Livestock feed production for the intensive dairy industry has a significant environmental impact. This study evaluated the potential to reduce the environmental impacts of milk production in Guanajuato, Mexico, by incorporating broccoli stems (BS), an abundant agro-industrial waste product with high nutritional value, into dairy cattle feed. The potential reduction of environmental impacts from adding BS to cattle diet formulation was estimated using a life cycle assessment and a linear programming model which considered nutritional requirements as constraints. Two scenarios for milk production were considered: an optimized conventional diet and an optimized diet including BS. The results indicated that incorporating BS in cattle feed could reduce greenhouse gas emissions by 118 g CO2 eq kg−1 fat-and-protein corrected milk (FPCM and agricultural land occupation by 0.002 m2a kg−1 FPCM but increased fossil depletion by 4 g oil eq kg−1 FPCM. BS can replace 11.1% of conventional feeds and maximize the incorporation feeds with low environmental impacts in the diet, such as alfalfa hay and maize silage. A sensitivity analysis of the economic allocation showed that the maximum price of BS to remain environmentally viable was 19.28 USD t−1 on a fresh matter basis