Breeding Season Strategies From the Experts

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Breeding Season Strategies From the Experts


By Jaclyn Ketchum    |    

Editor’s note: Jaclyn Ketchum is a masters student studying Reproductive Physiology with Dr. Michael F. Smith in the Division of Animal Sciences at the University of Missouri. Ketchum summarizes an annual conference focused on applied reproduction in beef cattle and improving assisted reproductive technology.


 The 2018 Applied Reproductive Strategies in Beef Cattle Symposium was held in Ruidoso, New Mexico, August 29 and 30. This conference is organized by the Beef Reproduction Task Force, a multi-state extension effort with the following objectives: 1) Increase the successful implementation of protocols that synchronize estrus and ovulation in beef herds, and 2) Improve the understanding of methods to assess male fertility and how it affects the success of AI programs. Attendees included producers, AI industry personnel, veterinarians, and others with an interest in beef cattle reproduction. Below is a brief overview of a selection of the presentations. 

The meeting began with an overview of the physiological principles that underlie current protocols for synchronization of estrus and ovulation in beef cattle by Dr. Mike Smith, University of Missouri. Smith stressed the importance of understanding these principles to make informed decisions regarding the implementation of estrous synchronization protocols and to assist in deciding how to proceed when a protocol is not administered correctly. Smith was followed by Dr. Dave Patterson, University of Missouri, who discussed the currently available fixed-time AI protocols for heifers and cows and practical suggestions for the implementation of the protocols. Patterson emphasized, if executed properly, the protocols work and provide a powerful tool for increasing the proportion of heifers and cows that conceive early in the breeding season. Dr. Jordan Thomas, University of Missouri, discussed physiological differences in the response of Bos indicus compared to Bos taurus-influenced cattle to fixed-time AI protocols, which is relevant in the Gulf Coast region and Southwest part of the country. Further effort to optimize fixed-time AI protocols is warranted.   

Kansas State University Extension Beef Specialist Sandy Johnson discussed tools designed to aid producers with scheduling protocols for synchronization of estrus and ovulation as well as implementing timely reproductive and herd management practices. For example, the Estrus Synchronization Planner (Iowa Beef Center) is designed to assist in the selection and implementation of an appropriate estrous synchronization protocol. After selecting a protocol and entering required information such as breed type, number of head, and breeding date, the planner provides key dates and times that require action, estimated cost of implementing the protocol, supply list, and other helpful information.   

The planner can be found at: or if the producer plans to synchronize several groups of heifers or cows, the multi-group edition link is as follows: software.html. A mobile version of the planner can be found by typing into a browser on a mobile device. An additional tool that aids in timely management of a herd year-round is Management Minder which reminds producers of important dates and tasks that need to be completed. This tool can be found at and can be shared with employees. Planner


Wrapping up the foundational principles section of the symposium was Dr. George Perry, South Dakota State University. Perry emphasized when implementing synchronization and AI program, pregnancy success is only as strong as the weakest link. To increase the probability of success, heifers and cows should meet the following criteria by the time the protocol is implemented. Heifers should have attained an appropriate target weight and >50% of the heifers should have a reproductive tract score of 4 to 5 by four to six weeks before breeding. Postpartum cows should average 40 days postpartum (minimum ≥ 21 days postpartum at CIDR insertion), be in average body condition (≥ 5 at calving; 1 = emaciated and 9 = obese), and not experience significant weight loss after calving.

Time is precious, so when the option arises to reduce the number of trips through the chute, most producers take it. An example would be administering pre-breeding vaccinations at the start of a synchronization protocol. This saves time, but at what cost? Several studies conducted by Miller, Chiang, and Perry have reported negative impacts on pregnancy by vaccinating naïve heifers with a modified live virus (MLV) around time of breeding. Thus, an important variable to know is vaccination history. Are heifers naïve or non-naïve? According to Perry, “Females that have not been previously vaccinated are naïve while those that have been are non-naïve.”

You should also know what class of vaccine was administered. Recent research has reported that administering an MLV at 30 days or less pre-breeding can reduce AI conception rates even in non-naïve cattle. Chemically altered/inactivated vaccines (CA/IV) are considered safer and administering them closer to the start of the breeding season has not been reported to cause problems in non-naïve heifers.

Perry also points out that the efficacy of the class of vaccination is important to consider. Females that have only been exposed to CA/IV will have lower efficacy when exposed to BVD or IBR. Perry recommends heifers receive an MLV and their boosters early in life, then animals can be administered a CA/IV closer to the breeding season without worrying about reproduction or health concerns. Management practices associated with a female’s diet before and after breeding are important to consider. The general recommendation is to keep the animal’s diet consistent prior to and during the breeding season. In addition, changing the environment in such a way that heifers are moved from a confined environment pre-breeding to a pasture post-breeding leads to increased nutritional demand in addition to the increased activity of the heifers. When heifers have not had any previous grazing experience, they must learn how to graze on top of already increased nutritional demand, creating a situation that sets the heifer up to fail reproductively. 

Shipping stress associated with transporting cattle to summer pasture can negatively impact pregnancy rate if not completed within four days of AI. Shipping females between day five and 42 after AI exposes the developing embryo to stress that appears to alter the uterine environment in a harmful way, resulting in approximately a 10% decrease in pregnancy rates. A 6% decrease in pregnancy rates was observed when females were shipped on day 45 to 60 of pregnancy. The current recommendation is to ship females between day one and four of pregnancy. Transportation stress appears to affect the embryo while in the uterus but not in the oviduct. 

 Although many of the presentations were focused on the female, bull fertility, semen handling, and proper AI technique were also discussed by Dr. Joe Dalton, University of Idaho. Based on the 2009 NAHMS survey of beef operations, scrotal circumference was measured in only 16% of herds and only 27% of the herds had bulls semen tested. Dalton sited Chenoweth (2002), who reported for each $1 invested in bull breeding soundness exams (BSE), there is a $20 benefit. Furthermore, Dalton presented data showing only 82% of beef bulls were classified as satisfactory potential breeders. Dalton emphasized a BSE should be performed prior to purchasing a bull, every year, and if there is any concern related to a bull’s fertility. 

The Reproductive Task Force is encouraged by the progress being made in beef cattle adaption of reproductive technology. For more hands-on tips and resources, check out Applied Reproductive Strategies in Beef Cattle online ( or join the meetings August 20-21, 2019, in Knoxville, Tennessee.   Check out additional content on tReg for more summaries from the 2018 ARSBC meetings and links to helpful resources.


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