Customer Service Experts

Expertise to serve your needs

Cliff Ocker

Director of Sales and Client Relations

Growing up on a small dairy farm in south central Pennsylvania, Cliff Ocker’s roots in animal agriculture run deep. After earning his Associates degree in Agriculture Business Management from Penn State University in 1991, Ocker took on a dairy nutritionist role with a prominent feed company. Ocker spent 17 years in the field as a nutritionist with various feed companies, then translated his field experience to building and supporting customer relationships at a forage laboratory. Most recently, Ocker held a business manager position, selling a feed additive to improve fiber digestion.

Ocker joined Rock River Laboratory as the director of sales and client relations in 2018. In his current role, he forges relationships and shares expert insights, Read More from his vast experience, with customers and partners across the regional areas surrounding Rock River Laboratory’s five domestic labs in California, New York, Ohio, and Wisconsin. Outside of his customer support work, Ocker enjoys hunting, spending time with his two daughters and son, and coaching and playing softball and volleyball.

Cliff can be reached at: cliff_ocker@rockriverlab.com

Katie Raver

Animal Nutrition Technical Services Director

Born and raised in Eureka, Illinois, Katie Raver grew up enjoying rural and small-town living. Raver’s grandparents exposed her to their family farm - complete with sheep, horses, and crops. Running around that farm instilled a passion for agriculture at an early age. While pursuing a bachelor’s degree in animal science and ruminant nutrition, with a specialty in dairy at the University of Illinois, that passion grew through her work on the university dairy, participation on the Dairy Challenge team, and numerous dairy courses. Raver joined Rock River Laboratory as an intern in 2013, assisting in the launch of the FeedScan sample submission app.

After graduating, Raver’s desire to help producers and interest in nutrition drove her to pursue a Master’s degree focusing on forage quality, also at the University of Illinois. READ MORE She completed her second degree in 2015 and took on a dairy field technical specialist role while also gaining experience in both agronomy and beef nutrition. In 2020 Raver joined the Rock River Laboratory team again - this time as animal nutrition and field support specialist helping Southern and Western US-based nutritionists in advancing analysis opportunities for their dairy and beef operations as well as troubleshooting nutrition challenges. In 2025, she was promoted to her current role as technical services director, where she combines her vast experience and expertise to identify themes and trends that can fill in gaps for customers, analyze data to shed light on economically impactful opportunities, troubleshoot nutrition challenges, and offer insights into assessment and evaluation of forage quality. On weekends, you can find Raver outdoors horseback riding, hiking, and spending time on her hobby farm.

Katie can be reached at: katie_raver@rockriverlab.com

David Williams

Global Sales Director - Agronomy

Hailing from Cobden, Ill., David Williams grew up on a small family farm originally operated by his grandfather as a dairy. His passion for animal agriculture grew as his family raised commercial cattle, various poultry species, meat rabbits, horses, and pasture hogs.

After high school, Williams joined the United States Army as an infantryman, where his time included a combat deployment in support of Operation Iraqi Freedom. He later served with a mounted equestrian unit that performed ceremonial duties, cavalry tactics demonstrations, and training of deploying units on the use of pack saddles. He graduated from Oklahoma Horseshoeing School and served as the unit's farrier during his tenure.

Seven years of active duty behind him, Williams enrolled at Southern Illinois University, where he transitioned into an assistant manager at the university farm’s swine and beef units. Williams graduated with a Bachelor of Science degree in animal science in 2015 and earned a Master of Science degree in ruminant nutrition in 2016. With post-secondary complete, he managed Saline River Cattle Company, a Simmental-Angus seed stock operation, before joining Purina Animal Nutrition in 2017 where he carried account management and sales leadership roles in the Midwest.

Williams joined Rock River Laboratory in 2025 as the Global Sales Director. READ MORE In this role, he oversees, leads, and guides the agronomy sales teams spanning the lab network. Outside of his director role, Williams and his wife Charity, along with their children Lillian, Cora, Theo, and Phinehas, operate a small herd of Angus cattle on his family’s farm. David enjoys hunting, fishing, and the great outdoors. You may find him home-butchering, smoking, and dry-curing meat products, or experimenting with mead, cider, and wine production - in addition to time cooking. Williams’ strong passion for serving soldiers has also called him to pursue a commissioned officership as a Chaplain in the Illinois National Guard. He earned his Master of Divinity in 2024 through Liberty University and currently serves with the 106th Aviation Regiment based in Peoria, Ill.

David can be reached at: david_williams@rockriverlab.com

Aubree Hollowell

Animal Nutrition Client Support Specialist

Originally from Fort Cobb, Oklahoma, Aubree developed an early interest in animal agriculture and animal health through her experiences involving farming and cattle production. She earned a Bachelor of Science degree in Animal Science from Oklahoma State University and a Master of Science degree in Biology from Bemidji State University. Prior to joining Rock River Laboratory, Aubree held roles with Axiota Animal Health and RD LifeSciences, where she gained experience in animal health research, microbiology, biotechnology, and ruminant nutrition.

In her role at Rock River Laboratory, Aubree works closely with producers, nutritionists, and industry partners to help identify opportunities and solutions that support their operational goals. Outside of work, she enjoys traveling, attending live music events, spending time outdoors with family, friends, and her dog, and staying active through Pilates. An interesting fact about Aubree is that she has lived outside of the country in both St. Kitts and Grenada.

Aubree can be reached at: aubree_hollowell@rockriverlab.com

Joe Thelen

Regional Sales Representative, Agronomy

Native to Nebraska, Joe Thelen grew up in Randolph on a diversified farm that produced corn, soybeans, alfalfa, oats, dairy cows, beef cattle, and farrow-to-finish swine. This foundation fueled his early passion for advancing the agricultural industry and led him to pursue a degree in Agribusiness at the University of Nebraska–Lincoln, followed by roles with Waypoint Analytical, Ever.Ag, Proagrica, and Midwest Laboratories. Thelen joined Rock River Laboratory in 2026, where he is responsible for engaging with customers to identify solutions that help them make effective business decisions.

In his spare time, Joe enjoys spending time with family and friends, cheering on the ISU Cyclones and Nebraska Cornhuskers football and basketball teams, traveling, and participating in outdoor activities such as gardening, golfing, and landscaping.

Joe can be reached at: joe_thelen@rockriverlab.com