Estrous synchronization (Proceedings)

Estrous synchronization is the manipulation of the reproductive cycle so that cows can be bred in a predefined interval. Typically, estrous synchronization has been used to facilitate artificially insemination (AI) by decreasing labor to detect estrus and to schedule breeding to specific days. However, the benefit of synchronizing estrus goes beyond just being able to AI cows. There are long term benefits to the calf crop that can make a synchronization program beneficial to bull bred herds also.

The first benefit is a condensing of the calving season. When we front load the breeding program with synchronization we will then front load the subsequent calving season. This can make the first 2-3 weeks of the calving season fairly intense but the remainder of the calving season will seem like a breeze. Producers that use off farm labor during calving can consolidate their costs into a shorter time frame. Downside of early intensive calving is that if something goes wrong it can really go wrong. Make sure your clients have the facilities to handle the activity and it may be beneficial to calve later in the year when the threat of a severe snow storm has abated.

Another benefit can be improved health of the calves in general. One of the biggest risks for calf diarrhea and summer pneumonia is having calves of various ages mixed together. The older calves will expose the younger calves to pathogens that their immune system cannot handle yet. A synchronized herd will have more calves the same age and fewer calves in the tail end of the calving season. Condensing the age of calves to within 30-45 days compared to 60 or 90 days can improve the health of calves.

Lastly there is a financial benefit when your clients sell their calves. When the cow herd is synchronized producers will be able to put together a bigger group of calves that are the same weight and age. Buyers will typically pay more for a uniform group of calves. Additionally, if more calves are born early in the calving season there will be an increase in weaning weights because the average age is increased.

There are enough different synchronization programs available that you will be able to find one that will work for your different clients management style. The Beef Reproduction Task Force has approved synchronization protocols for cows and heifers for either heat detection or timed AI programs. These protocols are published in the catalogs of the various semen suppliers. Additionally, a free estrus synch planner is available at http://www.iowabeefcenter.org/estrus_synch.html. The planner provides details on different protocols and will develop a calendar of the different steps required for each protocol. Specific protocols will be discussed at the meeting but since these can change veterinarians should review the approved protocols each year before implementing one.

For natural service traditional bull to cow ratios of 1:25 is sufficient even with synchronized cows. A study in Colorado several years ago demonstrated no difference in pregnancy rates between a 1:25 (83%) versus a 1:16 (84%) bull female ratio with synchronized heifers for a 28 day breeding season. However, yearling bulls probably are not capable of breeding synchronized cows compared to mature bulls. Bulls should have a breeding soundness exam prior to the breeding season to make sure they will be capable of servicing a large proportion of cows at one time.

Estrous synchronization may not be for every producer. Use of this technology generally requires skilled management and adequate facilities. Cows will respond poorly if not fed properly or if body condition is less than adequate. Level of herd health is also a factor, as many diseases cause reproductive failure.