It is estimated that 37 % of all food produced in Mexico for human consumption is lost or wasted, while the national dairy herd consumes approximately 455,000 tons of feed annually. This study proposes a method to carry out a national inventory of food losses (FL) from the agro-industry that can replace conventional feed in livestock diets. FL chosen should meet criteria such as documented evidence of its use as livestock feeds, knowledge of existing treatments to transform them into by-product feeds, information on its availability, nutritional composition data, and proximity to dairy farms. The method was applied in Mexico, considering national agricultural statistics data and livestock production statistics at the municipal level. FL estimation was made using the Commission for Environmental Cooperation method, considering the pre-harvest, post-harvest, and processing stages of the agri-food supply chain. The interaction between milk production and FL generation was calculated using the global desirability function and spatially assessed using geographic information systems. Twenty-nine potential "strategic food loss" were identified, including maize, carrots, broccoli, cotton, and potato. The highest opportunities to use FL as by-product feeds are in 52 municipalities, mainly in the West Central region, where the Bajio dairy area is located. This research is the first step toward developing a market for by-product feeds in a circular economy scheme that reduces the environmental impacts and costs in the dairy industry.