This document summarizes different methods of estrus synchronization in cattle, including shortening or prolonging the luteal phase using hormones like progesterone, prostaglandin F2α, and GnRH. It discusses the principles and limitations of estrus synchronization, and explains common protocols like Ovsynch and CIDR-PG that involve administering these hormones at specific time intervals to induce ovulation and allow for timed artificial insemination without detection of estrus. Examples of synchronization methods for cycling and non-cycling cows are also provided.