What are some of the risk factors for postpartum cows to be anovular (non-cycling) for a prolonged length of time? Researchers at the University of Guelph set out to find some answers using data from 2,178 Holstein cows in six commercial herds. The results were published in the April issue of the Journal of Dairy Science.

The researchers tracked: 

  • Periparturient disease incidence.
  •  Calving score. 
  • Body condition.
Whether a cow ovulated early or had prolonged anovulation was associated with:
  • Negative energy balance. 
  • Uterine inflammation during the peripartum period. 
  • Milk production level. 
  • Parity. 
  • Season.
Cows that ovulated by 21 days in milk were associated with a shorter time to pregnancy. Conversely, and not surprisingly, prolonged anovulation was detrimental to subsequent reproductive performance and increased likelihood of culling.

The researchers cautioned that the effects of prolonged anovulation on reproduction were worse in cows of third parity or greater, recommending that producers apply targeted mitigation strategies to those groups of cows.