Milking robots

Automatic milking is an established reality in dairies around the world. The advantages are many, from the almost total reduction of manual work to the possibility of collecting data on individual animals, for more efficient herd management. On the other hand, it must be remembered that the milking robot is a machine that requires specific skills

Milking automation was undoubtedly a revolutionary change in dairy farming. The change from conventional to automatic milking has brought about major changes for the farmer and the animals, introducing a new concept of herd management. Some operations are no longer necessary, others have been modified and adapted to the new milking system and activities have been introduced that did not exist before.

Some of the most important aspects related to the introduction of the milking robot (AMS, Automatic Milking System) are undoubtedly the change in the nature of work, with the conceptual component overriding the manual one, and the possibility of monitoring the animals on an individual basis through electronic devices. This is because the daily monitoring of the status of the cows is no longer carried out by the milker, but is delegated to a series of sensors installed on the AMS, so that the consultation and analysis of the resulting data requires the use of management software and, not least, time. In fact, although there is a drastic reduction in manual work, management activity must still be taken into account. The computer therefore becomes a fundamental tool for the farmer, helping him to better support the decision-making process in the barn.

The first milking robot was installed in 1992 in the Netherlands. After 30 years, the technical evolution has allowed these machines to reach a very high reliability and efficiency, thus promoting their commercial spread. It is estimated that there are about 50,000 milking robots operating in the world, of which over 1,200 in Italy (i.e. 4-5% of farms).

From a technological point of view, the AMS is a complex system, made up of several parts including the milking box, the electronic identification system and the teat tracking system, the robotic arm and a series of sensors, with associated data management software.

These structures must be closely interconnected and have a high degree of modularity in order to best meet both the physiological needs of the animals, which differ in morphology and behaviour, and the extremely diverse farm situations in which the AMS are installed.

 

The milking box

This is an automated stall, with the main function of restraining the cow during the milking phase. The solutions offered on the market vary depending on the manufacturer and the model of AMS, and concern single or multiple stall solutions.

The former are characterised by an independent stall, equipped with a robotic arm that carries out all milking phases on one animal at a time. In multiple stall systems the AMS is equipped with a mobile arm that can move from one stall to another; in this case, each stall is equipped with independent teat cups, allowing the robot to handle several animals at the same time.

An automatic livestock feeding system is usually contained in the stall, allowing the feeding of concentrated feed, in order to encourage cows to visit the milking stall even when the need to be milked is low, thus increasing the number of visits and milking frequency.

 

The electronic identification system

This is a key element of the robotic milking routine. Recognition of the animal in the milking stall is normally carried out by means of an RFID (Radio Frequency Identification) transponder inserted into an anklet attached to a hind leg, or into the collar. Once the cow has been recognised and it has been verified that it is actually her turn, the AMS activates milking, feeding and monitoring operations, updating the management software with all the animal's production and physiological data.

 

The nipple tracking system

It is without doubt the most sophisticated element of the whole AMS. The position of the teats varies not only from one animal to another, but also between successive milkings of the same cow. This requires real-time localisation of the nipples, whose accuracy must be such that the sheath can be applied to the nipple with a high success rate. Today, 3D cameras, ultrasound sensors and laser localisation devices are used. To detect any movement of the animal during the device attachment, some AMS implement tactile sensors in direct contact with one or more parts of the animal.

All of the technologies listed offer positive results for nipple localisation, with a success rate of more than 95%; the adoption of one technology over another stems from purely commercial philosophies.

This is followed by pre-milking cleaning to remove dirt and debris from the teat (preventing contamination of the milk) and to induce the milk ejection reflex, which is essential for proper milking.

The most common cleaning systems are based on the use of dedicated teat cups or counter-rotating brushes. In the first case, water and air are injected into the sheath, generating turbulence to clean the entire surface of the teat, after which the teat is dried with a jet of air. In the second case, a pair of counter-rotating brushes attached directly to the automatic arm of the robot cleans each individual teat. In both cases, the devices are disinfected at the end of the operation to prevent any cross-contamination between cows. Because it is timed, automatic cleaning may be less thorough than when an experienced milker intervenes, so it is imperative to keep cows as clean as possible from the time they are housed in the cowshed.

 

The robotic arm

The cluster or individual teat cups are attached to the cow by a robotic arm, also called an end-effector, which is available in two different types: The milking cluster is located at the end of the end-effector and the teat cups are applied to the cow in close succession; The end-effector picks up the teat cups one by one from a special storage rack and applies them individually to the cow's udder. The movements of the robotic arm must be fast, precise and silent; they are therefore performed by electric motors and/or pneumatic or hydraulic actuators. In the case of hydraulic actuators, the AMS is equipped with a hydraulic pump integrated in the unit, while in the case of pneumatically-actuated actuators, an external air compressor (usually spiral) is used.

At the end of milking and before the next cow comes in, the liners are washed with hot water, and in some cases sanitised by blowing pressurised steam at over 120°.

 

Sensors and management software

Numerous sensors are implemented in the milking robots to measure and analyse production, milk quality and the health status of the cow. With regard to production, in addition to the quantity produced per cow, it is also possible to measure the flow of milk per quarter, as well as the frequency of visits that the cow makes to the robot, with the related duration. With regard to quality, sensors are installed to record the fat, protein and lactose content of the milk. From a health point of view, there may be a device that counts somatic cells (the so-called "cell counter"), by means of optical or viscosity measurements of the milked milk. This sensor is useful for rapidly assessing the possible presence of clinical and sub-clinical mastitis per breast quarter. The presence of blood in the milk, which is an indicator of both an inflammatory state of the udder and trauma to the animal, can be detected by a colorimetric sensor. Progesterone dosage from a small volume of milk taken during milking can show the presence of heat and/or pregnancy in the cow. The presence of an electronic scale, capable of separately measuring the load on the cow's four limbs, allows daily monitoring of body weight variations and early detection of foot lesions. From the short list above, it is clear that the robot is able to collect a large amount of data. This data is then recorded, processed and archived by special management software, equipped with increasingly intuitive interfaces capable of providing the farmer with both detailed information on the individual animal and summary reports. In this way, the farmer can have an advanced information system, which, suitably adapted to the characteristics of the herd, allows attention to be focused on any critical points, providing useful support for management choices in the barn.