The breeding season is really where it all begins, and utilizing estrous synchronization is an opportunity to get more females bred earlier in the season.
Typically, when producers hear the phrase “estrous synchronization,” they automatically think artificial insemination (A.I.); however, utilizing synchronization protocols have also been proven to be very effective in natural-service settings as well to still capture the benefits of estrous synchronization with A.I.
Natural-service synchronization protocols differ in that fewer injections are administered for estrus to not be grouped so tightly that bulls cannot cover all the cows. Fewer injections also mean fewer trips through the chute compared to A.I.-based synchronization protocols.
The most notable advantage is that with synchronization, an extra opportunity to be bred is placed at the beginning of the breeding season. This gives a majority of the herd an opportunity to be serviced twice in the first 30 days, allowing more females to become pregnant in a fixed-duration breeding season.
Monitoring bull power is necessary. A good thumb rule for determining appropriate bull-to-cow ratio is that bull age in months at the start of the breeding season is a good indication of how many females he can service. For example, a 26-month-old bull turned out with cows in May is expected to be able to service 26 cows during the 2020 summer breeding season. Due to a greater number of females in heat during a narrow time frame, it’s recommended that mature bulls, who have passed an annual breeding soundness exam (BSE), are utilized in natural-service protocols.
Ensuring cows are in adequate body condition and at least 45 to 60 days postpartum at a minimum are necessary to implement a successful synchronization protocol. For more information, including approved protocols and Excel-based tools for planning estrous synchronization, visit the Applied Reproductive Strategies in Beef Cattle (ARSBC) website by the Beef Reproduction Task Force. 
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Erika Lundy
- Extension Beef Program Specialist
- Iowa Beef Center - Iowa State University
- Email Erika Lundy
