Agricultural Intelligence Measures Act of 2021 or the AIM Act of 2021 This bill establishes the Office of Intelligence in the Department of Agriculture (USDA) under the National Intelligence Program. The office must leverage the capabilities of the intelligence community and the intelligence-related research of the National Laboratories to ensure that USDA is fully informed of threats by foreign actors to U.S. agriculture; focus on understanding foreign efforts to steal U.S. agriculture knowledge and technology, and develop or implement biological warfare attacks, cyber or clandestine operations, or other means of sabotaging and disrupting U.S. agriculture; prepare, conduct, and facilitate intelligence briefings for USDA; operate as the liaison between USDA and the intelligence community, with the authority to request intelligence collection and analysis on matters related to U.S. agriculture; collaborate with the intelligence community to downgrade intelligence assessments for broader dissemination within USDA; and facilitate the sharing of information on foreign activities related to agriculture with the intelligence community.