A systematic mapping of empirical studies of milking and operator efficiency in dairy farming

The current challenges associated with increasing global demand for dairy products, developing herd structures, and declining availability of labor have resulted in the need for improvements in contemporary dairy farm infrastructure and management practices. Internationally, across different production systems, the milking process accounts for between 33% and 75% of annual labor requirements on commercial dairy farms. Because milking efficiency is multifactorial and highly context-specific, a clearer understanding of the factors that influence it-as evaluated through key performance indicators-is required to support future optimization strategies. This study conducted a systematic review of the milking efficiency literature to identify knowledge gaps and evaluate how previous research approached this topic. Five research questions (RQ) guided the review, relating to contributions by country and production system (RQ1), problem types and research objectives (RQ2), methodologies used (RQ3), milking efficiency values across parlor systems (RQ4), and the effect of operator involvement (RQ5). Fifteen publications were analyzed, representing 23 sample groups and 315 parlors. Outcome variables included cows milked per hour (cows/h), cows milked per operator per hour (cows/h per operator), cows milked per cluster per hour (cows/h per cluster), and clusters per operator (clusters/operator). Four parlor types were represented: herringbone double-up, parallel double-up (P-DU), herringbone swing-over (H-SO), and rotary (RO). The United States and confinement-based systems contributed the most studies. Comparative research was the dominant problem type, and time-and-motion analysis was the most frequently used methodology. The P-DU parlors achieved the greatest overall throughput (352 cows/h), RO parlors achieved the highest operator-level efficiency (143 cows/h per operator) and clusters handled per operator (27 clusters/operator), and H-SO parlors achieved the highest throughput per cluster (5.6 cows/h per cluster). Across all parlor types, increasing operator number did not significantly increase hourly cow throughput or cows/h per cluster, but significantly reduced cows/h per operator and clusters/operator at milking. This systematic review synthesizes the structure, methods, and empirical findings of the milking efficiency literature. It provides a summary understanding of milking efficiency levels across a range of parlor types operating in different production systems and quantifies the effect of operator on milking efficiency levels relative to parlor type. For researchers in this field, the authors of this review have highlighted key directions for future investigation into milking efficiency optimization through the alignment of parlor infrastructure, automation specification, and management practices at milking.