A:   Beef cows usually have a 21 day estrous cycle with day 0 being the first day of the cycle and day 21 being the day of ovualtion. There are a number of items that can disrupt the 21 day cycle. Cows after calving will typically not cycle for 50 to 55 days after calving. During that time they are repairing their reproductive tract for another pregnancy. Also, they are lactating during this time period and the reproductive axis needs to over-come this before they will resume normal estrous cycles. Heavy lactation will impact when cycles begin after calving as will difficult birthing or calving. Nutrition will also impact estrous cycles. Thin cows may be anestrous and until they gain body condition, they will not cycle. Sometimes beef cows may develop follicualr cysts. It doesn't happen that often and happens more in dairy cows. There are two ways that they are treated, one being administered GnRH to promote ovulation. Sometimes cows need to be treated more than once. The other way is to manually pinch the cyst via rectal palpation to cause the cyst to rupture.