NC1038: Methods to Increase Reproductive Efficiency in Cattle (NC1006)
Statement of Issues and Justification
The need as indicated by stakeholders. The Food Animal Integrated Research Symposium (FAIR 95) identified the need to increase efficiencies of producing food from animals as a primary objective for future animal research. One of the key research areas with this objective was to improve scientific understanding of reproductive mechanisms. Since FAIR 95, FAIR 2002 was convened as the second national conclave to establish consensus on animal agriculture research and education priorities for the 21st century. Six goals were established for FAIR 2002, each with its own set of objectives. The first of those goals was to strengthen global competitiveness and develop systems to keep U.S. animal agriculture competitive for the 21st century. Objective 1 of that goal is to enhance production efficiency and economic strategies at the farm and ranch level. To partly achieve this objective, the report indicates that research on different farming systems is needed to achieve efficiencies in reproduction. The NC-1006 committee is a long-standing group that has contributed greatly to the increase in reproductive efficiency of cattle since its inception in the early 1970's. Its long-term goal is methods to increase reproductive efficiency in cattle which has been and continues to be consistent with the recent consensus goals set forth by FAIR 2002.The importance of the work, and what the consequences are if it is not done. Estrous synchronization and artificial insemination (AI) are reproductive management tools that have been available to beef and dairy producers for over 30 years. In beef cattle, manipulation of the estrous cycle has the potential to shorten the calving season, increase calf uniformity, and enhance the possibilities for utilizing AI. Artificial insemination allows producers the opportunity to infuse superior genetics into their operations at costs far below the cost of purchasing a herd sire of similar standards. These tools remain the most important and widely applicable assisted reproductive technologies available for beef cattle operations. Initial programs failed to address the primary obstacle in synchronization of estrous, which was to overcome puberty or postpartum anestrus. Current research has focused on the development of methods that effectively synchronize estrous in postpartum beef cows and replacement beef heifers by decreasing the period of time over which estrous detection is required, thus facilitating the use of timed artificial insemination (TAI). This new generation of estrous synchronization protocols uses two strategies which are key factors for implementation by producers because they: 1) minimize the number and frequency of handling cattle through a cattle-handling facility; and 2) eliminate detection of estrus by employing TAI. Results from this new generation of work should enhance the use of AI in beef cattle.
Unless owners of commercial cow herds aggressively implement genetic improvement through reproductive management, the U.S. will lose its competitive advantage in high quality beef production. International players that are more technically astute and competitively advantaged will position themselves to dominate the production and sale of beef worldwide.
Aggressive improvement in AI service rate in lactating dairy cows comprises three strategies that can be implemented early during the AI breeding period: 1) submit all cows for first postpartum AI service at the end of the voluntary waiting period (VWP) rather than waiting for cows to express estrus, 2) identify nonpregnant cows early after AI, and 3) aggressively return cows failing to conceive to first AI service to second and subsequent AI services. Traditionally, dairy managers had to rely on visual detection of estrous behavior, which is inefficient due to poor detection and expression of estrous behavior, to submit their cows for AI. The development of Ovsynch, a hormonal protocol that synchronizes follicular development, luteal regression, and ovulation thereby allowing for TAI without the need to detect estrus has radically changed reproductive management by providing dairy managers a practical and effective tool for improving AI service rate. Subsequent modifications of the Ovsynch protocol including presynchronization (i.e., Presynch), which involves two injections of PGF2± administered 14 d apart with the second PGF2± injection administered 12 to 14 d before initiation of Ovsynch and increases conception rate to TAI by 10 to 12 percentage points compared with Ovsynch alone. Refinement and improvement of systematic synchronization systems for submitting cows for first postpartum AI may further improve reproductive efficiency in lactating dairy cows.
In dairy cattle, research has demonstrated that anovulation is an increasing problem in lactating dairy cows. For example, in previous joint research on lactating dairy cows by the NC-1006 committee, we found greater than 26% of lactating dairy cows were anovulatory near the end of the voluntary waiting period. Recent studies by NC-1006 researchers that were discussed at our most recent technical committee meeting have continued to confirm a similarly high percentage of anovulatory cows based on multiple blood samples and multiple ultrasound evaluations of the ovaries. Thus, it seems clear that anovulation is a more significant problem in lactating dairy cows. Modifying the Ovsynch protocol to synchronize the time of ovulation in lactating cows may substantially further reduce labor inputs for reproductive management; however, it may be possible to improve fertility with this treatment (one of the purposes of the current proposal).
Although use of Presynch/Ovsynch and TAI for improving service rate to first AI reduces the impact of poor detection and expression of estrus, systematic strategies to identify and resynchronize nonpregnant cows (i.e., Resynch) are only beginning to be developed and evaluated. Because conception rates of high producing lactating dairy cows average 40 % or less, 60 % or more of cows that receive TAI fail to conceive and, therefore, require a resynchronization strategy to aggressively initiate subsequent AI services. Coupling a nonpregnancy diagnosis with a management strategy to rapidly reinitiate AI improves reproductive efficiency by decreasing the interval between AI services, thereby increasing AI service rate. Development of management strategies to identify and resynchronize cows failing to conceive to TAI is a critical step toward improving reproduction in lactating dairy cows.
The technical feasibility of the research. During the last 15 years, the NC-1006 project has contributed greatly to the development of several breeding programs to maximize pregnancy rates. These successes directly address the objections or reasons given by cow-calf producers for not adopting reproductive technologies. Information accrued by our group led to the development of the Ovsynch protocol and its variations (i.e., the Cosynch protocol, progestins + the Ovsynch protocol) used in beef cattle. These protocols generally increased pregnancy rates beyond controls because in both dairy and beef cattle, they induce fertile estrus and ovulation in postpartum cows that have not resumed estrous cycles by the end of the volunteer waiting period (dairy cows) or at the onset of the breeding season (beef cows). In the last 8 years, we tested the efficacy of adding progesterone to the Ovsynch protocol in lactating dairy cows. This experiment was replicated at seven (IL, KS, IN, OH, MI, MO, and WI) of the experiment stations involved in NC-1006. In beef cattle, the experiment was replicated at four (IL, KS, MN, and MO) of the stations. All of the above studies have been published in refereed journal publications.
More recently (our current projects), two additional studies have been completed in dairy (six stations) and beef (three stations) that are in the process of data summarization and publication. Therefore, the NC-1006 group has demonstrated the capability to coordinate, conduct, and publish experiments designed to improve fertility in dairy and beef cattle.
The advantages for doing the work as a multistate effort. Our past three NC-1006 projects have received considerable national attention and acceptance by producers, and it is the aim of the current project to improve fertility and ease of adoption of the tested developments. The multi-state collaborations planned in this project will provide new information applicable to beef and dairy producers and additional stakeholders. A strength of the multi-state collaborations is that they increase the power of the results and demonstrate national applicability. In addition, individual members of the NC-1006 have additional strengths and available laboratory expertise that strengthen our collaborations.
What the likely impacts will be from successfully completing the work. Beef producers have been slow to adopt these technologies into their production systems. Several factors, especially during early development of estrous synchronization programs, may have contributed to the poor adoption rates. Additionally, these programs failed to manage follicular waves, resulting in more days during the synchronized period in which detection of estrus was necessary. This ultimately precluded fixed-time AI with acceptable pregnancy rates. More recent developments focused on both corpus luteum and follicle control in convenient and economical protocols to synchronize ovulation. These developments will facilitate fixed-time AI use, and should result in increased adoption of these important management practices.
In dairy cattle, it seems clear that anovulation is a more significant problem in lactating dairy cows. Modifying the reproductive management protocols to synchronize the time of ovulation in lactating cows may substantially further reduce labor inputs for reproductive management; however, it may be possible to improve fertility. Development of resynchronization strategies to submit cows failing to conceive to first postpartum AI will further improve reproduction in lactating dairy cows.
JUSTIFICATION Reproductive inefficiency is one of the most costly and production-limiting problems facing both the dairy and cow-calf industries. For example, in six midwestern states that comprise the Heart of America Dairy Herd Improvement Association, 17.4 % of the dairy cows were culled because of reproductive failure. It was only exceeded by death (18.2 %) as the leading cause of culling (Heart of America Annual DHIA Summary). Similar statistics are reported by other DHIA organizations in the U.S.
Cull beef cow sales makeup 15 to 20 % of cow-calf herd total income (NAHMS, 1997). Over 27 % of beef cows are culled because of reproductive failure or reproductive problems. Based on numbers of operations, that percentage is 34 % of all cull cows. Further, these percentages increase with herd size: < 50 cows (16 %), 50 to 99 cows (30 %), 100 to 299 cows (51%), and > 300 cows (69 %). Only the western region (46 %) has greater culling for reproductive failure than the north-central region (37 %). The NAHMS survey concluded that "by optimizing reproductive performance, producers can decrease forced culls" (i.e., cows sold for involuntary reasons).
Losses that occur because of reproductive failure are partly due to mismanagement of resources and the lack of adoption of appropriate technologies to sustain greater reproductive efficiencies. In the 1997 NAHMS survey of beef cattle producers, questions were posed regarding use of various reproductive technologies on ranches. Of the 1,190 producers surveyed, AI was used by only 13.3 % of the operations; pregnancy palpation by only 34.5 %; and estrus synchronization by 11.9 % of operations. Of interest to our NC-113 committee's long-term objectives were the reasons why estrus synchronization was not employed on those cow-calf operations surveyed. Their reasons were: "it doesnt work" (2 %), "time and labor issues" (36 %), "lack appropriate facilities" (8 %), "cost" (13 %), "too complicated" (20 %), and "other" reasons (21 %). It was likewise interesting that those similar reasons were given, almost to the percentage point, for why those operations had not adopted the use of AI. Therefore, it is imperative to continue developing mechanisms to enhance reproductive efficiency in cattle, through basic and applied research outlined in current objectives.
The long-term goal of this proposal is to develop methods to increase reproductive efficiency in cattle. This Specific Aim long-term goal will be addressed through the two Objectives below.
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