Leadership Team

Nate Haas, DVM, MS, DACVM

President and Director of Research and Development

As the President of Bio-Vet, Inc., Dr. Haas is involved with all aspects of the company. He is instrumental in developing and overseeing research, communicating animal trial results, and providing expertise within the company to strengthen the Bio-Vet brand, product portfolio and programs. With his extensive knowledge of animal health, he is a key component in presenting technical data to our associated stakeholders. He supports the company with strategic and managerial leadership to help train company and distribution representatives and to assist in deployment of products within animal health programs.

Before joining Bio-Vet, Dr. Haas held positions in food animal veterinary practice, a Clinical Microbiology Residency at the Iowa State University Veterinary Diagnostic Laboratory, teaching positions at Madison College and University of Wisconsin-Madison School of Veterinary Medicine as well as serving as a veterinarian for the State of Wisconsin. He also held a district seat on the Wisconsin Veterinary Medical Association Executive Board of Directors and is board certified in the American College of Veterinary Microbiologists.

Dr. Haas resides in Wisconsin with his wife and 4 daughters.

He is a 2009 graduate of Iowa State University College of Veterinary Medicine.

Rebecca Wienkes


Becky Wienkes joined Bio-Vet in 2015. She has over 30 years of experience working with agriculture and agribusiness clients as a Certified Public Accountant.

Her leadership role at Bio-Vet focuses on leading a strong team, developing and implementing the company’s business plan, and ensuring the company’s financial stability.

Becky has been involved in agriculture her entire life-growing up on a 60-head dairy farm. She and her husband currently reside on and operate a beef and crop farm in Southwest Wisconsin.

Gary Grimsman

National Sales Director

Gary Grimsman is our National Sales Director and has been with the company since 1998. His previous positions included Senior Account Manager and Regional Representative.

As National Sales Director, Gary is involved with all aspects of the company, specializing in sales of Bio-Vet’s packaged goods and direct fed microbial products. He manages Bio-Vet’s sales force and coordinates new territory development.

A native of Carroll, Iowa, Gary has been involved in the animal health and nutrition business his entire life. He worked for a veterinary clinic and managed processing, nutrition consulting and vaccination work in major feedyards in western Iowa. Gary’s career experience includes the development and sale of his own line of oral drenches for dairy cattle.

Donald G. Faber

Bio-Vet Board of Directors & Special Assignment

Don Faber is an active member of the Bio-Vet Board of Directors. Don has over 35 years of experience in corporate strategic planning and fiscal overview, ranging from large corporations to governmental agencies and entrepreneurial start-ups. Don served eight years in the USAF Pararescue from 1967-1975. Don has a BS in Biology (1979) and an MBA with an emphasis in Finance (1989). His private sector highlights include six years as a planning analyst for Aramco (Saudi Arabia) and as a Co-founder of Midwestern BioAg in 1985 and a Co-founder, and still a shareholder, of Bio-Vet in 1996.

Don is currently on special assignment to the Bio-Vet Board of Directors to provide guidance on corporate growth and succession options.

William A. Zimmer, D.V.M.

Founder of Bio-Vet, Inc.

Dr. Bill Zimmer established Bio-Vet, Inc. in 1991, a company that has become synonymous with innovation in the creation and manufacture of animal microbial and nutrition products. He was involved with all aspects of the company. He specialized in the development of direct fed microbial products, incorporating DFM’s into farm programs, educating clients and animal producers on the proper use and expectations of probiotics and nutrition, and researching the effects of DFM’s on various animal production systems.

He graduated from the University of Wisconsin School of Veterinary Medicine in 1988.  Dr. Zimmer left a successful mixed animal practice in 1990 to concentrate on animal nutrition and natural systems of animal production. While his focus was on direct fed microbial systems for animals, he also had extensive knowledge of the interrelationship of animal health, nutrition, and soil biological and fertility systems.

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