Classification of anoestrus in cattle

Benefiting from the use of ultrasonography and growing knowledge of follicular dynamics in cattle Wiltbank et al. (2002) proposed the following classification of anovulatory status:

Anovulation with follicle growth up to the emergence stage

  • Cows exhibit very small follicles that are growing only to the emergence phase and do not proceed further.
  • Fairly common in cattle exposed to poor feeding conditions such as extensive pasture management in tropical zones.
  • The underlying factor is inadequate FSH stimulation

Anovulation with follicle growth up to deviation phase

  • Follicular growth takes place and proceeds through emergence and deviation but does not lead to ovulation.
  • A frequently reported form of anoestrus. Commonly occurs in the post partum period in lactating dairy and suckled beef cows.
  • The characteristic signs of this condition are small ovaries, with the absence of a corpus luteum or ovulatory size follicles. The ovaries however show continuing follicular growth in a dynamic wave pattern up to the deviation phase.
  • The underlying physiological problem is an inhibitory effect of oestradiol on GnRH/LH pulses that does not allow the final growth or oestradiol production by the post deviation dominant follicle.

Anovulation with Follicle Growth to Ovulatory or Larger Size of Follicle

See Cystic Ovarian Disease (COD).

milking parlour

Milking parlour

rectal examination

Uterine palpation via rectal examination