by Dr. Jonathan DeClerck
In today’s seedstock business, standing still is equivalent to moving backwards. Whether flipping through sale catalogs, analyzing genetic trait trends, or admiring show ring champions, one thing is clear: Simmental cattle have made extraordinary progress over the last decade. The American Simmental Association has long been the home of progressive breeders who leverage science and technology to drive genetic advancements.
Unsurprisingly, the rate of genetic progress has accelerated with the adoption of embryo transfer (ET). As one of the most effective tools for amplifying the influence of superior cow families, ET offers incredible potential. However, its success depends on intensive management and attention to detail, as the variability of results can be significant.
Among the key challenges of a successful ET program is the performance of recipient females (recips). All too often, recips are cull cows removed from the herd due to poor reproductive performance or inadequate body condition. This creates a significant hurdle, as the industry’s most progressive genetics are often entrusted to cows with a history of reproductive challenges. Even when recips are among the most productive cows in the herd, proper nutritional management is critical to achieving successful pregnancies and maximizing the potential of embryo transfer programs.
Ramping up the Plane of Nutrition
Maintaining proper body condition scores (BCS) in recipient cows is critical for achieving successful reproductive outcomes. Like the rest of the cow herd, recip cows with optimal body condition are more likely to conceive and maintain pregnancies. It’s a familiar scenario at pregnancy check time — open cows are often the thinnest, as nutrient partitioning prioritizes maintenance and lactation over reproduction. Cows losing weight are notoriously difficult to breed. Ideally, recip cows should have a BCS of 5 to 6 on transfer day. However, in light of the recent drought affecting many regions, some cow herds are struggling to reach this benchmark.
Fortunately, research has demonstrated that even thin cows (BCS 4) can achieve reproductive success when placed on an increasing plane of nutrition. Consider this analogy: A young married couple might delay having a baby due to financial concerns, but a job promotion or pay raise—though not yet realized—might encourage them to start trying. Similarly, a recip cow on a steep nutritional “ramp-up,” with energy intake exceeding maintenance and lactation requirements, can often resume estrous cycling. A study by Dr. Spitzer at the University of Illinois highlighted this effect, showing that BCS 4 cows on an increasing plane of nutrition achieved a 92% pregnancy rate, compared to just 43% for cows on a level plane.
This “ramping-up” strategy is effective because increased caloric intake boosts insulin production, which not only aids in glucose and carbohydrate metabolism but also supports reproductive tissues, particularly the ovaries. Insulin-like growth factor (IGF-1), which is linked to the development of the corpus luteum, further illustrates why ramping up the plane of nutrition can drastically improve ET success rates.
One proven method to ramp up nutrition is the inclusion of supplemental fat in the diet. Fat is a calorically dense nutrient, containing 2.25 times more energy than carbohydrates, and provides additional reproductive benefits beyond its energy contribution. Fat contains cholesterol, a precursor for key reproductive hormones like estrogen, progesterone, and prostaglandins, which stimulate the estrous cycle and sustain pregnancy. Research by Dr. Reinaldo Cooke at Texas A&M has shown that supplemental fat enhances pregnancy recognition and accelerates embryonic development. While fat sources and quality vary, practical experience suggests that feeding approximately 1/2 pound of supplemental fat daily is sufficient to jumpstart the reproductive cycle.
Effective nutritional ramp-up programs should focus on high-energy rations, starting 30 to 50 days prior to ET and continuing for at least four weeks post-implantation. To ensure success, cows should remain on a consistent energy plane, avoiding sudden dietary changes that might disrupt uterine receptivity. Additionally, diets high in sulfur (often from distiller’s grains) should be avoided, as sulfur can antagonize copper absorption and reduce conception rates.
Adequate dietary protein is also crucial for supporting early embryonic development and maintaining uterine health. However, overfeeding protein (total ration protein ≥ 14%) should be avoided, as excess protein is converted into ammonia and urea, which can alter the pH of the reproductive tract and negatively impact conception rates.
The Importance of Sustained Nutrition
Proper brood cow nutrition is a continuous process that extends well beyond the successful completion of embryo transfer. Sustained nutrition plays a critical role in enhancing reproductive outcomes and significantly increases the likelihood of successful pregnancies. Once cows are confirmed bred, it is essential to avoid an “out of sight, out of mind” approach. Consistently meeting their nutritional needs ensures optimal performance throughout gestation.
Bolstering Performance with Vitamin and Mineral Supplementation
Mineral supplementation has long been regarded as the spark that ignites a successful nutrition program, and for good reason. Vitamins and minerals facilitate nearly every biological process or reaction in the body. Proper year-round supplementation can yield a 2:1 return on investment through improved conception rates, enhanced animal gain, and overall health.
In the cattle business, achieving the gold standard of a 12-month calving interval requires cows to breed back within 85 days postpartum. This is no small feat, especially as the act of calving often causes injuries to the reproductive tract that necessitate proper mineral supplementation for effective healing.
Not all trace mineral sources are created equal, and their bioavailability can vary widely. Oxides, for example, are virtually unavailable to the animal, while chlorides and sulfates offer better absorption. However, hydroxy and organic/chelated minerals are often the most bioavailable and therefore the preferred choice for optimizing reproductive performance. Trace minerals such as zinc, manganese, copper, and selenium play critical roles in reproductive hormone function and antioxidant defense. These elements directly influence key processes that ensure reproductive success.
In addition to minerals, vitamins E and A are essential for reproductive health. Vitamin E enhances embryo viability, while vitamin A supports a healthy uterine environment, both of which are critical for successful pregnancies. Including these micronutrients in a comprehensive nutritional program ensures the best possible outcomes for embryo viability and overall herd productivity.
Addressing Early Embryonic Loss Early embryonic death has a disproportionately large impact on ET and breeding programs, and its prevalence is often underestimated in the industry. Stress—caused by immune challenges, dietary changes, weather fluctuations, or improper cattle handling—is a primary factor contributing to this issue. When exposed to stress, cattle activate their innate immune system, a process that requires approximately one pound of glucose (blood sugar) every six hours. This energy drain often creates a caloric deficit, which can lead to early embryonic mortality.
Fortunately, several strategies can help mitigate these challenges. Supplementation with omega-3 fatty acids, for instance, has been shown to reduce inflammation and improve embryo survival rates. In addition, additives such as yeast cultures, prebiotics, and phytogenic compounds can stabilize rumen function, preventing unnecessary activation of the innate immune system. To further minimize stress, it is crucial to avoid sudden changes in feeding programs or moving recip cows until they have had adequate time to settle. If transportation is unavoidable, it should be conducted within the first two days following embryo transfer to minimize disruptions.
The Impact of Epigenetics on Cattle Performance
The importance of sustained nutrition extends beyond immediate reproductive outcomes, as it directly ties into the concept of epigenetics — the interaction between genes and the environment. Dr. Jared Decker and collaborators, in a recent presentation at the Beef Improvement Federation, estimated that epigenetics accounts for 3– 33% of variation in certain Expected Progeny Difference (EPD) traits. This phenomenon offers an explanation for why certain recipient cows consistently raise the best calves, regardless of the mating they carry.
The foundation of this phenomenon lies in fetal programming — the idea that a calf’s lifetime performance is influenced by environmental factors and nutritional events occurring before birth. Efficient recipient cows, which provide consistent and adequate nutrients to their developing fetuses, enable these calves to express their full genetic potential. This maternal nutrition and environment influence key traits such as muscle and bone mass, immune competency, fertility, and overall phenotype. By prioritizing sustained nutrition and minimizing stress throughout gestation, producers can significantly improve the genetic and phenotypic outcomes of their herds. These efforts not only enhance the success rates of ET and breeding programs but also contribute to long-term productivity and profitability. Investing in proper nutrition and management practices is a commitment to the future success of cattle operations and the advancement of the industry as a whole.
Going Forward
In a business where every breeding decision directly affects the bottom line, a strategic approach to nutrition is an investment in long-term success. Technologies like embryo transfer have been instrumental in driving the remarkable genetic advancements of the Simmental breed. However, the success of an ET program begins well before the procedure itself. By adopting a comprehensive and targeted nutritional strategy, breeders can optimize recipient cows, ultimately enhancing the efficiency and outcomes of their ET efforts. Proper nutrition isn’t merely an expense—it’s a foundational component that ensures the herd’s genetic potential is fully realized. While many factors influence the success of an ET program, recipient cow management is one area where breeders have direct control. Investing in a “ramp-up” nutrition program for recip cows may seem costly, but the potential return on investment is substantial. For optimal results, cows should be provided with a high-quality mineral program and maintained on a positive plane of nutrition for at least 30 days prior to ET. Additionally, reducing stress through proper cattle handling and sustaining an elevated plane of nutrition for 30 days post-transfer can significantly lower the risk of early embryonic mortality, improving overall program success.
Dr. Jon DeClerck is ASA’s incoming Executive Vice President and will begin in the role on July 1, 2025, following Dr. Wade Shafer’s official retirement. DeClerck worked as a Technical Consultant for Purina Animal Nutrition, and has advised stakeholders across the beef production cycle in New Mexico, Texas, and Louisiana, combining innovative research with practical solutions to help producers maximize profitability. Previously, he served as a lecturer and livestock judging coach at Texas Tech and Iowa State University, mentoring students and leading multiple national champion livestock and meat evaluation teams. DeClerck has been recognized as a national champion team coach, and is the recipient of numerous industry awards. Raised on a diversified farm near Aledo, Illinois, featuring a Simmental and commercial cow herd, Dr. DeClerck has a deep connection to the breed.
