Open access peer-reviewed chapter
Abstract
Control of diseases in dairy farms is based on various management factors, such as separation of dairy farms from other domestic and wild animal species, control of human circulation and contact with cows, cleaning and disinfection of vehicles, equipment, surfaces, and other unanimated secondary sources of contamination, feed and water hygiene, waste management, and management of technological processes (e.g., calving management, colostrum management, and milking management). In dairy farms, the milking parlour surfaces should be cleaned regularly and disinfected twice daily to avoid the multiplication of pathogens. Some biosecurity measures that can prevent the spreading of mastitis in dairy farms are the use of personal protective equipment (e.g., milkers’ gloves and milker overall), treatment of all infected quarters at the end of lactation (blanket dry cow treatment), removal of udder hair (shaving or singeing), and washing unclean udders. This chapter details biosecurity and hygiene solutions in the cattle milking parlour.
Keywords
- biosecurity
- risk management
- health management
- milking hygiene
- dairy farming
1. Introduction
Despite the continuous involvement of governmental and non-governmental institutions in developing and promoting milk quality standards and good milk handling practices in dairy farms, the negative attitudes and low knowledge of some processors and dairy farmers are still affecting the prevention and control of zoonoses and antibiotic residues, with a real impact on public health [1, 2].
In dairy farms, control of diseases is based on various management factors, such as separation of own cows from other domestic and wild animal species, control of human circulation and contact with cows, cleaning and disinfection of vehicles, equipment, surfaces and other unanimated secondary sources of contamination, feed and water hygiene, waste management, and management of technological processes (e.g., calving management, colostrum management, and milking management) [3].
Consumers must have access to clean and safe dairy products, and all supply chain actors must accept and apply good milk practices, regulations and standards [2]. The main biosecurity measures that can prevent the spreading of mastitis in dairy farms are the use of personal protective equipment (e.g., milkers’ gloves and milker overall), treatment of all infected quarters at the end of lactation (e.g., blanket dry cow treatment), removal of udder hair (shaving or singeing), and washing dirty udders. However, the safety of milking and raw milk is influenced by a group of management and control measures applied throughout the entire farm, designed to reduce the microbial load in the environment and raw milk (e.g., dairy herd health control, good milking practices, and milking parlour hygiene control) [4].
2. Milking biosecurity in cattle dairy farms
Milking biosecurity measures should take into account all sources of germs that might infect the udder and contaminate the milk, beginning with the environment and the cows being milked, then milkers and milking equipment, and finally milking and water [4, 5].
2.1 Milking environment
The production of good-quality milk is mainly influenced by the sanitary condition of the milking area [6]. Maintaining the good sanitary condition of barns and parlours is an important task of internal biosecurity on dairy farms. Also, clean and dry bedding is important to reduce the growth and transfer of microorganisms to the exterior of the teats and from here to the teat canal and milk [6, 7]. Therefore, identifying the practices that expose the teat end to wet and muddy pens, faeces, and dung and favour the growth and transfer of microorganisms will decrease the risk of occurrence of mastitis and milk contamination.
2.2 Cows
Cows are a major source of microorganisms that can infect the udder and contaminate the milk. All cows with mastitis must be identified before the spreading of microorganisms to other cows, and indicators of udder infection should be used in all dairy farms. Somatic cell count (SCC), which comprises leucocytes (75%), such as neutrophils, macrophages, lymphocytes, and erythrocytes, as well as epithelial cells (25%), is a good indicator of udder infection. When there is a bacterial infection, tissue damage, or stress, leucocytes grow and defend the body of the cow and combat pathogens. The quality of raw milk is negatively impacted by increased SCC in milk. However, low milk supply, changes to milk consistency, a decreased chance of appropriate milk processing, a lack of protein, and a significant risk for milk hygiene since it may potentially include pathogenic organisms are all characteristics of subclinical mastitis [8].
Even when the mammary gland is free of culturable pathogens, milk contains its own resident microbial community, the vast majority of which are not related to mastitis [9]. Falentin et al. discovered that 76 milk samples from healthy quarters included a high number of the
As a result of the research on raw milk microbial ecology, −omics methods are currently being applied to the sensu stricto milk microbiota of dairy ruminants. As a result, its effects on the physiology and health of the breastfeeding mother and her suckling progeny are becoming increasingly clear [13]. The discovery of a milk microbiome linked to desired production qualities such as high milk output and low SCC, as well as protection against infectious mammary infections, would be critical in reducing antibiotic use on dairy farms [14]. Furthermore, there is a rich array of bacteria in bovine milk that play critical roles in promoting gastrointestinal tract development and aiding immune function maturation in offspring [15]. Because the bovine milk microbiome promotes early-life gut development by boosting intestinal microbiota and immunological functions, removing this microbiota may do more harm than good in cow herd health management. Drinking water, milking equipment, bedding, skin, faeces, and the barn environment are all external microbial sources of bovine milk microorganisms [9, 15, 16]. Endogenous transfer routes include entero-mammary, rumen-mammary, and mammary resident microorganisms [15, 17, 18]. Therefore, the application of -omics sciences to the milk microbiota is anticipated to increase our understanding of open questions and challenges, including the aetiology and dynamics of sub-clinical and culture-negative mastitis, the effects of farming management choices on the health of the mammary gland and the offspring, the function of the intestine as a mastitis pathogen reservoir, and the dynamics of drooling in dairy ruminant farms [13].
A milking biosecurity plan must include the udder cleaning before milking (to increase the quality of cleaning, the udders of the lactating cows should be clipped). In the evaluation of milking biosecurity, it is important to know how the teats are cleaned before milking. The following ways of cleaning were described: pre-foaming, dry cleaning with separate towels, wet cleaning and drying afterward with separate towels, and wet cleaning but not drying afterward. Also, it is important to know if the foremilk is examined during fore-stripping if the teats are disinfected after the teat cups are removed, and if cows are kept upright for a period after milking. To prevent the spreading of mastitis, cows must be milked in a specific order: it is recommended that the cows with mastitis and/or a high SCC be milked last. Also, mastitis prevention can be done by culling chronically infected cows.
Periodical hygiene and udder health evaluations should be considered on dairy farms. To prevent the spreading of udder pathogenic bacteria (e.g.,
The studies of Zigo et al. revealed that the interplay of effects between methods of prevention that offer protection against the emergence of new infections and disease control methods, which significantly shorten the duration of the infection, leads to unique and continuous progress in the reduction of mastitis by the implementation of a mastitis control program. The incidence of clinical mastitis in the herd can be reduced to a minimum via constant observation of the hygiene practices in milking, treatment of dairy cows with efficient treatments for cows with clinical mastitis, and disposal of cows with the chronic form [24].
2.3 Milking personnel
The health experts involved with the dairy herd may not always be able to explain why preventive or treatment programs based on established risk factors for mastitis fail and the milk cow becomes infected [25]. Also, during milking, cooling, storage, and processing, sterile milk from the udder of a healthy cow becomes infected. A possible explanation is that not only cows, equipment, and milking routines are involved in milk contamination, and herd health plans designed for better milk quality must consider milking personnel as one of the factors [26]. Pathogens can be introduced directly into milk by milk-handling workers (milkers), especially if they are careless, ignorant, or deliberately negligent, Farm workers should be in good health and understand the value of hygiene because organisms can be present on the milker’s hands, nasal cavities, mouth, skin, and gastrointestinal tract [4].
2.4 Milking equipment
In the management of dairy herd, milking is a fundamental component that can affect both dairy herd health and milk production [27]. Milking systems can be classified into conventional milking systems (CMS) and automatic milking systems (AMS). The type of milking system installed on a dairy farm is determined by several factors, such as the number of cows, the cost and quality of manual labour, the level of milk production, and the availability of spares and services.
In small dairy farms, the recommended CMS are trolley systems (one or two milking groups are housed on the trolley, transported inside the barn, and managed by one operator) and the bucket milking system (BMS). In BMS, one operator can control up to three milking buckets connected to the vacuum pipeline. A disadvantage of trolley systems and BMS is that the operator must transfer the milk from the buckets to the transport bulk tank and move it out of the stable. However, trolley systems and BMS are very useful for milking a fresh cow, a sick cow, or a cow separated for treatment. Among the advantages offered by BMS on a traditional small dairy farm are: obtaining clean, completely untouched, high-quality milk, increased farm profitability and productivity, reducing dependence on labour, the possibility of developing the farm, and increasing the size of the herd [28].
The biosecurity risk associated with milking in small dairy farms should be considered in the following tasks of the routine of trolley and bucket systems: (a) bucket or trolley positioning; (b) pre-dipping; (c) foremilk inspection; (d) pre-milking udder preparation; (e) teat cups attaching; (f) removing of the teat cups; (g) post-dipping; (h) emptying of bucket or container; and (i) relocation of trolley. For each task, the risks associated with udder infection (dairy herd health) and/or milk contamination (public health) must be considered in the farm’s biosecurity plan.
On small and medium dairy farms, the recommended CMS are milk lines (two fixed pipes for milk and vacuum connected at a milk room and a machine room, located near the barn). The milk line system can be used with or without automatic cluster removal [28, 29]. The biosecurity risk associated with the milk line system should be considered in the following tasks: (a) milking group positioning; (b) pre-dipping; (c) foremilk inspection; (d) pre-milking udder preparation; (e) teat cups attaching; (f) teat cups removing; (g) post-dipping; and (h) group removal. As in the case of trolley and bucket systems, in farms with the milk line system, the biosecurity plan must consider the risk of infectious agents spreading during milking by analysing each task.
On large dairy farms, the recommended CMS are milk lines, parlours and AMS. The biosecurity risk on dairy farms with parlours should consider the following tasks of routine milking: (a) cow entry; (b) pre-dipping; (c) foremilk inspection; (d) pre-milking udder preparation; (e) teat cups attaching; (f) post-dipping; and (g) cow exit. Common types of milking systems used in dairy parlours are parallel, tandem, rotary, and robotic. Both CMS and AMS have benefits and disadvantages for milking biosecurity, and the conversion from conventional to automatic systems is not always accepted by farmers. The main benefits of AMS on a dairy farm are reduced labour (with the consequent reduction of the risk of introducing and disseminating pathogens through farm workers), a better social life for farmers, and improved milk yields due to more frequent milking [30]. Neijenhuis et al. showed that, in farms with automatic milking, the risk factors for mastitis are more or less comparable with those found in conventional milking [31]. However, the main physical performance indicators of CMS and AMS (e.g., milk production per cow, milk production per hectare, pasture grazed per hectare, or milk solids per full-time equivalent) are similar [32]. Unfortunately, high-technologized milking parlours come with some disadvantages, like periodic planned services and regular maintenance, changing of milking liners, and other milking system parts. In large dairy farms, inefficient or incomplete milking, poor milk quality, teat trauma, and mastitis infections are frequently associated with poorly serviced, maintained, and operated milking equipment.
In developing countries, the source of many microorganisms can be poorly cleaned and sanitised milking utensils [33], but this risk remains on all dairy farms where biosecurity measures are not respected or when malfunctions or accidents associated with milking equipment are not identified and reported immediately. Because milk is an excellent medium for the growth of a variety of bacteria, equipment and utensil surfaces with milk residues will facilitate the growth of numerous microorganisms, including pathogens [34]. Therefore, milking equipment should be made with easy-to-clean materials (e.g., stainless steel) and maintained in good condition (regular revisions) [4].
Milking equipment cleaning and sanitation are a mix of chemical, thermal, and physical procedures that require a short reaction time to be successful [25]. Pre-rinse, washing phase, and post-rinse are the three primary phases of an automated cleaning procedure. The pre-rinse phase is critical for removing the majority of milk remains. Alkaline or acid detergents should be used during the washing phase. Alkaline detergent aids in the removal of organic residues like milk protein and fat. Mineral deposits in water and milk are removed regularly using acid detergent [35, 36]. There are several milking machine cleaning solutions on the market, both caustics and acids, although sodium hypochlorite and sodium hydroxide are the most popular active components of caustic detergents, while phosphoric acid is the most popular acidic product. However, because milking machine distributors frequently stipulate which sanitizers are permitted, the usage of milking machine detergents is heavily impacted by the milking equipment [36].
2.5 Milking
In milking biosecurity, a good milking routine is very essential. In certain underdeveloped nations, most farmers do not wash their cows’ udders before milking, therefore, milking practices should be modified to promote better sanitary conditions [37]. However, udder cleaning before milking should be viewed as a method of removing mud but not of removing germs from the cow’s skin.
The milking routines used in European dairy farms with milking parlours should guarantee that the product obtained is of the greatest possible quality (e.g., hygienic removal of milk from the udder and prevention of mastitis), the work practices used are safe (e.g., milking operators should have a best practice milking course and use safe cow handling practices), and the time spent milking cows is used efficiently (e.g., milking row times of less than 9 minutes). An efficient milking routine has the following components: (1) parlour preparation, (2) row filling, (3) milking preparation, (4) batch preparation and milk let-down maximisation, (5) cluster attachment, (6) cluster removal, (7), teat disinfection, (8) row exit, and (9) parlour hose down [38].
The waiting time in the collecting yard before milking should be kept to a minimum in order to prevent cows from becoming anxious and dirty before being milked and to minimise the risk of foot injuries (e.g., solar ulcers). Parlour preparation should consider rinsing the collecting yard floor and walls, checking the availability of teat dip, and ensuring that the milking plant has been washed and is ready for milking. To avoid overstressing cattle during row filling, allow the cows to join the row without leaving the pit.
Farmers use a variety of methods for pre-milking udder preparation. A proper pre-milking cleanliness regimen can lower the cow infection ratio by lowering not just udder bacterial contamination from the environment, but also bacterial contamination from other diseased cows [39]. Disposable nitrile gloves (rinsed and disinfected routinely during the milking) and a clean parlour suit should be used to avoid the spread of mastitis and to keep the operator clean and free of discharges. Teats should also be washed (e.g., with a dry wipe), dried (e.g., with a paper towel), and fore milked 90 seconds before the cluster attaches (it aids in the early detection of mastitis and guarantees that optimal milk let-down occurs when the cluster is connected shortly thereafter) [38]. All pre-milking procedures, including wet washing and manual drying with paper towels, will result in the lowest bacterial levels [40, 41]. Udder dryness at the time of machine attachment is a critical part of pre-milking udder care [40]. Allowing a gap of about 90 seconds between batch preparation and cluster attachment enhances milking efficiency and maximises milk let-down. Preparing each cow reduces the amount of time spent walking up and down the parlour [38].
Many farmers now dip teats pre-milking with different disinfection solutions such as iodophor solution, iodine-based gel, sodium hypochlorite, dodecylbenzene sulfonic acid (DDBSA), chlorine, chlorhexidine, phenolics, and alcohol instead of washing and drying them [41, 42, 43, 44, 45]. Therefore, preventing mastitis begins with reducing the bacteria count in the teats before milking. Before cluster attachment, for efficient oxytocin release and milk ejection, 15 seconds of pre-stimulation followed by a brief latency interval should be performed [46]. The cluster attachment should be with the hand closest to the cow’s exit side (typically the closest to the cow), keeping the pulse and milk tubes on the exit side of the cow and out of the way when going to the next group. In this way, handling time is reduced and the risk of contamination of the cluster is reduced. Manual cluster removal should be done with the hand that the milker intends to attach to the next cow. If cluster attachment and removal are automated, then removing the clusters should be done at the proper flow rate. Allowing the unit to become limp on the udder reduces the danger of an air blast happening after cluster removal, lowering the risk of mastitis and teat-end injury [38].
Post-milking teat disinfection aimed at getting total coverage of the teat will destroy the most germs and utilise an emollient-containing disinfectant to enhance teat condition. Iodine and lactic acid are commonly used in post-milking disinfection to lower the occurrence of clinical mastitis [38, 47]. After removing clusters and post-milking teat disinfection, the milker should open the row exit gate. This also ensures easy access to and exit from the milking parlour and reduces filling delays between rows. After the last row of cows has exited the parlour, a prompt washdown and plant sterilisation should be performed to reduce faecal contamination of the milking areas [38].
2.6 Water
Bacteria-contaminated water can also raise milk bacterial levels, compromising food safety [43, 48]. In farms with a low biosecurity plan, water can serve as a primary source of contamination, mainly if it is obtained from an inadequate open water supply [37, 49]. Unsafe drinking water is a serious health issue in many poor nations, contributing to high morbidity and death rates [48]. Therefore, a steady supply of clean, cold water is required for the production of high-quality milk. Water used in cleaning and rinsing milk equipment and handling containers must be of the same safety and purity as drinking water. Milking tools that have not been fully cleaned and sanitised may be the source of numerous germs that turn high-grade milk into an unsatisfactory product [4, 50].
3. Milking parlour hygiene
3.1 The hygiene of milking parlour
Hygienic situations vary depending on the production system, appropriate practices, level of awareness, and availability of resources. To prevent pathogen proliferation in dairy farms, milking parlour surfaces should be cleaned and disinfected twice daily. The cow milking parlour is a separate location for collecting the dairy farm’s final output—raw milk. The milking parlour’s design, location, milking equipment, proper hygiene, and working practices must all work together to reduce the danger of milk contamination through the environment and milk contact surfaces. The milking area must be located and built in accordance with food safety regulations to maintain sanitary conditions during milking.
To limit the possibility of contamination, the milking parlour should be designed with adequate sanitation and a high degree of pest control (flies, birds, or other animals). There must be appropriate separation from the premises where the cows are housed. Cleaning the milking parlour is part of the dairy farm’s normal program, and all surfaces and component elements of this must be washable and resistant to the action of disinfection agents in order to achieve an ideal degree of cleanliness. The surfaces of the doors, walls, and floor must be easy to clean, smooth, and composed of waterproof materials. To minimise contamination during milking, the floor must allow for appropriate drainage of the remaining water.
After each milking, all components of the milking station should be cleaned. A supply of potable water must be provided to guarantee adequate water pressure and temperature. The circulation of air and ventilation velocity inside the milking parlour is critical for avoiding contamination from moisture [51].
3.2 Milking equipment hygiene
The design of milking equipment must minimise the danger of milk contamination. The milk contact surfaces must be simple to clean, disinfect, and keep in good shape. For these goals, they must all be made of washable, non-toxic materials that are resistant to the action of disinfection agents [52]. Cleaning the milking equipment is done to avoid microbial contamination of the milk. The cleaning technique must be conducted after each milking to remove milk residues, organic residues (fat, protein, lactose), and mineral residues (milk stone, limescale) from surfaces, as well as killing or decreasing bacteria to an appropriate level (disinfection) [53]. To prevent milk residue from drying on equipment, the entire milking system must be cleaned off at the end of the milking stage. Water washing readily removes the majority of milk residue (95%). Organic milk traces (fats, proteins) and/or the milk stone might remain on the cleaned surface, potentially protecting microorganisms by forming a biofilm [54].
Many factors impact cleaning performance, including water hardness, water temperature, flow velocity of water, chemical component concentration, and contact duration. Water is a critical component in the cleaning of milking equipment since it is part of the cleaning solution, has a mechanical impact on the surfaces to be cleaned, and ensures the ejection of milk residues (discarded water). The mineral composition of the water (calcium, magnesium, iron, and so on) as well as other dissolved components affect the performance of cleaning and disinfection chemicals. Water hardness is an essential quality indicator of water in terms of cleaning action performance. Water hardness affects the cleaning ability of detergent agents and allows the production of biofilm on surfaces if it is too high. The biofilm provides excellent protection for thermoduric bacteria.
Cleaning agents are divided into two types: detergents and disinfectants. To save time, the detergent can be used with disinfectants such as chlorinated alkaline or peracetic acid. Cleaning agents are alkaline chemicals that dissolve organic milk residues and acid compounds that dissolve mineral milk residues to prevent calcium and magnesium cations from creating milk stone. Enzymatic detergents are non-alkaline detergents that contain enzymes that work on a particular substrate (organic milk residues). Typically, alkaline detergent is used as the primary detergent. Once a week, acid detergents might be used to eliminate milk stone. They must all be authorised for usage in the food sector [54].
Disinfectants are used to destroy germs, reducing the number of bacteria on milk contact surfaces to a negligible level. Cleaning chemicals may contain adjuvants such as sequestering and chelating compounds, which interact with various water minerals such as calcium and magnesium to prevent them from precipitating out of solution and creating milk stones on the contact surfaces of milking equipment. Wetting agents, or surfactants, are another effective adjuvant because they reduce the surface tension of the cleaning solution and allow contact with the milk leftovers to remove them.
In dairy practice, the combination cleaning chemical (detergent-disinfectant) is most commonly used. The cleaning of milking equipment is divided into three stages: prewashing, main wash, and final rinse. All direct contact surfaces (hoses and other elements of the milking equipment) must be prewashed (first rinsed) with fresh warm water (40–maximum 50°C) immediately after milking to eliminate the majority of milk residues. This cycle should be repeated until the wasted water has a clear appearance (physical cleanliness). The temperature of the water is the most critical aspect at this step to avoid the solidification of milk lipids on the surfaces (when the temperature is too low) or the “baking” of milk protein (when the temperature is too high).
The primary wash (circulation cleaning) is a thermal and chemical treatment designed to remove milk residues (mineral and organic residues) and decrease bacteria on pipes to negligible levels. It uses hot water and a cleaning solution.
The capacity of milk residues to dissolve and emulsify is affected by the temperature of the water. Detergents are more easily dissolved in warm water. To avoid the production of fatty coatings (when the temperature is below 40°C) and protein denaturation (when the temperature is too high), the temperature of the washing water should be 65–80°C at the start and 40–50°C at the end of this stage.
The alkaline washing cycle is used to remove organic milk residues (e.g., lipids and proteins) that are breaking down and floating in the wash solution. The effectiveness is proportional to the alkalinity of the cleaning solution, which must be between 250 and 500 ppm (e.g., Na2O) [54].
On the other side, the acid washing cycle is performed to eliminate the mineral residues from the washing water and from the contact surface of the milking equipment with acid solutions (pH 3–3.5). Efficiency, as the frequency of the acid washing is in direct relation to the quality of the water. For this step, warm or lukewarm water could be used. The water rinse step shall be set between chemical cleaning cycles to remove residual cleaning chemicals and to avoid the mixing of alkaline and acidic substances. The last rinse is used to eliminate any cleaning solution residues (chemical cleanliness). It employs cold or lukewarm water for this purpose. The wasted water is drinkable until the end. “The last glass of (post-rinse) water coming out of your system should be drinkable!” [55].
Two additional stages, such as a rinse stage after washing with detergent and subsequently a disinfection circulation, must be set up for cleaning systems that use detergents and disinfectants separately. A final rinse will be performed after the disinfection. As part of appropriate hygiene practice, milking equipment is disinfected or sanitised to reduce germs to negligible levels or eradicate microorganisms that may persist on surfaces (the microbiological hazards). This is a preventative strategy to avoid milk contamination during the subsequent milking stage, and it is designed to be used on clean surfaces (no milk residues). Because of their effectiveness against Gram-positive and Gram-negative bacteria, as well as some viruses, chlorine compounds such as calcium hypochlorite and sodium hypochlorite are the most commonly used. Because active chlorine interacts with and is inactivated by milk organic residues, disinfection with chlorine compounds must be undertaken on clean surfaces. Except for the cleaning procedure, which employs a combination of cleaning product detergent-disinfectant, chlorine disinfection is frequently set up as a pre-milking phase [56].
Acid disinfectants, such as acid-anionic surfactants (often an anionic detergent and phosphoric acid) and organic acids (e.g., propionic acid, acetic acid, and lactic acid), work as both milk stone removers and disinfectant agents. Potential organic milk residues on surfaces do not affect their functions. There are several advantages to utilising acid cleaning chemicals, including the fact that they are most effective on stainless steel surfaces, are heat stable up to 100°C, and have an efficient action against a wide variety of vegetative Gram-negative and Gram-positive bacteria.
Cleaning systems might be operated manually or mechanically. In a manual cleaning system, the operator is responsible for the whole operation and management of the cleaning process, including the preparation of the cleaning solution, controlling the volumes of hot and cold water, and determining the duration of the circulation cleaning phase. In comparison, the cleaning unit ensures the majority of activities in an autonomous cleaning system, with just a tiny portion of these still requiring manual intervention. Clean-in-place (CIP) is a typical way of cleaning pipes and other elements of milking equipment, including the bulk tank. A suitable cleaning system maintenance program is established regularly, at least twice a year, to guarantee effective cleaning with an impact on the sanitary quality of milk.
After the final rinse, the whole milking pipeline, including the supply line, is drained. Gravity generally provides drainage since milking tubes are typically too short to have a sufficient slope. Gravity action may be inadequate to provide an effective drain in rotating systems such as round-the-shed milking parlours; thus, a supplemental means, such as sponges pushed down the pipes to drive the remaining water out of the system, is required. The sponges are injected manually or mechanically into the system and must be withdrawn manually at the end. The final element of the cleaning program for the round-the-shed milking parlour is drying, which is accomplished by blowing air through the whole pipeline system [56].
The milk cooling tank is cleaned using the same techniques as the milking equipment: prerinse, primary cleaning, final rinse, and disinfection. The greatest danger is psychrophilic bacteria, which can grow quickly at temperatures ranging from 1 to 10°C). The milk transporter is used for lukewarm water rinses that occur shortly after the milk is removed; rinse water temperature should range from 30 to 50°C. During the primary wash cycle (thermal and chemical processes), the cleaning solution temperature is set at 50°C. The final washing of the cooling tank with cold or lukewarm water is critical to ensuring the elimination of all residues. It is finished with acidified water, which neutralises and eliminates detergent and mineral residues. Disinfection is done soon before the next milking, allowing enough time for disinfection agents to drain before filling. Depending on their size, cooling tanks can be cleaned manually, with CIP or mechanical methods, or both.
The robotic milking systems (the stationary or mobile AMS) are designed apart from the cow house area to safeguard the entire installation from contamination. The AMS platform is constructed, maintained, and cleaned in such a way that waste accumulation is minimised. It has a solid floor and a plumbing drain trap connected to a wastewater system for this function.
All utilities are required to ensure good manufacturing and hygienic practices, such as proper lighting to perform equipment checks and maintenance, sources of hot and cold potable water with an optimum flow rate, proper ventilation, and effective pest control to prevent birds from nesting. All direct milk contact surfaces and AMS exterior surfaces must be cleanable. The AMS platform is outfitted with essential facilities and supplies for hand hygiene (washing, disinfection, and drying), as well as cleaning utensils and the surrounding space (hoses). Because an automatic milking system replaces the milker, it includes automated cleaning and milking gear. The automated milking system is thoroughly cleaned (including disinfection) at least three times every day, at around 8-hour intervals. All contact surfaces of the automatic milking system, including the cleaning agents, are cleaned in accordance with the manufacturer’s cleaning guidelines. As a precaution, it established a brief rinse cycle between two consecutive milkings to limit the danger of infection transmission from cow to cow [57]. It initiates a water washing cycle for all milk contact surfaces of AMS and hoses that have been inactive for more than 40–50 minutes, followed by emptying.
The AMS buffer tank is cleaned promptly after each emptying, and it must be cleaned or sanitised again within a few hours of the next milk pickup. The outer surfaces of AMS, including the floor and milking platform, are cleaned regularly and maintained clean. The milking equipment maintenance program is critical to ensuring the proper operation of AMS, including cleaning procedures. A proper maintenance program must always be followed to ensure the proper operation of an AMS [53].
3.3 The efficiency of the cleaning process
Cleaning milking equipment might be regarded as a significant element in terms of raw milk hygiene [58]. Given that milking is a regular habit (at least twice per day), visual inspection is the measure used during and after cleaning to ensure that the overall efficiency of the cleaning and associated routines is at a satisfactory level. The monitoring technique comprises measuring water temperature, assessing water flow, and evaluating surface cleanliness. The temperature of the washing water may be verified using a conventional thermometer (for manual cleaning) or a temperature sensor and a display for the cleaning machine. Only transparent portions of the milking equipment, such as milk metres, clusters, pipes, and the receiver, are used for visually inspecting water flow.
The visual assessment of surface cleanliness, as a preoperational control before milking, detects leftover residues in the case of insufficient washing, or it may reveal a probable fault of the machine. In most circumstances, insufficient cleaning may be feasible in certain areas designated as difficult-to-clean. The sanitary quality of milk can be impacted by improperly cleaned milking equipment, inadequate milk chilling, inappropriate teat and udder washing, the health of the udder, and so on. As a result, other methods of assessing cleanliness must be established, such as the Standard Plate Count (SPC), the colony count of mesophilic bacteria growing under aerobic conditions, which is used to determine the bacterial quality of bulk tank milk but is not as useful in identifying the source of bacterial contamination. A more specific parameter, which is directly related to cleaning efficacy, is the identification of the presence of thermoduric bacteria on the surface of milk equipment, particularly in areas with a cracked surface (old, cracked rubber), and the survival of milk pasteurisation if cleaning is inadequate [58, 59].
It has been demonstrated that failing to maintain sufficient hygiene contributes to milk contamination with undesired or pathogenic microorganisms as well as chemical or physical dangers. Poor cleanliness contributes to more germs, causing milk to deteriorate quicker. To keep raw milk fresher for longer, practice proper cleanliness both while milking and when handling the milk afterward [60]. The efficiency of the cleaning process can be influenced by the maintenance of equipment, milking technique, and milking management.
3.3.1 Maintenance of equipment
A static (without milking cows) and dynamic (while milking cows) test should be done on the milking equipment once a year. A dynamic test assesses the milking process by machine and farmer, and hence only this test provides a comprehensive picture of the milking process’s functionality. The frequency with which teat cup liners should be replaced varies according to the type: rubber and silicone teat cup liners should be replaced after 2500 and 10,000 milkings, respectively [61].
3.3.2 Milking technique
Before milking, the farmer should wash, sanitise, and disinfect his or her hands and/or use gloves. Teats should be thoroughly cleansed with a clean towel before milking. Teats should be dried following disinfection if they are also cleaned before milking. After removing the teat cups, the teats should be sanitised. A visual examination of the foremilk is recommended. After milking, the milking equipment and parlour should be cleaned. Milking equipment should be sterilised between cows, ideally using steam or water heated to 75°C. After milking, the milking equipment and parlour should be cleaned [61].
3.3.3 Milking management
Cows should be milked in the most comfortable and hygienic conditions possible. Rubber mats or a similar surface should be included in resting places when cows are kept in stables with slatted floors to prevent cows from lying down on the slatted flooring. Cows with chronic subclinical mastitis should be removed from the herd, and a microbiological investigation of all cows’ udders should be performed at least once a year. All lactating cows should have their flanks, udders, and tails clipped. To reduce stress, the cows’ hierarchical order should be followed, although unwell cows in lactation (e.g., mastitis) should be milked last. The teat holes stay open for 30 to 60 minutes after milking. It is thus advisable to leave the cows standing for at least 30 minutes after milking. This can be aided by supplying new feed at the feeding fence [61].
4. Conclusions
Whether the cows are milked by hand, mechanically, or automated, biosecurity and good hygiene are necessary. Milking biosecurity should be a part of a farm biosecurity program designed to increase herd health, welfare, and production. The milking biosecurity plan must be monitored and assessed in order to identify all risks of udder and milk contamination. The milking biosecurity plan should be decision-focused and tailored to the individual circumstances of each dairy farm. Many of the difficulties experienced can be avoided or mitigated with the assistance of veterinary services. Also, staff and visitors should be taught about biosecurity precautions used on the farm. Milking parlour hygiene necessitates that the milker’s hands and clothes be clean, he or she be in excellent health, and the milking machine and milk storage equipment, such as milk churns, be maintained clean and in good working condition.
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