Automatic milking
Automatic milking
Automatic milking is the milking of dairy animals without human labour.
The milking process
The milking process is the collection of tasks specifically devoted to extracting milk from an animal (rather than the broader field of dairy animal husbandry). This process may be broken down into several sub-tasks: collecting animals before milking, routing animals into the parlour, inspection and cleaning of teats, attachment of milking equipment to teats, extraction of milk, removal of milking equipment, routing of animals out of the parlour.
Milking schedules
Maintaining milk yield during the lactation period (approximately 300 days) requires consistent milking intervals, usually twice daily and with maximum time spacing between milkings. In fact all activities must be scheduled around the milking process on the dairy farm. Such a milking routine imposes restrictions on time management and personal life of an individual farmer, as the farmer is committed to milking in the early morning and in the evening for seven days a week regardless of personal health, family responsibilities or social schedule. This time restriction is exacerbated for lone farmers and farm families if extra labour cannot easily or economically be obtained, and is a factor in the decline in small-scale dairy farming. Techniques such as once-a-day milking and voluntary milking (see below) have been investigated to reduce these time constraints.
Automation in milking
To alleviate the labour involved in milking, much of the milking process has been automated: many farmers use semi-automatic or automatic cow traffic control (powered gates, etc.), the milking machine has entirely automated milk extraction, and automatic cluster removal is available to remove milking equipment after milking. Automatic teat spraying systems are available, however there is some debate over the cleaning effectiveness of these.
The final manual labour tasks remaining in the milking process were cleaning and inspection of teats and attachment of milking equipment (milking cups) to teats. Automatic cleaning and attachment of milking cups is a complex task, requiring accurate detection of teat position and a dextrous mechanical manipulator. These tasks have been automated successfully in the voluntary milking system.
Voluntary Milking Systems (VMS)
Since the 1970s, much research effort has been expended in investigating methods to alleviate time management constraints in conventional dairy farming, culminating in the development of the automated voluntary milking system (VMS).
Voluntary milking allows the cow to decide its own milking time and interval, rather than being milked as part of a group at set milking times. VMS requires complete automation of the milking process, as the cow may elect to be milked at any time during a 24 hour period. A typical VMS layout is shown in Fig. 1. The milking unit comprises a milking machine, a teat position sensor, a robotic arm for automatic teat-cup application and removal and a gate system for controlling cow traffic. The cows are permanently housed in a barn, and spend most of their time resting or feeding in the loose-stall area.
When the cow elects to attend the milking unit (due to conditioned habit or udder fullness), a cow ID sensor reads an identification tag on the cow and passes the cow ID to the control system. If the cow has been milked too recently, the automatic gate system routes the cow past the unit. If the cow may be milked, the cow is routed into the milking unit, where automatic teat cleaning, milking cup application and milking takes place. As an incentive to attend the milking unit, concentrated feedstuffs may be fed to the cow in the milking unit, and the barn may be arranged such that access to the main feeding area can only be obtained by passing the milking unit.
The innovative core of the VMS system is the robotic manipulator in the milking unit. This robotic arm automates the tasks of teat cleaning and milking attachment and removes the final elements of manual labour from the milking process. Careful design of the robot arm and associated sensors and controls allows robust unsupervised performance, such that the farmer is only required to attend the cows for condition inspection and when a cow has not attended for milking.
Typical capacity for a VMS is 60-70 cows per milking unit. VMS usually achieve milking frequencies between 2 and 3 times per day, so a single milking unit handling 60 cows and milking each cow 3 times per day has a capacity of 7.5 cows/h. This low capacity is convenient for lower-cost design of the robot arm and associated control system, as a window of several minutes is available for each cow and high-speed operation is not required.
VMS units have been available commercially since the early 1990s, and have proved relatively successful in implementing the voluntary milking method. In fact VMS is the only automatic milking system (AMS) available to farmers. The terms AMS or “robotic milking” (RMS) are universally used to describe the VMS systems by the various manufacturers and the dairy industry press, however it can be seen that VMS is a specialised subset of AMS.
Advantages
Elimination of labour. The farmer is freed from the milking process and associated rigid schedule, and labour is devoted to supervision of animals, feeding, etc.
Increased milking frequency. Milking frequency may increase to three times per day, however typically 2.5 times per day is achieved. This may result in less stress on the udder and increased comfort for the cow, as on average less milk is stored. Higher frequency milking increases milk yield per cow, however much of this increase is water rather than solids.
Perceived lower stress environment. There is a perception that elective milking schedules reduce cow stress. An objective study found no decrease in stress between automatic and conventional milking.
Herd Management. The use of computer control allows greater scope for data collection. Such data allows the farmer to improve management through analysis of trends in the herd, for example response of milk production to changes in feedstuffs. Individial cow histories may also be examined, and alerts set to warn the farmer of unusual changes indicating illness or injury. Information gathering provides added value for AMS, however correct interpretation and use of such information is highly dependent on the skills of the user.
Disadvantages
High initial cost. VMS systems cost approximately €120,000 per milking unit (presuming barn space is already available for loose-stall housing). This does not compare favorably with conventional parlours, where a much higher milking capacity may be obtained for similar or lower cost.
Low return on investment. The low capacity of VMS systems means that economy of scale cannot be used to offset the high capital investment. A VMS takes longer to pay for itself than a conventional parlour.
Increased complexity. While complexity of equipment is a necessary part of technological advancement, the increased complexity of the VMS milking unit over conventional systems reduces the ability of the farmer to perform repairs, increasing reliance on manufacturer maintenance services and possibly increasing operating costs. The farmer is exposed in the event of total system failure, relying on prompt response from the service provider. If service is not immediately available the farmer must milk the herd with a single milking unit or use a redundant backup parlour. In practice VMS systems have proved robust and manufacturers provide good service networks, but the risk remains present.
Difficult to apply in pasture systems. VM works best in zero-grazing systems, in which the cow is housed indoors for most of the lactation period. Zero-grazing suits areas (e.g. the Netherlands) where land is at a premium, as maximum land can be devoted to feed production which is then collected by the farmer and brought to the animals in the barn. In pasture systems, as used in most of the world, cows graze in fields and are required to walk to the milking parlour. It has been found that cows tend not to attend the milking unit if the distance to walk is too great.
Lower milk quality. Somatic cell count (SCC)and Plate loop count (PLC) are, respectively, measurements of the quantity of white blood cells and total number of bacteria present in a milk sample. A high SCC indicates reduced udder health (as the immune system fights some infection) and implies lower milk quality. Machine milking of any kind increases SCC, however VMS herds consistently show higher SCCs than conventionally milked herds. A high PLC indicates bacterial contamination, usually through poor sanitation or cooling and similarly implies low milk quality. High PLC in VMS may be attributed to the continuous use of milking lines (rather than twice a day in conventional systems), which reduces the time window for cleaning, and the incremental addition of milk to the bulk milk tank which may not cool efficiently at low milk levels.
Possible increase in stress for some cows. Cows are social animals, and it has been found that due to dominance of some cows, others will be forced to milk only at night. Such behaviour is inconsistent with the perception that VM reduces stress by allowing "free choice" of milking time.
Decreased contact between farmer and herd. Effective animal husbandry requires that the farmer be fully aware of herd condition. In conventional milking, the cows are observed before milking equipment is attached, and ill or injured cows can be earmarked for attention. Automatic milking removes the farmer from such close contact with the animal, with the possibility that illness may go unnoticed for longer periods and both milk quality and cow welfare suffer. In practice, milk quality sensors at the milking unit attempt to detect changes in milk due to infection, and farmers inspect the herd frequently. However this concern has meant that farmers are still tied to a seven-day schedule.
Environmental concerns. Cows at pasture spread waste (manure) on the pasture. Concentration of animals in zero-grazing VM systems increases the accumulation of excrement that must be collected and treated by the farm.
Current AMS manufacturers
SAC. (Denmark) Purchased the Dutch manufacturer of the Galaxy Robot AMS in 2005. [1]
PUNCH Technix. (Netherlands) Titan AMS [2] (May incorporate former Prolion, AMS Liberty and Gascoigne Melotte AMS)
DeLaval. (Sweden) DeLaval VMS [3]
Lely. (Netherlands) Lely Astronaut AMS [4]
Fullwood. (UK) Merlin AMS (Rebranded Lely system) [5]
References
Rossing, W. and Hogewerf, P. H., (1997), “State of the art of automatic milking systems”, Computers and electronics in agriculture, Vol. 17, pp. 1-17
Hogeveen, H.,W., et. al., (2001), “Milking interval, milk production and milk flow-rate in an automatic milking system”, Livestock Production Science, Vol. 72, pp. 157–167.
EU project Automatic Milking [6]
Schukken, Y.H, Hogeveen H., and Smink, B.J., (1999), "Robotic Milking and Milk Quality, Experiences From the Netherlands", National Mastitis Council Regional Meeting Proceedings 1999, pp 64 - 69 [7]