Feed cost efficiency in robotic milking systems: an analysis of revenue minus feed cost across dairy cow groups in southern Brazil.

This study aimed to evaluate the economic impact of grouping strategies on Revenue Minus Feed Cost (RMFC) in a guided-flow Automatic Milking System (AMS) in southern Brazil. RMFC was used as the main economic indicator and was calculated as the difference between milk income and feed cost per cow. This retrospective observational study was conducted on a commercial dairy farm using routine production and economic records from 76 Holstein cows managed according to the farm routine as a single group in 2022 and as high- and low-production groups in 2023. Daily milk yield, feed costs, and milk prices were recorded from February to August. Data were analyzed considering management group and month, using ANOVA and Tukey's test at the 5% significance level. RMFC was significantly affected by group type, feed costs, and milk price. The high-production group (LA) presented the highest feed efficiency (FE) and RMFC, despite requiring higher nutritional investment. The low-production group (LB) had reduced economic performance, especially in the final months of lactation. Under the evaluated farm conditions, the grouped strategy was associated with more targeted feeding management and with differences in technical and economic performance among groups. This study contributes to the economic evaluation of grouping strategies in AMS under commercial conditions, using RMFC and FE as technical-economic indicators.