Long breeding and calving seasons can mean extra time and labor costs for producers, but by synchronizing cows’ estrous, a producer can spend less time observing natural heats and subsequent breeding as well as reduce the time needed to observe calving 283 days later.
Dr. Tommy Perkins, a professor in the Department of Agriculture at Missouri State University, said cows must be prepared before starting the synchronization process.
“Cows on an increased plane of nutrition (increased body condition score) generally respond better to the synchronization process and subsequent conception,” he said.
Dr. Perkins said after cows are physically ready, producers must choose which method to use.  There are a variety of products available on the market to synchronize estrous in a cow herd.

Products to Plan Estrous
Melegesterol acetate (MGA) is a common feed additive given to a female for 14 days.   It actually suppresses estrous, and they come into estrous after being removed from the product after a 14-day feeding.  MGA is most often used on heifers.
Prostaglandins (lutalyse or estrumate) are injections given to females that will bring them into estrous.  The stage of their estrous cycle at the injection time determines if they will respond.  A two-injection method is used most often – cows are given a prostaglandin shot on Day 1 and another prostaglandin shot on Day 10 if they did not respond to the first injection. 
“A producer should breed all cows on observed standing heats following either injection.  This doesn't offer the smallest window for synchronizing all females, but it is cost effective,” he said.   “Special care should be used when using prostaglandins, as they can cause abortion in the pregnant female.”
Perkins said CIDRs (vaginal progesterone slow release insert) in combination with prostaglandins and gonadotropin releasing hormones (GnRH) have been effective in synchronizing cows.  The procedure includes depositing the CIDR on Day 1 and administering a GnRH shot, followed by removing the CIDR on Day 8 and administering a prostaglandin shot. 
“Most all of the cycling cows will respond to this regime; however, it is more costly and labor intensive than the other two options,” he said.

Follow Proper Protocols
Depending on the treatment used, a concentrated period of insemination can last from one to six days.  Producers should be conscientious to the procedures needed in the chosen synchronization method. 
“Don't take short cuts in the protocol and most importantly, be prepared,” Perkins said. “The labor and cost can be somewhat prohibitive if the producer is not prepared or does not have the correct facilities to complete the breeding task.”
Brett Barham, an assistant professor in breeding and genetics at the University of Arkansas Division of Agriculture, said estrous synchronization is practical for producers who are artificially inseminating cows because the cows will cycle closer to the same time, making it easier to more efficiently plan the required labor and time.  However, producers should be aware of the number of cows being treated.
“Producers who keep their numbers small and manageable will be more successful in the long run,” Barham said.  “If this is a producer’s first time synchronizing estrous, I usually recommend working with only 10 to 14 head at a time.”

Synching for Bull's Success
Barham said synchronizing estrous is also useful for producers using bulls on their cows.
“Producers should make sure to have enough bulls to service all of the cows.  A bull is usually not used to having every cow in heat at the same time and may not be successful by himself,” he said.  “Some producers overlook this detail and wonder why not all of their cows were bred.”
Estrous synchronization is a practical way to breed and calve the majority of a cow herd in the shortest amount of time. Barham recommends talking with a local extension agent or veterinarian before beginning estrous synchronization.
“There are many resources out there for producers who are interested in estrous synchronization, including extension services,” he said.  “Whatever method producers choose, following the correct protocol and getting sound advice are both keys to being successful.”


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