Craig Carr, Carrfields managing director, said the acquisition was a strategic opportunity for Carrfields Livestock to fill gaps in its current national network.
This acquisition will take the Carrfields Livestock team to over 150 livestock agents across the country.
Farm Source said it would help the small number of employees, who did not have the option to transition over to Carrfields Livestock, to find new opportunities within Fonterra.
Fonterra launched Farm Source in 2014 as a farmer-facing brand, providing service, support, rewards, digital technology, online shopping and financial options for farmers.
Farm Source livestock has about 25 agents across the country.