The business opened its Bendigo site in Harpin Street to the public on Friday giving friends and family of staff, as well as professionals including vets, a chance to tour the facility.

Site manager Neil Sammons said 84 people work at the Bendigo site which is a hive of activity.

"We manufacture about one third of the products the business in Australia sells," he said.

"Today is a chance to have a walk around, see what we do, see how we run the business and see where some of your relatives and friends work.

"We make vaccines but the company markets a full range of animal health products.

"But, specifically here in Bendigo, we make vaccines."

Mr Sammons spoke to tour participants about the site's history and various ownership changes over the years.

"Here on this site we manufacture vaccines and we've been doing that for nearly 28 years," he said.

"The company started as a small company called Ausvac and we started making vaccines for pigs in a small building further down the block. I was working for the company at the time ... we grew over the next 10 years and developed more and more pig vaccines and we started developing some cattle vaccines until 1998 when Intervet took over. They were already a big international company and they really put some money into this site.

"They spent $30 million over the next five years developing this site and expanding the range of vaccines that we manufacture here."

Mr Sammons said dog and cat vaccines became very important to the business.

"The dog and cat vaccines almost represent half of the business that we do out of this facility," he said.

The company changed hands again in 2007 and is now affiliated with the Coopers Animal Health brand.