NC_temp1201: Methods to Increase Reproductive Efficiency in Cattle
(Multistate Research Project)
Status: Draft Project
NC_temp1201: Methods to Increase Reproductive Efficiency in Cattle
Duration: 10/01/2027 to 09/30/2032
Administrative Advisor(s):
NIFA Reps:
Non-Technical Summary
Beef and milk production depend on females conceiving on schedule, delivering a healthy calf, and successfully rebreeding. Fertilization succeeds in roughly 90% of inseminations, yet only about half produce a calf. Most of that loss occurs in the first weeks of pregnancy, and each failure costs feed, labor, and time, delays or eliminates a calf, and results in otherwise productive animals being culled. With the U.S. beef cow herd at its smallest population since 1961 and calf values at record highsthe cost of infertility has never been so great.
For more than 40 years this group has collectively worked to tackle this issue, resulting on the development of estrous synchronization protocols widely adopted nationwide, including OvSynch in dairy cattle and the CO-Synch protocols in beef. Our goal is to further improve reproductive efficiency in both sectors. Our objectives are: (1) develop and refine breeding management systems and technologies, including tools that predict fertility before breeding decisions are made; (2) determine how biology, nutrition, environment, health, and management — in both females and males — govern whether pregnancy is established and maintained; and (3) deliver science-based recommendations to stakeholders through extension, industry meetings, and publications.
Pregnancy outcomes require thousands of animals across many climates, breeds, and systems before recommendations can be trusted, and no single station can generate such evidence. Beneficiaries include beef and dairy producers, veterinarians, breeding companies, extension educators, and students. This work advances USDA science priorities for agricultural production and farm profitability.
Statement of Issues and Justification
Statement of Issues and Justification
Need as Indicated by Stakeholders
Reproductive performance is the single largest determinant of profitability in cow-calf production and a primary driver of profitability in dairy production (Trenkle and Willham, 1977; Lamb et al., 2016). A female that fails to conceive during the breeding season consumes feed, labor, and facility resources for a full year without generating a calf, and is typically culled. Stakeholders in both industries consistently identify reproductive failure among their most costly and least controllable production problems.
The biology underlying this problem is well characterized and remains unsolved. Fertilization succeeds in approximately 90% of inseminations in heifers, beef cows, and moderate-yielding dairy cows, yet only 40 to 50% of single inseminations result in a calf (Diskin and Morris, 2008; Diskin et al., 2012). The majority of this loss occurs before day 16 of gestation, during maternal recognition of pregnancy and conceptus elongation, and is therefore invisible to the producer until a pregnancy diagnosis weeks later (Diskin et al., 2012; Wiltbank et al., 2016; Reese et al., 2020). This gap between fertilization and calving represents the largest single opportunity to improve productivity in the U.S. cattle industries.
The economic stakes have risen substantially since this project was last renewed. As of January 1, 2026, total U.S. cattle inventory stood at 86.2 million head, the smallest in 75 years, and the beef cow herd at 27.6 million head, the smallest since 1961 (USDA-NASS, 2026). Calf values have set records repeatedly over the same period (USDA-AMS, 2026). Each pregnancy generated is therefore worth more today than at any point in the history of this project, and each open female represents a proportionally larger loss. In the dairy sector, the combination of widespread sexed semen and beef semen use has produced a shortage of replacement heifers, with replacement heifer values reaching record levels (NAAB, 2026). In both industries, producers now have strong economic incentive to extract the maximum number of pregnancies from every breeding opportunity.
Global demand continues to reinforce this need. World population growth and rising per capita incomes in developing economies continue to increase demand for animal-source protein (Mensbrugghe et al., 2009; Sans and Combris, 2015), while agricultural land available to meet that demand remains essentially fixed (FAO, 2009). Increasing the reproductive efficiency of U.S. beef and dairy cattle allows greater output from a smaller national herd and is a direct route to meeting demand without additional land, feed, or water.
Originating more than 40 years ago, this project develops solutions to reproductive inefficiency in dairy and beef cattle by increasing the efficiency and predictability of reproductive programs. This is accomplished by evaluating the mechanisms that regulate reproductive processes affecting production efficiency and by disseminating reproductive management information to stakeholders in both industries.
Alignment with USDA Research and Development Priorities
This project directly advances the Secretary’s December 2025 priority of Increasing Profitability of Farmers and Ranchers by developing reproductive management systems and predictive tools that generate more calves and more marketable product per female exposed, reducing feed, labor, and replacement costs per unit of output (USDA, 2025). By accelerating the dissemination of superior genetics through artificial insemination and embryo transfer, the project also supports the priority of Expanding Markets and Creating New Uses of U.S. Agricultural Products, strengthening the competitiveness of U.S. cattle genetics in international markets.
Importance of the Multistate Effort
Beef
Advances in estrus synchronization and fixed-time artificial insemination (TAI) developed over recent decades have allowed producers to improve fertility, accelerate genetic improvement, tighten the breeding season, and shorten the calving season (Lamb et al., 2016). Despite this progress, adoption of assisted reproductive technologies (ART) in the U.S. beef industry remains low, and natural service remains the dominant breeding strategy. The most recent national survey found that only 11.6% of cow-calf operations used artificial insemination and only 7.3% used estrus synchronization, with 90.7% of beef females exposed to natural service alone (USDA, 2020). Only 37.5% of operations used any reproductive technology, and 58.7% operated without a defined breeding season (USDA, 2020). Currently recommended TAI protocols yield pregnancy rates that generally range between 40 and 60% (Lamb et al., 2016; Reese et al., 2020), so even among adopting operations, roughly half of the calf crop is not produced by AI. The rate at which superior genetics move through the commercial beef herd is correspondingly limited.
The consequences of low adoption are magnified by the current state of the national herd. With beef cow inventory at its lowest level in more than sixty years and heifer retention only beginning to increase (USDA-NASS, 2026), the reproductive performance of each retained female directly constrains the pace at which the industry can rebuild. Reproductive technologies that increase the proportion of females conceiving early in the breeding season produce older, heavier calves at weaning and more uniform calf crops, and they generate replacement heifers of known genetic merit born early in the calving season (Cushman et al., 2013).
International competitiveness is a further consideration. Unless commercial beef producers implement genetic improvement through reproductive management, the U.S. risks losing its competitive position to countries such as Brazil and Argentina, both leading destinations for U.S. beef genetics and both with rapidly expanding domestic use of artificial insemination and embryo transfer (ASBIA, 2025). Brazil now exceeds the United States in adoption of embryo transfer technology (Viana, 2025).
Multistate research and extension efforts to maximize the use of reproductive technologies are therefore warranted and will contribute to maintaining the genetic advantage of U.S. beef herds. An important driver of ART adoption is the efficiency and predictability of these technologies. Multidisciplinary basic and applied research to maximize the efficiency and predictability of these technologies will play an important role in the future of the U.S. beef industry.
Dairy
A reproduction revolution has occurred in the U.S. dairy industry over the past three decades. Phenotypic reproductive performance in U.S. Holstein and Jersey cows, and genetic merit for daughter pregnancy rate, reversed their historical declines in the early 2000s and have improved since (Norman et al., 2009). Although genetics, nutrition, and management have all contributed, the development of fertility programs (for our review see Carvalho et al., 2018) and their adoption by dairy farmers (Caraviello et al., 2006) have driven much of this change. Fertility programs for TAI, together with strategies for pregnancy diagnosis and resynchronization of ovulation, have increased both AI service rate and pregnancies per artificial insemination (P/AI) in high-producing Holstein cows relative to AI following detected estrus (Barletta et al., 2018; Santos et al., 2017).
The reproductive management landscape in the dairy industry has changed markedly since this project was last renewed. Genomic testing now allows producers to identify which females should generate replacements (Weigel et al., 2012; Lima et al., 2020), and breeding decisions have become correspondingly deliberate. Sexed semen accounts for approximately two-thirds of dairy semen sold domestically, and dairy operations now purchase more than 80% of all beef semen sold in the United States (NAAB, 2026). Between 2020 and 2025, beef-on-dairy semen sales rose 62%, and sexed semen sales rose 53.6%, while conventional dairy semen sales declined 47.4% (NAAB, 2026). The dairy herd has become a significant contributor to U.S. beef production, and reproductive management decisions made on dairy farms now influence beef supply.
This transformation has created new reproductive management questions. Aggressive use of beef and sexed semen has contracted the replacement heifer pipeline, and producers must now balance replacement needs against crossbred calf revenue (Ettema et al., 2017; Cabrera, 2022) under conditions in which both dairy replacements and beef calves carry historically high values. Sexed semen carries a fertility penalty relative to conventional semen (Maxwell et al., 1996; DeJarnette et al., 2009), which places a premium on synchronization protocols and insemination timing optimized specifically for its use (Bombardelli et al., 2016; Hall et al., 2017; Ketchum et al., 2021). Errors in these decisions compound over the three-year interval between conception and first calving.
The economic environment for dairy producers therefore rewards precise reproductive management more than at any previous point. For U.S. dairy farms to remain competitive, strategies to optimize reproductive management technologies must be evaluated, economically modeled, and transferred to the dairy industry.
Technical Feasibility of the Research
Over more than four decades, this project has contributed substantially to the development of breeding programs that optimize pregnancy rates, and has addressed the objections cattle producers commonly raise against adopting reproductive technologies. Information generated by this group led to the development of the OvSynch protocol in dairy cattle (Pursley et al., 1995, 1997) and its CO-Synch variants used in beef cattle. These protocols increase pregnancy rates in both beef and dairy females relative to control treatments because they induce ovulation in postpartum females that have not resumed estrous cycles by the end of the voluntary waiting period in dairy cows or by the onset of the breeding season in beef cows (Bisinotto and Santos, 2012). Protocols developed through this project are now the industry standard nationally and are recommended by the Beef Reproduction Task Force and the Dairy Cattle Reproduction Council.
Work completed during the current project cycle demonstrates that this group retains the technical capacity to address the objectives proposed here. Members have established the value of pre-synchronization strategies for improving response to fixed-time AI protocols (Bonacker et al., 2020a,b; Oosthuizen et al., 2020; Andersen et al., 2021; Mercadante et al., 2021); validated color Doppler ultrasonography for pregnancy diagnosis at day 20 of gestation, enabling substantially earlier resynchronization (Holton et al., 2021); characterized sire-side determinants of fertility, including the effects of overnutrition and body composition on semen quality and the paternal contribution to embryo development and quality (Fontes et al., 2025; Tariq et al., 2026); evaluated anogenital distance, reproductive tract score, and antral follicle count as pre-breeding predictors of fertility in both Bos taurus and Bos indicus-influenced females (Dias et al., 2025; Kaps et al., 2025; Schwartz, 2026); and characterized the reproductive tract microbiome and its relationship to fertility (Dias, 2023). Members have also examined temperament and animal handling during synchronization (Dias et al., 2022; Flax et al., 2026), immune activation and vaccination effects on ovarian and luteal function (Perry, 2025, 2026), and one-carbon metabolism in developmental programming (Crouse et al., 2025; Caton et al., 2025).
Several areas nevertheless require further investigation. The mechanisms underlying early embryonic loss remain incompletely defined, and no intervention reliably prevents it (Wiltbank et al., 2016; Reese et al., 2020). Predictive phenotypes for female fertility have been identified but not validated at the scale or across the range of environments required for producer recommendations (Dias et al., 2025; Schwartz, 2026). Sire contributions to fertility outcomes remain underexploited relative to female-side management (Bromfield, 2014; Fontes et al., 2025). The reproductive consequences of heat stress impose substantial economic losses on U.S. cattle production and are increasingly consequential in the southern United States (St-Pierre et al., 2003; Capela et al., 2025), yet are not adequately addressed by current protocols. Finally, sensor and data-driven approaches to reproductive management have advanced rapidly in the dairy sector (Valenza et al., 2012; Stevenson et al., 2014) but have not been systematically evaluated in extensive beef systems. Each of these areas is addressed by the objectives of this proposal.
The participating stations collectively maintain the research herds, laboratory infrastructure, and technical expertise required. Members hold appointments spanning basic reproductive physiology, applied reproductive management, animal breeding and genetics, veterinary medicine, agricultural economics, and extension, and have an established record of executing coordinated protocols simultaneously across institutions.
Advantages of a Multistate Effort
A foundational goal of this group is to generate statistically valid results that are applicable and relevant to dairy and beef farms across the United States. The primary endpoint in cattle breeding trials, pregnancy, is a binomial outcome, and detecting the differences of practical significance to producers, often on the order of five to ten percentage points, requires very large sample sizes. Hundreds to thousands of females across a range of environmental conditions, from Michigan and South Dakota to Texas and Mississippi, are required before recommendations can be issued with confidence for producers operating across the varied environments of the United States. No single experiment station can generate animal numbers of this magnitude within a reasonable timeframe.
Multistate structure also captures the biological and management variation that determines whether a recommendation generalizes. Breed type, in particular the contrast between Bos taurus and Bos indicus-influenced cattle, climate, forage base, herd size, and labor availability all modify the response to reproductive interventions (Fernandes et al., 2001; Fontes et al., 2019). A protocol validated only in temperate Bos taurus herds may fail under subtropical conditions or in Bos indicus-influenced females. Testing simultaneously across stations distinguishes genuinely robust recommendations from location-specific results.
Equally important, fertility is not a single trait but a multifactorial phenotype, determined jointly by ovarian function, oocyte and embryo competence, the uterine environment, semen quality, nutrition, immune status, thermal load, and the management decisions surrounding insemination. No single investigator or discipline can account for all of these determinants. The multistate structure assembles expertise in reproductive physiology, endocrinology, animal breeding and genetics, nutrition, veterinary medicine, microbiology, biostatistics, agricultural economics, and extension, allowing the same fertility outcome to be interrogated simultaneously from complementary perspectives and allowing each station to contribute the component it is best equipped to address.
This group has collaborated on numerous multistate projects to provide results with increased statistical power, with several publications representing the collaboration of at least six experiment stations. During the current cycle, members have jointly secured multiple multi-institutional competitive awards, including several USDA-NIFA AFRI grants, demonstrating that the collaborative structure attracts external investment beyond Hatch funds. Hatch support is used principally to maintain the coordinating infrastructure, standardize protocols and data collection across stations, and generate the preliminary data that make competitive proposals successful. The group also collaborates in the development of extension and outreach strategies to enhance adoption of breeding programs in both industries.
Potential Impacts from this Combined Effort
Previous work from NC1201 has already produced significant impacts in both the beef and dairy industries, and the efforts of this group have contributed directly to the current level of reproductive technology use in U.S. cattle. Protocols developed through this project are used on operations nationwide and are the basis of the recommendations published by the Beef Reproduction Task Force and the Dairy Cattle Reproduction Council.
Successful completion of the proposed work will increase the number of pregnancies established per breeding opportunity, increase the proportion of females conceiving early in the breeding season, and reduce pregnancy loss. In beef systems, shifting conception earlier increases calf age and weight at weaning and improves calf crop uniformity (Cushman et al., 2013). At current calf values, modest improvements in the distribution of conception dates translate into substantial increases in revenue per cow exposed, and aggregated across the national cow herd represent impacts measured in hundreds of millions of dollars annually. In dairy systems, improved reproductive efficiency reduces days open, lowers involuntary culling for reproductive failure, and allows producers to meet replacement needs while maximizing the value captured from beef-on-dairy matings (De Vries, 2006; Cabrera, 2022).
Fertility is the principal driver of ART adoption, because the return on investment in these technologies rises as conception rates rise. Improvements in the efficiency and predictability of reproductive technologies are therefore expected to increase adoption itself, extending the benefit beyond operations already using these tools. Predictive tools that identify females likely to conceive before breeding decisions are made will allow producers to allocate semen, labor, and replacement resources more efficiently. Producing more calves and more milk from a smaller national herd reduces the land, feed, and water required per unit of output, ultimately improving the efficiency of beef and dairy production. The research and outreach proposed here address these issues directly, and further detail is provided in the Methods and Outreach Plan sections of this proposal.
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