Determination of synchronization based on progesterone (P4) concentrations.

Cows were considered to not be synchronized if they had P4 2α, P4 > 0.7 ng/mL on Day of last GnRH, or P4若奶牛在末次促性腺激素释放激素（Gonadotropin-Releasing Hormone，GnRH）注射当日的孕酮（Progesterone，P4）检测结果为P4 2α、孕酮（P4）浓度＞0.7 ng/mL，或仅存在P4，则判定其未处于同步化状态。