Fertility of Natural Vs Synchronized Estrus

Synchronizing estrus is an effective way to maximize the use of time and labor required to detect standing estrus in cattle. However, estrous synchronization can also benefit overall herd management. Cows that are synchronized 1) exhibit standing estrus at a predicted time, 2) conceive earlier in the breeding season, 3) calve earlier in the calving season, and 4) wean calves that are older and heavier at weaning. In addition, some estrous synchronization protocols can induce a proportion of anestrous cows to begin estrous cycles. This will decrease the anestrous postpartum interval and allow for more chances for cows to conceive during a defined breeding season. The term “Estrous Synchronization” simply implies the estrous cycle is manipulated to cause a large group of cows to exhibit standing estrus around the same time. However, the question is often asked, “Do estrous synchronization protocols increase or decrease fertility?” To answer this question a measurement of fertility must be defined (see below) and then compared between non-synchronized and synchronized females.