LEGENDS OF FEEDLOT NUTRITION
Honor, recognize and memorialize
The purpose of the Legends of Feedlot Nutrition is to honor, recognize and memorialize those who have contributed to and who have had a profound and lasting impact on the feedlot industry as it relates to innovation, leadership, advancement, service, and education in the area of feedlot nutrition.
Legends of Feedlot Nutrition was established in 2016. The PNC Past President leads the process each year with the assistance of the PNC Executive Committee and LOFN selection committee.
Legends of Feedlot Nutrition nominations can be made by any member of PNC. Honorees are selected from three categories for their contributions to the feedlot industry:
- CONSULTANT
- ACADEMIA/EXTENSION
- ALLIED INDUSTRY
2025 HONOREES

John R. Brethour
John R. Brethour was born Sept. 30, 1934, in northwest Riley County, Kansas (40 miles from Manhattan). His farm life was without electricity or indoor plumbing. He attended a nearby one-room schoolhouse, then high school in Clay Center. John earned a bachelor’s degree in animal husbandry at K-State and a master’s degree in animal nutrition at Oklahoma State University under Dr. A.D. Tillman.
In 1957, John became the beef cattle research leader at K-State’s Agricultural Research Center in Hays. He was ever enthusiastic about his research and the benefit of using science to help cattle producers be profitable and competitive. John was an exceptional man with respect to intellect, relevancy, dedication, and productivity. His research was unprecedented in the use of ultrasound to monitor growth of finishing cattle. In addition, he developed his own computer processing algorithms to optimize carcass quality and yield outcomes. John’s ultrasound image analysis algorithms ultimately received U.S. patents. He successfully demonstrated the ability of ultrasound to sort cattle into ideal outcomes with multiple wins in beef carcass contests and via the adoption of his methods by the cattle feeding industry.
During 47 years, his research programs involved many additional areas: ruminant nutrition; feed evaluation, storage and processing; new livestock systems design (intact males and single-calf heifer); animal behavior; growth promotion; cow-herd management; breed evaluation; and reproduction. John helped show that a robust original-research program could be conducted off-campus. He preferred the branch stations to the main station on the campus of a land grant university. He loved it’s environment situated among the producer clientele and in the heart of the industry the branch station was created to serve. He was a research pioneer in the nutritional value of grain forage sorghums and wheat; ultrasound technology for the cattle industry to estimate intramuscular fat and predict future carcass merit; and adjusting cattle performance to final carcass weight.
John was a founding member of Cattle Performance Enhancement Company (CPEC).
Some of John’s honors and awards include the following:
- 1980: Distinguished Nutritionist, Distillers Feed Research
- 1989: Outstanding Achievement in Grain Sorghum Utilization, National Grain Sorghum Producers Association.
- 1991: Grand Champion in the Garden City Beef Empire Days Carcass contest. 1997: Distinguished Alumnus Award. KSU Agricultural Alumni Association.
- 1999: Grand Champion in the Denver Stock Show Carcass
- 2001: Grand Champion in the Garden City Beef Empire Days Carcass
- 2003: “Best of the Breeds” national contest ($100,000 prize) which validated ultrasound research for identifying superior animals upstream in the production (Of 140 contest entries, the top eight were selected with John’s ultrasound technology.)
- 2004: Beef Top 40- the 40 most influential people in the beef industry in 40th anniversary edition of Beef Magazine.
- 2006: Regional winner of the National Beef Cattleman’s Vision award; Livestock and Meat Industry Council “Stockman of the Year” award.
- 2013: Top 50 Industry Leaders- Beef
John Raymond Brethour married Carol June Thomas August 16, 1964 in Lake City, Fla. They had one son, John R. Brethour Jr.. John Brethour passed away at his home in Hays Kansas, May 29, 2007.

Gerald W. Horn, Ph.D.
Dr. Gerald W. Horn grew up in West Texas and earned his B.S. degree (1966) from Texas Tech University and M. S. (1968) and Ph. D. (1971) degrees from Purdue University. He was a member of the faculty at the University of Georgia for 4 years before joining the Department of Animal Science at Oklahoma State University (OSU) in January 1975. He taught 3 courses to veterinary students at the UGA and conducted research on the role of gastrointestinal hormones in the pathophysiology of ruminal lactic acid acidosis, and endotoxemia and the “sudden death syndrome” of feedlot cattle.
Soon after joining OSU, he recognized the unique and economically important role of wheat pasture for growing cattle in the southern Great Plains. He provided vision and leadership for developing a first-of-its-kind facility in the U.S. that was transformational for developing a multidisciplinary research and education program focused on dual purpose wheat. He devoted much of his career toward increasing the biological efficiency and profitability of these cattle. Finishing performance and carcass characteristics were measured when possible. Collectively, this research undergirds most modern nutrition and management practices for growing cattle on wheat and other small grains pasture in the U.S.
With the excellent collaboration of Drs. Clint Krehbiel, Phillip Lancaster and David Lalman, the focus of this research shifted in 2000 to a series of “system” studies of the predominant stocker/grower programs in the southern Great Plains. Traditional feedlot performance and carcass data were collected and concomitant fundamental studies focused on marbling development and understanding the physiological bases for differences in finishing performance were conducted.
Dr. Horn taught 6 different courses (2408 students) to undergraduate, graduate or veterinary students during his tenure at the OSU. His flagship courses were Advanced Ruminant Nutrition for graduate students taught from 1975-2015 and Stocker and Feedlot Cattle Management which he developed as a new course in 1992 and taught it every spring through 2016. He served as coordinator of the Animal Science Graduate Program for 16 years, and as major advisor of 38 graduate students and member of the graduate committees of 67 additional graduate students.
Dr. Horn has authored or co-authored 117 refereed journal articles, 203 abstracts at scientific meetings, 196 research reports of the Oklahoma Agriculture Experiment Station, and 85 papers in conference proceedings. He has been a member of the ASAS since 1971, ARPAS since 1975 and the PNC circa 1985. Dr. Horn received the ASAS Animal Management Award (1998), ASAS “Fellow” Award (2008) and the ASAS Southern Section Distinguished Service Award in 2016.
Dr. Horn is a leader by example and models professionalism and excellence in all his endeavors. He views the students he mentored as his most rewarding and signal legacy to the beef cattle industry. Many of them are in leadership positions in the feedlot and allied industries, academia or farm/ranch enterprises in the U.S., Mexico, Argentina and Uruguay.
Gerald and his wife, Chris, reside in Stillwater, Oklahoma and will celebrate their 55th wedding anniversary this coming August. They have 2 grown daughters and 2 grandsons.

Terry L. Mader, Ph.D.
Terry Mader was raised on a Northwest Kansas wheat farm, while showing Hereford cattle at the county and state fairs. Dr. Mader earned his B.S. in Feed Science and Management from Kansas State University and his M.S. and Ph.D. in Animal Nutrition from Oklahoma State University (OSU). Dr. Mader is Professor Emeritus at the University of Nebraska, Department of Animal Science. Prior to obtaining his degrees at OSU, Dr. Mader worked as a manager for an integrated farming operation and a grain and feed milling company.
During his academic career, Dr. Mader developed an internationally recognized research and outreach program addressing problems and concerns affecting the feedlot industry, including implant/growth promoting strategies, feed resource and facilities management, and managing environmental stress. Early efforts were devoted to developing birth to slaughter growth promoting strategies, which matched product dosage/potency to the animals’ stage of production. Research efforts evolved into assessing the interaction of growth promotant and season (heat vs cold) of the year. Additional studies were pursued, including effects of dietary components, feed additives, facilities management, and pen surface conditions on animal comfort/discomfort under hot and cold environmental conditions. Research demonstrated that increasing fiber level in high concentrate feedlot diets actually lowers body temperature under heat stress, due to poor fiber digestion. Also, recently published data demonstrated a high correlation between feedlot soil temperatures and cattle water consumption (winter and summer). Among seasons pen surface temperature and/or conditions appear to be a better indicator of stress and discomfort than many weather parameters. As a result of these research efforts, Dr. Mader was instrumental in developing a comprehensive environmental stress index that encompasses a range of temperatures from >120 degrees F to < -40 degrees F for domestic food animals (primarily cattle). The index adjusts ambient temperatures for relative humidity, wind speed, and solar radiation. The index is useful for tracking acclimation rate, stress level, and energy requirements as animals move from season to season and are exposed to adverse weather events. In addition, the model can aid in identifying emergency preparedness protocols, which might need to be considered when catastrophic environmental events occur.
Dr. Mader’s current activities include involvement in national and international projects studying and mitigating environmental effects on animal productivity. He is past-Chairman of the FASS Beef Cattle sub-committee on the Guide for Care of Agricultural Animals, past Chairman of the Professional Animal Auditors Certification Organization and has been an active member of the American Registry of Professional Animal Scientists. Previously, Dr. Mader was a recipient of the American Society of Animal Science Animal Management Award, an honorary professor of Animal Production at the University of Queensland in Australia, and OSU-Advanced Degree Graduate of Distinction Award. He is author or co-author of over 400 scientific publications. Dr. Mader has been Head of Mader Consulting, a business entity devoted to the implementation of ethical animal welfare and sustainable production practices as well as development of management strategies to minimize environmental stress and effects of climate variability on livestock.
2024 HONOREES

Duane H. Theuninck, Ph.D.
Dr. Duane Theuninck was raised on a family farm near Marshall, Minnesota. It was a typical Midwest farm where his family raised corn, soybeans, cattle and hogs, along with his mom’s flock of chickens. Duane’s interest in livestock production was nurtured as an active member of 4-H, where he showed cattle and pigs, participating with livestock judging teams and engaging in statewide 4-H leadership.
Duane received his Bachelors, Masters. and Ph.D. degrees in Animal Science from the University of Minnesota. His major professor, Dr. Dick Goodrich, was one of the inaugural inductees into the Legends of Feedlot Nutrition. It is very special and humbling for Duane to follow in those footsteps.
Dr. Theuninck began his career as a beef cattle nutritionist with Cargill’s feed business in 1981. His first role was research nutritionist at the research facility in Elk River, MN. The position also included technical service responsibility, and those early years provided opportunities to learn about all sectors of the beef industry across the U.S. From 1987 through 2002, Duane alternated between the research facility and Cargill’s offices in the Minneapolis area, where he provided technical leadership to Cargill Animal Nutrition’s beef cattle business around the world. Duane worked with colleagues in North and South America, Europe, Asia, and Africa. They worked on research, product development, and technical consulting for feedlot, stocker, and cow/calf operations.
One of the most challenging and gratifying aspects of Duane’s time with Cargill Animal Nutrition was working with a team to develop the Max system of ration formulation. It was amazing to be part of an extremely talented team that created parallel formulation systems for beef, dairy, and swine. BeefMax contains unique models of beef cattle nutrition that are used to feed millions of cattle around the world.
In 2002, Dr. Theuninck took on a new role as in-house nutritionist for Cargill Cattle Feeders (CCF). With five feedlots and a capacity of about 275,000 animals, CCF was one of the leading cattle feeding companies in the world. During his tenure at CCF, Duane developed a research facility, created a unique system for sorting cattle, and instituted new methods for mining the tremendous amounts of data generated by feedlots. While at CCF, Duane was active on the TCFA research committee and chaired the NCBA Beef Safety committee. He returned to Cargill Animal Nutrition in 2016, where he resumed technical leadership of the beef business until retiring in 2020.
Looking back at his 39-year career with Cargill, Dr. Theuninck will tell you that he was extremely fortunate to work with and learn from hundreds of excellent scientists and outstanding leaders. One of the most enjoyable and rewarding parts of the job was helping new employees grow and develop and become successful.
Duane and his wife, Deb Anderson, live in Canyon, Texas. Deb and Duane have four children that are scattered across four continents. They cherish time they get to spend with their children and one very special granddaughter.

Kendall Karr, Ph.D.
Dr. Kendall Karr grew up traveling to feedyards in Texas and Kansas with his feedlot nutritionist father, LOFN honoree, Dr. Mel Karr. The PNC now has its first father and son induction into the Legends of Feedlot Nutrition.
Dr. Karr not only loves the cattle industry, but he also loves the Equine industry. Kendall and Mel owned and trained running Quarter Horses with major wins in Texas, Oklahoma, and New Mexico. His racing career culminated in an invitation to the Champion of Champions race in California for the top ten horses in the country. In addition, while working on his M.S., he coached the Texas Tech Horse Judging team to a second-place finish at the World QH Congress and won the World QH show.
Kendall worked as an undergraduate research assistant at the Texas Tech Burnett Center for future feedlot nutritionists Dr. Johnny Horton, Dr. Bob Beville, and Dr. Dan Arnt, gaining further appreciation for the feeding industry that his father had instilled in him. He subsequently worked under LOFN inductee Dr. Rod Preston for his M.S. at Texas Tech University, where his research involved developing innovative grain processing methods. He went on to study for his Ph.D. at the University of Kentucky under the direction of Dr. George Mitchell and Dr. Karl Dawson, where his research focused on rumen microbiology. Following graduation from his Ph.D. program, Kendall joined the Purina Mills feedlot consulting team and moved to Lubbock to consult in the South Plains Feedyards. He was also actively involved in research at the Purina research facility and at his client’s feedlots.
In 1999, Kendall was hired by Cactus Feeders to join LOFN inductee Dr. Spencer Swingle as an in-house nutritionist. During his tenure at Cactus Feeders, he was promoted to Director of Nutrition Services and subsequently to Director of Research and Nutrition Services.
Kendall’s strengths as a consulting nutritionist lie in the training, mentoring, and development of feedyard personnel. His greatest satisfaction was watching many of these individuals succeed within the company. As an excellent teacher, he continually stressed the “why” and not just the “how” things are done. He is also proud of being instrumental in instituting the two-ration system of feeding to the Cactus organization, which is now used in all Cactus Feedyards and has proved to be economically beneficial.
As the Director of Research and Nutrition at Cactus, Kendall’s collaboration with Dr. Swingle and various trial sponsors led to many published abstracts and refereed journal articles. Dr. Karr has collaborated in research trials on numerous important industry topics, including:
- Tylan and roughage levels;
- Feeding value of new feed ingredients and additives;
- Supplementing different levels and sources of fat to low-fat WDGS;
- Possible liver abscess interventions;
- Serial harvest studies and implanting strategies in various production and feeding scenarios;
- Implanting long-day cattle after the FDA changes to reimplanting rules;
- Trials involving beef by dairy cross calves to determine how best to start, manage, and implant these cattle, including serial harvest studies to determine the optimum days on feed for the greatest return.
Kendall has been an invited speaker at many nutrition conferences including PNC, OSU, and ASAS, as well as international conferences in France, Mexico, and Argentina. He has also been affiliated with many industry organizations and advisory boards over his 32 years as a nutritionist, including: serving as a member of PNC since its inception and a past president; as chair and member of the TCFA research committee for over twenty years; and as a member of the industry and academia consortium that directed a USDA-funded research grant to determine the feeding value and supplementation of WDGS in the South Plains.
Dr. Karr and his wife Trish live in Canyon, Texas, near two of their daughters and four grandchildren. He looks forward to more grandchildren when his daughter, a veterinarian, gets married in June.