Ergonomic Fitting of Hock Rail Height in Milking Parlours

Many dairy farmers suffer from musculoskeletal ailments, such as upper extremity– associated disorders. Further, they have problems with their knees. As the number of animals in dairy farms has increased, so has the workload. This may lead to a strenuous amount of work especially during milking. Ergonomics affect every person, yet the aim of improving posture in the work environment is often neglected. The change of husbandry systems from tethered housing to loose housing has shifted the milking procedure from sitting milking to standing milking in parlours. Although this shift has been associated with improved posture, health problems in dairy farmers could not be alleviated. The present study aimed at quantifying the workload during the attachment task, which presented the most strenuous task during milking. The study was carried out on 15 different farms (three farms of each parlour type: autotandem, herringbone 30°, herringbone 50°, parallel, and rotary) with two subjects per farm during one full shift of milking. The posture of milkers was analysed by the CUELA (ComputerAssisted Recording and Long Time Analysis) system. CUELA recorded positions of joints and body regions according to the neutral zero method. The 25 th , 50 th , and 75 th percentiles described the distribution of angular degrees for each joint. The postures were evaluated according to international standards, which rated the angular degrees of joints as acceptable, conditionally acceptable, or not acceptable. A generalised linear mixed-effects model was used to evaluate the data by accounting for the hierarchical experimental design. The results showed that the interaction between hock rail coefficient (hock rail height divided by milker height in cm) and parlour type had a significant effect on ergonomics. Hence, the ideal hock rail height varied between the different parlour types. Whilst the milkers’ ergonomics in the parallel and herringbone 30° parlours benefited from a lower hock rail height, the ideal hock rail heights in autotandem or rotary parlours were higher. No hock rail height at which more than 69% of all joints were in an ergonomically acceptable range could be found in the 25 th , 50 th , and 75 th percentiles. In this work, we developed a hock rail height formula. This formula enabled us to calculate hock rail heights specific to the parlour type and milker’s height and to offer recommendations on the ergonomic fitting of hock rail heights in a variety of milking parlour types.