Increasing platform speed and the percentage of cows completing a second rotation improves throughput in rotary dairies

Abstract

This study sought to improve milking efficiency in rotary dairies by modelling the effect of increasing platform speed on the percentage of cows requiring multiple rotations to complete milking, i.e. ‘go-around’ cows, and cow throughput. Milking data, including 376 429 milking event records from 44 530 cows, were collected from 62 commercial farms with rotary dairies in New Zealand. Average rotation time, a function of platform speed and rotary size, was 10.0 ± 1.5 min, mean milking duration 383 ± 129 s, and mean milk yield 11.9 ± 3.8 kg per milking session. Milking duration data were normalised using a log10 transformation. An estimate of the percentage of ‘go-around’ cows and potential throughput over a range of platform speeds were made using the NORMDIST function of Microsoft Excel 2010. Results indicate that throughput continues to increase with increasing platform speed, despite a greater number of ‘go-around’ cows. If a potential shadow effect (whereby a ‘go-around’ cow may cause the following bail to be unoccupied) is considered, the optimum percentage of ‘go-around’ cows was ~20%. Accordingly, a change of operating practices in many rotary dairies is justified as the current target of 10% ‘go-around’ cows may limit throughput. In order to achieve greater cow throughput, platform speed should rather be set based on the capability of the operator attaching clusters. The difference between the current average rotation time and milking duration indicates that many dairies can increase platform speed and thus throughput. Furthermore, many work routines can be accelerated so faster platform speeds can be achieved without increasing labour requirements. The increased throughput potential of larger dairies is only realised when operated at fast platform speeds.