.
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* Ovulation is spontaneous, occuring ~12 hours after the end of oestrus.
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* Within 2 days of service, there is yellow-white vulval discharge of mucus.  This contains neutrophil leucocytes from the uterus.
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* At ~48 hours post-oestrus, irrespective of service, there is a bright red sanguineous discharge from the uterine caruncles.
    
= Links =
 
= Links =
    
[[Oestrous_Cycle_-Pharmacological_Manipulation_of_Oestrous_Cycles_-_Anatomy_%26_Physiology|Pharmacological Manipulation of Oestrous Cycles]]
 
[[Oestrous_Cycle_-Pharmacological_Manipulation_of_Oestrous_Cycles_-_Anatomy_%26_Physiology|Pharmacological Manipulation of Oestrous Cycles]]
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