Now is the time to use estrous synchronization

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For many cow-calf producers, the spring calving season is likely in full-swing or coming to an end. Assessment of last year’s mating decisions has started, and development of a strategy for the approaching breeding season can begin. Although the focal point of most breeding season strategies is to determine which bulls will be added or subtracted from the line-up, it is equally as important to evaluate the method by which these genetics will be introducing in to the cow herd. Given the current yearly maintenance costs of the breeding herd hovering around $800/head and the sustained volatility of commodity markets, it is imperative that producers strive to implement genetics that allow for greater production with fewer inputs.

One potential way to increase production and minimize input is through the use of artificial insemination (A.I.) when used in conjunction with estrous synchronization. In a study published in the Journal of Animal Science in 2012, it was reported that cows submitted to a timed-A.I. estrous synchronization protocol had a return on investment that netted $49 more per cow exposed than cows which were only exposed via natural service. These monetary gains associated with use of estrous synchronization and A.I. are derived from 3 primary areas:

  1. Estrous synchronization protocols that incorporate a period of timed- A.I. ensure that all cows are given the opportunity to conceive earlier in the breeding season, resulting in a greater proportion of older, heavier calves at weaning./li>
  2. A.I. allows for introduction of proven genetics with increased EPD accuracies, thus potentially increasing pre-weaning average daily gains for calves born to A.I.
  3. Getting more cows pregnant to A.I. has the potential to reduce (but not eliminate) the number of bulls needed on-hand.

Although use of estrous synchronization and A.I. can be financially rewarding, given the number of synchronization programs available to select from as well as the substantial differences in implementation schemes, choosing the one that is correct for a specific farm or ranch can be a bit overwhelming. To assist producers in identifying which programs are a good fit for them, the Estrous Synchronization Planner (www.iowabeefcenter.org/estrus_synch.html) has been developed by the Iowa Beef Center in conjunction with the Beef Reproductive Task Force. This free Microsoft Excel-based program contains a current list of approved protocols for estrous synchronization that allows producers to compare labor and cost differences between protocols. In addition, the Estrous Synchronization Planner can assist producers in developing a calendar which outlines daily activities for the synchronization program selected, thus increasing protocol compliance and helping maximize pregnancy rates to A.I.

When choosing an estrous synchronization protocol, it is important to be mindful that some heifer based protocols require in excess of 30 days to execute from start to finish when using orally active progestins (melengestrol acetate, commonly referred to as MGA). So, be sure to plan ahead to guarantee the target breeding date is met. In addition, protocols using MGA demand that adequate bunk space is available and that feed is properly mixed to ensure cattle consume the necessary amount of MGA each day.

Selection of synchronization protocols that have some degree of estrous (heat) detection may minimize the number of injections needed, and has the potential to slightly improve conception rates to A.I. However, labor associated with heat detection, particularly at a time when many producers may be planting crops, might not contribute enough return on investment to justify the labor. Therefore, many producers have transitioned to estrous synchronization protocols which utilize a pre-determined A.I. period at the conclusion of the program. Although these protocols require an additional injection of gonadotropin releasing hormone (GnRH) at A.I. they ensure that all cows are inseminated and given the chance to conceive on the same day. Although timed-A.I. protocols may deliver slightly lower A.I. pregnancy rates than some estrous detection-based programs, the reduction in labor traditionally needed for estrous detection and extra handling of animals, as well as the added weaning weight resulting from timed-A.I. economically outweigh the disadvantages.

If considering a protocol that utilizes timed-A.I., it is also important that producers only synchronize the number of cows they are confident they can A.I. in a 4 hour window. For instance, if a protocol requires a period of time between prostaglandin administration and A.I. service that is 72 hours, breeding of the synchronized group could begin at 70 hours, but needs be finished by 74 hours post prostaglandin administration. The number of animals a producer or A.I. technician can inseminate in this time will vary based on skill set, facilities, and labor. Therefore, discreet judgment is required on the producer’s part if the greatest pregnancy success is to be obtained.

One question that often arises is how short the calving period may be in females synchronized for A.I. on the same day. This can be of particular concern in some herds where calving facilities, especially for first-calf heifers, are limited. A previous study reported that heifers subjected to, and which became pregnant to A.I. on the same day, had calves born across a span of 28 days with only 14% of the heifers calving on the most active day. Therefore, depending on a specific producer’s calving season and management scheme, careful synchronization planning should be implemented to ensure that calving rates do not exceed facility capacity.

Most importantly, to maximize the potential of estrous synchronization and A.I., it's vital that the synchronization protocol be strictly adhered to. Just as importantly, however, producers should select the protocol that best fits their operation based on labor, facilities, and management schemes. For further assistance in developing an A.I. and estrous synchronization program tailored to their farm or ranch, producers should work with a reproductive specialist in their area. A little bit of time spent now in planning a breeding season estrous synchronization program could dramatically enhance profit margins for years to come.

Source: Patrick Gunn, ISU Extension cow-calf specialist



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