NAB is the first of the big four banks to crack down on poor treatment of animals by implementing animal welfare principles that will guide future lending decisions. 

A spokesperson for the bank says it understands the agricultural industry is a fundamental part of Australia's economy and maintaining its integrity was critical to its long-term sustainability.

"The new animal welfare principles reflect balanced input from a number of industry associations, animal welfare organisations, and other stakeholders," the spokesperson said.

The RSPCA says it welcomes the decision and hopes other banks will follow and incorporate animal welfare into their business and lending practices.