Take a Planned Approach to Re-Enrolling Open Females into Your Breeding Program
Sarah Thorson, Beef Marketing & Education Manager, Genex
Even after putting forth great effort into following synchronization and timed artificial insemination (A.I.) protocols, one must realize not all cows will conceive from their first or subsequent inseminations. Research indicates 40 percent or less of all females will be pregnant following their first A.I. (Pursley et al., 1998). The most important question then becomes how to handle the large percentage of females that did not conceive.
One approach is to enroll females that have been diagnosed as open into a resynchronization program. Resynchronization is a strategy by which non-pregnant cows are quickly re-enrolled for a second or subsequent A.I. service. Resynchronization occurs immediately after pregnancy diagnosis (or may even start before) using an Ovsynch®-type protocol. Since the inception of timed synchronization protocols about 15 years ago, resynchronizing of non-pregnant cows has become a component of management plans allowing dairy producers to significantly improve cattle reproductive efficiency.
To realize the full benefits of resynchronization, a producer must have a systematic plan in place to identify and then resynchronize the non-pregnant cows thus reducing the interval between A.I. services, increasing A.I. service rate and improving profitability.
Pregnancy diagnosis - whether by blood testing, rectal palpation or ultrasound - is the first critical step to initiation of a resynchronization protocol. Striving for early pregnancy diagnosis makes sense, but caution should be exercised to minimize early embryonic mortality. A study (Fricke et al., 2003) has shown embryonic mortality contributes to reproductive inefficiency because fertility assessed at any point during pregnancy is a function of both conception rate and mortality.
The research conducted by Fricke et al., at the University Wisconsin (2003) has further shown pregnancy loss is higher during early gestation and then decreases as gestation proceeds. In assessing the most suitable resynchronization strategy, the study compared three time intervals between timed A.I. and the initiation of resynchronization. Pregnancy diagnosis was performed at 19, 26 and 32 days after timed A.I. The study showed that pregnancy diagnosis at day 19 after timed A.I. yielded the lowest pregnancy rate following resynchronization. Pregnancy diagnosis on day 26 and 32 yielded similar fertility post resynchronization but showed increased early embryonic death at day 26 compared to day 32. Pregnancy diagnosis 32 days post timed A.I. yielded the highest overall pregnancy rate. Overall, there was a $15 per cow advantage for initiating pregnancy diagnosis and resynchronization at 32 days post timed A.I. over 26.
The second critical step to realizing the full benefits of resynchronization is to have a proper resynchronization protocol plan in place. Different resynchronization strategies have been researched and shown to produce varying results. The biggest challenge for producers is to pick the best program that fits their dairy's routine, gets more cows pregnant and provides higher economic returns. Review and consider the application of these resynchronization program approaches:
The resynch program simply involves repeating Ovsynch once a female is diagnosed as open. With this protocol, pregnancy diagnosis should occur approximately 32 days after the first timed A.I. As a cow is diagnosed open, she receives an injection of GnRH. Seven days after the first timed A.I., Prostaglandin (PGF2∝) is injected. Then 48 to 56 hours later the second injection of GnRH is administered and timed A.I. occurs 12 to 24 hours later.
This is a more aggressive resynchronization strategy than the previously explained resynch program. In presynch resynch, GnRH is administered to all females seven days prior to pregnancy diagnosis. This GnRH shot does not harm the fetus of a pregnant cow; instead, it only serves as a jump start for resynchronizing open females. At the time of pregnancy diagnosis, cows deemed open are injected with PGF2∝ immediately. GnRH is administered 48 to 56 hours after the PGF2∝ injection. Insemination occurs 12 to 24 hours after GnRH is administered.
In the GGPG resynch program, the first GnRH shot is given 14 days prior to pregnancy check day. A second injection of GnRH is given seven days later. On pregnancy check day, all open cows are injected with PGF2∝. GnRH is administered again 56 hours after the PGF2∝ injection. Insemination is performed 16 hours later.
Double Ovsynch Resynch
Double Ovsynch resynch also includes giving GnRH seven days prior to pregnancy check day. On the day of pregnancy diagnosis, all open cows receive PGF2∝ followed by GnRH three days later. A second round of Ovsynch is started seven days later by injecting cows with GnRH. After another seven days, a PGF2∝ injection is given followed by a GnRH injection two days later. Finally A.I. is performed 24 hours cater.
As indicated by Chenault et al. (2003), in this program the EAZI-BREEDTM CIDR is inserted into open cows on the day of the pregnancy check. It is removed seven days later. At the same time, PGF2∝ is injected. GnRH is administered three days later and timed A.I. is performed.
The success or failure of any of these resynchronization protocols depends on how well they are implemented. The choice of which protocol to utilize varies based on total program cost, availability of labor, and facilities at the farm. Remember the outcome is cumulative, every step of the protocol counts.
Chenault, J.R., J.F. Boucher, K.J. Dame, J.A. Meyer and S.L. Wood-Follis. 2003. Intravaginal progesterone insert to synchronize return to estrus of previously inseminated dairy cows. J. Dairy Sci. 86:2039-2049.
Fricke, P.M., D.Z. Caraviello, K.A. Weigel, and M.L. Welle. 2003. Fertility of dairy cows after resynchronization of ovulation and three intervals following first timed insemination. J. Dairy Sci. 86:3941-3950.
Pursley, J.R., R.W. Silcox and M.C. Wiltbank. 1998. Effect of time of artificial insemination on pregnancy rates, calving rates, pregnancy loss, and gender ratio after synchronization of ovulation in lactating dairy cows. J. Dairy Sci.81:2139-2144.