Choosing and Using Estrous Synchronization Protocols.

 By Jaclyn Krymowski.

 Advancements in reproduction and endocrinology have allowed producers to use multiple procedures and methods of manipulating a cow’s estrous cycle for enhanced efficiency. The dairy industry has embraced these technologies enthusiastically with the beef sector not far behind.

Contrary to some misconceptions, estrous synchronization isn’t only beneficial for large-scale enterprises. It can also be a valuable boon to small and mid-sized operations, both in the commercial cow-calf and seedstock sectors.

Even when not coupled with other reproductive technologies, estrous synchronization can help shorten calving intervals and the breeding season, allowing calf crop birthdates to be more uniform. For any herds interested in pursuing any sort of artificial insemination and embryo transfer, mastering this technique is essential.

While beneficial, choosing the right mode of synchronization can be difficult. There are many offerings on the market, and more are sure to come, making it challenging to find the most practical and cost-effective protocol for any particular herd.

A look at the endocrinology
Before exploring synchronization specifics too deeply, let’s examine the basic reproductive processes and hormones at play.

In a cow’s cycle, the primary hormone involvement comes from progesterone, prostaglandin, gonadotropin releasing hormone (GnRH), follicle stimulating hormone (FSH) and luteinizing hormone (LH). All of them can be introduced artificially, but different protocols may use more or less of them while relying on the cow’s natural cycle.

Progesterone is what maintains a pregnancy after conception, with prostaglandin being what starts a new cycle and induces a new ovulation. Prostaglandin is the hormone that terminates a current cycle when no conception takes place.

Progesterone levels directly impact gnRH and its own levels impact both FSH and LH. Follicle stimulating hormone sounds just like what its purpose should be. It assists in the development of follicles to be released from the ovary. FSH is also heavily utilized for timing embryo transfers. Finally, luteinizing hormone surges to allow the dominant follicle to ovulate from the ovary.

Implementing Synchronization
The Alabama Cooperative Extension System provided three estrous synchronization programs that can work well with the cow’s normal estrous cycle in an article titled Estrus synchronization and artificial insemination programs for beef cattle. One method simply uses a series of prostaglandin injections to reduce the corpus luteum to allow for a standing heat.

Another program uses the natural progesterone or synthetic (referred to as progestin) in a CIDR insert to release the drug internally. It could also be incorporated by feeding melengestrol acetate. This second method prevents heat from occurring while the presence of progesterone, or progestin, is present. It is a popular method within the beef industry, but the additional trips through the chute needed to insert the CIDR, remove it, administer shots and breed (if doing AI) should be noted.

Lastly, a third method incorporates both GnRH and prostaglandin injections. A prostaglandin shot is administered followed by GnRH 48 hours later.

Remember that there may be some restrictions and holdbacks in trying to implement these programs with any given program. Management is also essential to the success of any protocol, both from an administration standpoint but also watching for subsequent heats and breeding.

It should be noted that overall poor herd management (especially in terms of nutrition and health) can be detrimental to any synchronization program. Poor body condition scores - both on the high and low ends of the spectrum - are often factors in failed breedings.

With multiple steps involved in most synchronization processes, it can be helpful to limit how many hands are involved in the process. Likewise, any involved employees should be trained thoroughly, understand the process and be excellent observers and recordkeepers. (Another common reason synchronizations programs might fail is due to improper heat detection.) In many cases, managers may find it most efficient and affordable to simply outsource all synchronization measures.

Successful programs
Successful synchronization programs consider the bigger picture of what calving season should look like. How strict a calving window needs to be may help dictate what type of protocol is used and may put problematic breeders on the cull list.

This pre-planned calving window takes many details into account. It should envision the age at which calves will be sold or retained and fit neatly with other aspects of herd management.

Operations that have not had narrow calving windows in the past might consider ways to improve management to take full advantage. More uniform calf crops are likely to have fewer losses, especially when management is smoother. It also makes vaccination protocols, weaning and feeding much less stressful on people and animals. Similarly aged calves are much more likely to have better nutrition management (especially with group feeding) and marketability.

Other considerations
In his article for the University of Nebraska-Lincoln, Benefits of estrous synchronization, extension educator Brent Plugge stated: “One consideration when choosing an estrus synchronization protocol is determining if sufficient labor and facilities are available to successfully implement the protocol.”

Determining any synchronization cost is vital along with the resources available. If you have the equipment and protocol in place but don’t have the qualified help, it can render an entire program useless.

Along with being able to implement a program is the cost. Cheaper methods are usually less effective and are more time-consuming, Plugge notes.

Estrous synchronization is currently used with many producers to tighten the calving interval and can lessen the time spent watching them, along with creating a more uniform calf group. Uniform groups can be beneficial for the market but are also attractive to feedlot producers and as replacement animals for your own herd.

Likewise, note that synchronization programs can be ineffective if there is excessive stress in addition to the other management practices that can impact their physical health.

Among the considerations that come with selecting a protocol are the whole team’s experience and capacity to handle these changes.