A recent research trial done by the University of Wisconsin, at Dr. Milo Wiltbank’s lab, (Souza et al., 2008) has shown promising fertility improvements following the use of the Ovsynch program in lactating dairy cows. The Ovsynch program is a sequence of hormonal treatments that combines gonadotropin releasing hormone (GnRH) and prostaglandin (PGF2α) to synchronize the time of ovulation in bovines allowing for timed artificial insemination (TAI).
Ovsynch protocol has been shown to increase service rates and improve reproductive efficiency in dairy herds. However, Ovsynch has some limitations when used in cows that are either not cycling or in cows that are not in the ideal phase of the estrous cycle at the beginning of the program. Therefore, several experiments tried to implement prostaglandin injections used at 14 days apart as pre-synchronization treatments to ensure that most of the cows were at the right stage of the reproductive cycle when Ovsynch starts (day 5th to 10th of the cycle).
According to the traditional presynchronization system, Ovsynch injections must begin 12 to 14 days following the last PGF2 treatment. Most of these trials observed improvements (of about 5 to 10% points increase in conception rate) in the first postpartum A.I. when prostaglandin treatments were used prior to Ovsynch.
However, these PGF2α treatments cannot induce cyclicity in anovular cows (animals with follicles > 10mm without CL). It is important to mention that anovulatory condition is very common in high producing herds at the end of the voluntary waiting period in the United States – normal incidence ranges from 20% to 30% in lactating cows around 60 days in milk (DIM). In other words, the regular pre-synchronization with two PGF2α does not seem to be effective to pre-synchronize anovular cows. In addition, there is a high dispersion of ovulations following a PGF2α treatment (ovulations occur within 3 to 7 days after PGF2α). Such high variation can produce follicles of different sizes when the Ovsynch protocol begins, which in turn might reduce ovulatory response by the first GnRH injection.
In order to overcome these limitations of the regular pre-synchronization strategy with two PGF2α injections, a new pre-synchronization system – called Double-Ovsynch – has been developed recently by University of Wisconsin researchers. This new pre-synchronization is named Double-Ovsynch because an Ovsynch protocol is used during the pre-synchronization period instead of two PGF2α injections.