Implementation of the Ovsynch program for timed insemination at certain stages of the estrous cycle (i.e., days 1-4 and days 13-17) resulted in reduced fertility. This led to the development of the Pre-Synchron/Ovsynch Program in which the Ovsynch program is initiated 12 days after the second PGF_2α injection of a pre-synchronization (i.e., PGF_2α given twice 14 days apart). This reproductive program has increased pregnancy rates to the Ovsynch program by ~ 13% and has been readily adopted by the dairy industry.

In an effort to further improve acceptance of Timed Insemination Programs, the Heat Synch program has been developed. The Heat Synch program incorporates the injection of Estradiol Cypionate (1 mg for cows and 0.5 mg for heifers) given at 24 h after the injection of PGF_2α of the Ovsynch program. Cows are pre-synchronized with two injections of PGF_2α(given 14 days apart), and the Heat synch program is started 12 to 14 days after the second injection of PGF_2α. Heat Synch involves the injections of GnRH and PGF_2α; given 7 days apart, injection of ECP 24 h after PGF_2α, and cows are inseminated at either 24 h after ECP (if in heat) or at 48 h after injection of ECP. Fertility trials indicate that Heat Synch and Ovsynch programs have comparable levels of fertility. Heat Synch offers the following advantages for producers: cows have good uterine tone at insemination, injections and insemination can be given at the same time of the day on their respective days of injection etc., and the program is less expensive due to the lower cost of ECP. This program also has been well received with dairy producers. It may be less effective than Ovsynch when used on anestrus cows.