Cow milking order and its influence on milk production in a pasture-based automatic milking system

Context While several studies have documented the consistency of milking order and its association with milk yield in herds with conventional milking systems, there is limited data available on herds in the automatic milking systems (AMS) where cows move to the dairy voluntarily to be milked. Aims The present study was conducted to examine the consistency of milking order in AMS and its association with milk yield and cow characteristics. Methods The study was performed at The University of Melbourne Dookie Dairy in northern Victoria, Australia. The milking herd had up to 158 Holstein–Friesian cows in a pasture-based AMS with a three-way grazing system. The study utilised the individual-cow milking times, parity number, days in milk and data on daily production (milk yield in kilograms, fat and protein percentages and liveweight) from August 2017 till April 2018. Monthly milking order was determined for each milking session by ranking individual cows on the basis of their recorded time of milking. Key results A consistent milking order was observed with the order of cows at the beginning (percentile rank position 0–33) and end of the milking order (percentile rank position 68–100) being less variable than cows in the middle positions. Milking orders from any two consecutive months were highly correlated (P < 0.01). Energy-corrected milk yield was negatively associated with the milking position (5 of 9 months) and days in milk (8 of 9 months), but positively associated with parity number and liveweight (5 of 9 months). The cow factors such as energy-corrected milk yield, liveweight, parity and days in milk were poor predictors of milking order. This suggests that other factors such as health and social dominance might be of importance. Conclusions This observational study indicated that cows at the beginning of the milking order have a higher milk yield than do cows at the end of the milking order in pasture-based automatic milking systems. Implications Grazing-management strategies that allow cows at the end of the milking order to access fresh pasture are worthy of further investigation.