Current knowledge and application of biosecurity in cattle

• Milking cluster: Rinsing of the milking cluster, ideally after every cow, helps avoiding spread of infection between cows during milking.

1. What is biosecurity?

Biosecurity is defined as the combination of all measures that can be taken to reduce the risk of introduction and spread of disease agents between animals. As such, the implementation of biosecurity is an important tool to accomplish disease prevention on cattle farms. It contributes to animal and public health and welfare, but it can also improve economic results and lower antimicrobial use and resistance.

As a concept, biosecurity can be divided into external and internal biosecurity. External biosecurity concerns the risk of introducing infection on the farm. Internal biosecurity aims to avoid spread of infection between different animals and groups within the farm. Next, the different categories and their corresponding biosecurity measures are elaborated upon, based on the chapter concerning cattle biosecurity in the book “Biosecurity in animal production and veterinary medicine”.

2. External biosecurity

External biosecurity comprises all measures taken to prevent introduction of infections on the farm. Through the external biosecurity measures one tries to shield the farm from pathogens in the outside world.

Purchase of animals. The introduction of new cattle through purchase is by far the most cited risk factor for introduction of disease pathogens in a herd. Therefore, avoiding purchase is often considered the most efficient biosecurity measure. Although the risk of introducing pathogens depends on the frequency of purchase and type of purchased animals, all purchase involves risk, which should be mitigated to the utmost.

Whenever the purchase of cattle is necessary, e.g. a breeding bull or some female youngstock, measures to avoid disease transmission through direct and indirect contact should be applied.

  • Purchase from a safe source

The risk of disease introduction can be reduced by purchasing cattle from farms with a sanitary status and health management that is equal or higher to that of your own farm. When your farm has a specific pathogen free (SPF) health status for a disease [e.g. infectious bovine rhinotracheitis (IBR) or bovine viral diarrhea (BVD)], it is advised to purchase cattle from farms with the same or a higher status. This status can be included in the animal health register of the farm. Farm-level tests may in some cases complement or substitute the register, e.g. ELISA or PCR tests for the presence of Mycoplasma bovis in bulk tank milk.

  • Limit the number of animals purchased

Limiting the number of animals purchased and the number of farms of origin where cattle are purchased can reduce the risk of disease introduction. In particular, for veal calf farms, this can pose a problem, since the animals originate from many different farms. In such cases calves could be divided in smaller risk groups, depending on one or more specific disease statuses as discussed further.

  • Test the animals before arrival

Even when cattle are purchased from farms with a sanitary status and health management that is equal or higher than your own farm, the individual disease status of the purchased cattle should be checked by testing the animals, preferably at the farm of origin. In this way diseased animals do not enter the farm. In testing, a selection of diseases must be made, which remains a risky venture. Tests for IBR, BVD, tuberculosis and Johne’s disease are of high importance and thus often performed. One should realize that cattle can be carriers of other disease agents (e.g. Mortellaro disease, Psoroptes ovis mange, Staphylococcus aureus mastitis, Q fever) than those few tested for. Testing a milk sample of lactating and pregnant cattle is advised. Calves of purchased pregnant heifers and cows should be quarantined and tested immediately after birth as e.g. BVD can be transmitted through the placenta. Calves purchased can be tested for sufficient maternal immunity. However, the disease-free status of the animals is never 100% certain.

In case no thorough selection can be made or high numbers need to be purchased (e.g. veal farms or feedlots) all information discussed above can be used to divide animals into high and low risk groups. Similar risk groups can then be quarantined or housed together.
Several diseases can spread through venereal contact and the use of natural service to fertilize the cows is a risk factor for those diseases. For example, Leptospira hardjo can be found in infected bulls’ sperm for several months. This risk can partly be contained by testing all genetic material entering the farm. Animals temporarily brought onto the premise for fertilization should be avoided.. Risk can be further limited by using artificial insemination instead. Also when purchasing sperm, embryos or colostrum attention should be paid to the health status of farm/institution of origin.

  • Be careful with transport

When cattle are transported to the farm, only the cattle destined for the farm should be present on the transportation vehicle. During transport, carrier animals shed more pathogens such as Salmonella spp. due to stress, possibly infecting animals with a different destination. Animals should be transported directly from the farm of origin. On markets or in salesmen’s stables and even trucks, they might directly or indirectly have contact with other animals. When using your own transportation vehicle, you also control the cleaning and disinfection status of the vehicle.

  • Quarantine new arrivals

Once purchased cattle arrive on the farm they should be quarantined, i.e. the animals are placed in isolation without contact with the herd for a sufficient period. Quarantine allows the introduced animals to adapt and avoids transmission of disease to the herd. The recommended quarantine length varies, but usually three to four weeks is advised. Quarantining purchased cattle cannot be replaced with only testing, neither is quarantine effective for detecting seemingly healthy carrier cattle.

An appropriate quarantine area is a space that prevents disease transmission through direct and indirect contact (e.g. aerosols). Therefore, a quarantine area should be a separate building where no other cattle is present. If no dedicated building is available, a pasture or an old premise can also serve as quarantine area. Furthermore, one should also take into account that a quarantine period of three to four weeks is insufficient for diseases with a long incubation period, e.g. Johne’s disease; and when purchasing lactating cattle, these should be milked inside the quarantine area or milked last.
Specific clothing and boots (and/or a disinfection footbath) should be available at the entrance of the quarantine area and can only be used for this purpose. Preferably hands are washed when entering and leaving the quarantine area. In their daily routine, farmers should enter the quarantine area at the end of their working scheme. After a quarantine period is finished, the quarantine area should be well cleaned and disinfected. It should remain empty until dry before new animals can be added. Specific material (e.g. feeding utensils) should be available in the quarantine area.

A black rodent box filled with poison to catch rodents on the farm.
  • Be careful with contests and markets

Sometimes cattle leave the farm, but come back afterwards, e.g. for auctions, contests or markets. Such animals can be infected by other animals or the environment. They should also be also tested and quarantined when they return to the farm.

Vehicles and equipment. The risk of disease transmission of vehicles depends among other things on the type of vehicle: for instance, rendering company trucks are considered a higher biosecurity risk than feed trucks. Although feed and milk collection trucks are rarely exposed to the animals on a farm, these vehicles should be considered as a biosecurity risk as they visit several herds on the same day.

It is recommended that vehicles do not enter the stables and one specific farm entrance is provided for all visitors. This parking space should be isolated from areas with animal access and separated by a sanitary transition zone. Feed should be delivered and tank milk collected without the need for the driver to enter the stables. All vehicles entering the farm should be cleaned and disinfected, and wheel disinfectant systems such as wheel baths are recommended.

When cattle leave the farm the truck is preferably empty, cleaned and disinfected upon arrival at the farm. However, often cattle from other farms are already present in the truck. Therefore, farmers are recommended not to enter the truck when loading animals and the transporter should not be allowed to enter the stables. Furthermore, cattle that leave the farm can be moved to a separate loading area to prevent contact with the herd. E.g. male calves that are sold can be housed at a different location than calves that remain on the farm.

Equipment such as a transportation vehicle or manure spreader is preferably not shared with other farms, along with smaller tools such as obstetrical and dehorning equipment. When sharing is unavoidable, the equipment should be cleaned and disinfected when returning to the farm.

Removal of dead animals. For every dead animal the cause of death may be infectious and therefore dead animals should be removed from the farm as quickly as possible to avoid disease transmission. Until the carcasses are collected by the rendering company they should be stored in a separate storage space with at least a cemented floor. Preferably this storage space is located close to the public road to avoid that trucks of the rendering company have to enter the farm and does not cross routes usually used by on-farm traffic.

A carcass storage space should have at least a cemented floor, and is preferably sealed off from other animals.

When carcasses are manipulated the use of disposable gloves and/or cleaning and disinfection of the hands afterwards is recommended. Furthermore, cleaning and disinfection of the storage place after each use is advised. To avoid disease transmission through rodents, cats and dogs the storage place should be sealed off. Ideally, waste water must be collected.

Professional visitors and personnel. Cattle farms are very often visited by professional visitors. Professional visitors enter farms for work-related reasons and may hereby come into close contact with cattle. Besides veterinarians, other professional visitors are for instance the AI technician, the cattle salesman, the feed supplier, the milk collector, the rendering company, the hoof trimmer, other farmers and possibly also other caretakers (personnel). Other visitors, e.g. a school visit, are considered lower risk, yet should not be ignored.

It is recommended that every visitor only can enter the farm after notifying the farmer and the stables should only be entered together with the farmer. Fencing the farm and closing the entrance with a gate, making the phone number of the farmer visible and restricted area signs (pictograms) are practical tips that may help.

A sanitary transition zone to change clothing/boots an wash hands befor enteringthe stables.

Is used in combination with soap and disinfectant, bootwashers are an ideal way to disinfect farm specific boots.

Other adequate biosecurity measures for professional visitors are the use of herd-specific protective clothing and boots and/or well-maintained disinfection footbaths/footmats. Although both footbaths and –mats are effective, footmats appear to be used more correctly. Neither can be expected to mitigate the risk completely. Before disinfecting boots it is a prerequisite that they are cleaned first, therefore boot washers should be used as well (Fig. 1). Visitors should wash and disinfect their hands and/or wear gloves before entering the stables. A sanitary transition zone where visitors can change clothes and wash their hands should be located in such a way that a minimum of efforts have to be done to first access the sanitary transition zone and the stables afterwards (Fig1). Boots and clothing should be changed between age groups and regularly cleaned and disinfected, as they can be contaminated with pathogens in the stables. Brought equipment entering the stables should be treated in the same way, although only using farm specific equipment decreases the risk even more.

Every visitor or employee can represent a source of indirect transmission. In recent studies it was noticed that biosecurity measures at entrance were not implemented by all visitors, nor was this expected of every visitor in the same extent: veterinarians used protective clothing and boots more often than AI technicians, followed by cattle salesmen. Transporters and hoof trimmers for example were not expected to take the same measures (Damiaans et al., 2020).

Contact with other animals. Almost all animal species can serve as biological and/or mechanical vectors for cattle diseases and thus constitute risk for disease transmission.

  • Contact with other ruminants

Very often contact is possible with cattle from other farms on pastures shared with animals from another farm in the same season or through an adjacent pasture. For example, in the study of Sarrazin et al. (2014), on about 70% of the participating farms contact was possible with cattle from other farms. Furthermore, disease transmission between cattle from different farms is possible when they have access to the same surface water in the pastures or manure has been spread on pasture. The general rule should be to avoid pasture contact on the same or adjacent pastures. When this is not possible, double fenced pastures may reduce the risk of disease transmission. For a disease that is not transmitted through air, a distance of at least 3 meters is recommended. Even better is to pasture high risk groups on pastures with no adjacent pastures.

  • Wildlife and vermin

Rodents, insects and wild animals all may transmit disease. Rodents are known sources of salmonellosis by contaminating feed with their feces while deer and other wild ruminants are a reservoir for the blue tongue virus, transferred by mosquitoes. Insects are often overlooked, yet their ability to transmit disease is well known both as biological and mechanical vectors. For example, flies can mechanically transmit cryptosporidiosis for up to three weeks and are the main transmission route for Moraxella bovis,

To avoid disease transmission through these animals, their access to the stables, manure storage facility and food storage facility should be limited as much as possible by closing or shielding doors, windows and gates. Perimeters can be fenced and spilt food should be removed immediately. Rodent and insect control programs are indispensable tools to keep the farm vermin free. Insects can be combatted by using insecticide on the animals and environment, but also by habitat control, waste management, elimination of still water, etc. Cats are not considered a good rodent control program and traps and/or poison are recommended to control rodents.

  • Pets

Domestic cats and dogs are very often present. Similar to wildlife and vermin, they can transmit disease to cattle as biological and mechanical vectors (e.g. neosporosis, leptospirosis) and their access to the stables, manure storage facility and food storage facility should be limited as much as possible by closing or shielding doors, windows and gates. Dogs are well known biological vectors of neosporosis, while cats are mechanical vectors of tuberculosis, salmonellosis and Q-fever among others.

Some tips on vermin and bird control are given in this video:

Feed and water quality. The quality of feed and water is important to reach a sufficient intake of both feed and water. If the feed or water has a low palatability, intake will decrease resulting in diminished growth and production.

A myriad of bacteria may be present in animal feed. Though most of these bacteria cause no harm to animal health, a select few may cause disease. For example, Escherichia coli, Salmonella spp. and Listeria monocytogenes are known to transmit through feed. Mycotic agents may contaminate feed as well. Contamination of feed can occur at all stages of feed production and storage. Crops can be contaminated with manure during fertilization of the crops or even neighboring pastures. Therefore attention should be paid when manure from other farms is used close to own crops or pastures. Furthermore, carrier animals may contaminate feed, so left over feed should not be fed to youngstock. Feeding utensils, equipment and troughs should never be used to handle manure or carcasses. Effluent of manure should not be able to contaminate the feed.

The importance of clean water is often underestimated. Several foodborne pathogens such as E. coli and Salmonella spp. can regularly be found in water sources due to contamination with feces. Contamination of water can occur at the water source, in a reservoir or pipes and at the outlets. Its quality should be tested at least once a year by bacteriological and chemical analysis. Water sources should be checked and cleaned regularly to avoid contamination with feces, urine and feed.

3. Internal biosecurity

Internal biosecurity comprises all measure taken to prevent spread of infections within the farm from one group of animals / age category to the other.

Calf hutches can be moved to another space on the farm regularly to ensure a clean surface, next to clean hutches.

Health management. Separation of sick animals from susceptible, healthy animals is one of the most important measures to eliminate disease transmission. Infected animals should be detected, isolated and treated as soon as possible.

A hospital pen is a space where infected animals are housed and isolated to prevent disease transmission towards other animals in the herd. A hospital pen should be fully separated from the other stables and diseased animals should remain in the hospital pen until fully healed and no longer shedding. An all-in/all-out system should be used and after each use the hospital pen should be cleaned and disinfected. Similarly as entering the quarantine area at the end of the daily working scheme, diseased animals should be taken care of after the healthy animals. Also the use of specific clothing, washing of the hands before and after contact with diseased animals and specific material only to be used in the hospital pen, is strongly recommended.

Cattle that have aborted should also be considered as sick animals and therefore housed in the hospital pen until the reason for abortion has been determined.
When lactating cattle is diseased, it is advised that they are milked in the hospital pen or, when this is not possible, as last in the regular milking facility to avoid contact with the healthy animals. In case of the latter option, special attention has to be paid to the cleaning and disinfection of milking material that is also used for healthy animals.

Chronically infected animals are a continuous source of infection and produce suboptimally. For some of these diseases, e.g. Mycoplasma bovis and BVD, a carrier state exists, a state of permanent infection without clinical symptoms. This type of animals are often kept in the herd, but this practice should be discouraged. Instead they should be removed from the herd immediately.

Vaccination can be considered a biosecurity measure as it reduces infection pressure by rendering animals immune, reducing the duration of infection and pathogen shedding.
Whenever treating or vaccinating animals needles should be used only once and then disposed of to avoid iatrogenic transmission of diseases such as BVD and Lumpy skin disease.
It is also strongly advised to have a register with animal health data to have an overview of the health and treatment status of individual and groups of animals. Such a register can contain the following information:

  • Disease status of the herd for known cattle diseases;
  • Current treatments;
  • Recurring diseases and its victims;
  • Possibilities and protocols for vaccination, monitoring, diagnosis and treatment;
  • Udder health of lactating cows.

This system must be regularly reviewed to detect presence of disease. Furthermore, information should be gathered from other sources for disease detection as well, such as routine necropsies and samples of dead and diseased animals, and slaughterhouse reports on post-mortem lesions.

Calving management. The period around calving is known to be critical for the dam, which experiences a temporary decrease in immunity, and for the new-born calf, which is born without acquired immunity. Therefore attention should be paid to the calving management to avoid disease transmission through direct and indirect contact.

A maternity pen is a space where the dam is housed shortly before and after calving and should never be used to house sick animals. In the maternity pen there should be no physical contact with other cattle, although visible contact may be recommended to avoid stress. Though more expensive, labor-intensive and not well implemented, individual maternity pens serve best. One individual maternity pen of approximately 14 m2 should be available per 25 cows. New born calves are easily contaminated in the maternity pen. Group maternity pens facilitate this process by increased contact with other dams directly and indirectly, especially when not cleaned after calving. Whether individual or group, before and after each calving the maternity pen should be cleaned and disinfected.

If a dedicated quarantine area is not available, creative solutions can be found, such as separated pasture, an old stable or even unused horse stables.

When calves cannot be born through natural calving a caesarean section has to be performed by the veterinarian. For this type of calving similar biosecurity measures apply: a separate, clean and disinfected space without contact with other cattle and the use of herd-specific clothing by the veterinarian.

It is recommended that the farmer is always present at the moment of calving. Hands, together with all obstetric material, should be cleaned and disinfected before and after each calving. All measures described for avoiding indirect contact in both quarantine area and hospital pen are applicable to the calving pen as well. Before a natural calving; the dam is prepared by cleaning and disinfecting the udder and vulva. After calving the fetal membranes and tissues are removed from the calving area and calf. Attention has to be paid that especially dogs do not eat these membranes and tissues.

Immediately after birth the navel of the calf is dipped with a fresh disinfectant in a clean vessel. The calf should be removed from the dam within an hour.

Calf management. Since calves are born without acquired immunity, the ingestion of sufficient maternal antibodies through colostrum within the first hours of life is crucial. Failure of passive transfer should be avoided at all cost. The administration of colostrum should fulfil the following requirements:

  • A sufficient amount of colostrum has to be administered, i.e. 200 grams Ig G antibodies. A minimum of 4L colostrum is often recommended, assuming 50 grams of antibodies per liter, although testing and confirming its quality is better. Colostrometers and densitometers are most practical to use on farm.
  • The best quality colostrum is obtained from the first milking and immediately after calving. Fresh colostrum is preferred over frozen colostrum as cellular components do not survive the freezing. However, a frozen reserve is desirable in case the dam provides no colostrum. Frozen colostrum should be thawed au bain-marie in warm water of 40-45 °C.
  • Colostrum should be harvested and conserved hygienically. It is recommended to pasteurize it (for 60 minutes on a temperature of 60 °C) to avoid disease transmission. Pasteurized colostrum leads to a higher gut absorption and a higher Ig G serum concentration and prevents infection with e.g. Johne’s disease. Using colostrum from other farms is not advised, given the fact that the maternal antibodies in the colostrum of the dam or other cows present in the herd reflect the herd immunity better than colostrum from other farms and the possible transmission of pathogens through colostrum.
  • The absorption of antibodies through the gut quickly drops and therefore the required amount of colostrum should be administered within 6 hours after birth. If calves refuse to drink, it should be administered by tube.
  • Given the small capacity of the abomasum colostrum should be administered frequently to avoid that it flows in the undeveloped rumen, unless fed by esophageal tube. Between feedings colostrum should be cooled in the refrigerator.
  • Colostrum should never be pooled as contaminated colostrum from a single cow may then infect multiple calves.

After colostrum, attention should still be paid to feed management. Feeding of calves with milk unfit for human consumption is not advised, as that milk can be contaminated with pathogens and antimicrobials. Like colostrum, milk can be pasteurized on farm to prevent disease transmission through milk. An alternative is pasteurization or milk replacer.

The Biocheck tool and other information about biosecurity can be found at

All equipment for feeding or oral administration of treatments such as buckets, bottles and feeding tubes should be cleaned and disinfected after each use to prevent iatrogenic transmission of pathogens such as Salmonella spp. and BVD virus.

Housing and hygiene management. The presence and persistence of the pathogen in the environment determines the likelihood of transmission in several diseases. For some ubiquitous pathogens the pathogen load is a critical factor in the severity of clinical symptoms. Infection pressure in the environment can be minimized by good cleaning and disinfection. Cleaning and disinfection should be performed according to the seven steps:

  1. Removal of all dry matter
  2. Soaking of all surfaces with detergent to loosen the remaining dirt
  3. High pressure cleaning to remove all the dirt
  4. Drying of the surfaces to avoid dilution of the disinfectant in the next step
  5. Disinfection of the surfaces
  6. Drying of the surfaces after disinfection
  7. Testing of the disinfection efficacy

The full cleaning and disinfection procedure is illustrated in this video:

Newborn calves that are removed from the dam are preferably housed in individual calf boxes or hutches during the first weeks of their life without physical, but with visible contact with other calves. Hutches should contain dry bedding, be easy to clean (e.g. plastic), draught-free, properly spaced (1.5m in between) and placed on a paved/cemented and easy to clean surface. The hutches should be well cleaned, disinfected and dried after the calf leaves (Fig. 2). No contact should be possible with older animals.

After use, calf hutches should be cleaned, disinfected and left to dry after occupation. Sunlight promotes pathogen death.

Calves in group housing are more exposed to pathogens. When calves leave their individual housing regrouping to group pens of the same age is advised. An all-in/all-out system should be applied at all times to avoid transmission from older to younger calves. Preferably calves and youngstock are housed well separated (i.e. no physical contact and a distance of minimum 3 meters between the boxes) to avoid disease transmission through direct and indirect contact, including aerosols and air transmission.

Working organization and equipment.

  • Age groups and specific equipment

Contact between different age groups may result in transfer of pathogens from older to naïve younger animals. Therefore age groups should be separated in a separate air space without possible contact. Age groups that should be separated can differ between farms, but should at the minimum consist of calves of zero to two months (pre-weaning), two to six months (post weaning), youngstock under two years old and adult cows. Large groups can be split in management groups.

Between different age groups, group specific boots and clothing can be changed, and hands should be washed to minimize disease transmission between groups. An all-in/all-out system should be used for all groups when possible. This system allows for cleaning and disinfection and keeps successive occupants of pens physically separated. It also circumvents the spread of disease when new animals are added to a group.

Herd specific boots and clothing, and a disinfectant basin are of high importance to avoid pathogen transmission by visitors between farms and within the farm.
  • Working lines

Sick animals and animals in quarantine should be taken care of at the end of the daily routine. It is furthermore recommended to work from young to old in the daily working scheme and not return, i.e. farm-specific working lines.

For each age group the use of age-specific equipment is advised and feeding utensils should only be used for feed, i.e. no double use for removing manure. Distinction between age-specific material or feeding-specific utensils can easily be made by labelling or color-coding the material. Preferably feeding utensils are cleaned and disinfected after each use.

Ideally a sanitary transition zone (changing clothes, washing hands) is provided for each age group of animals. The application of these biosecurity measures together with the use of age-specific material can be encouraged by providing physical barriers between the age groups. This can be a different stable, but also a bench or door which has to be passed to go to the next age group.

Dairy management. Most pathogens that are able to spread through the udder are mastitis pathogens, yet some such as the pseudocowpoxvirus and Mycoplasma bovis are not, or not solely, intramammary pathogens. Intramammary pathogens are either spread in the milking parlor (contagious mastitis pathogens), or by environmental contamination (environmental mastitis pathogens). Contagious mastitis pathogens can be transmitted by contamination of the udder or fomites in contact with the udder when not disinfected before milking and between separate cows. Environmental mastitis pathogens spread through contamination of manure, bedding and other factors in the environment. Both types of pathogens are of high importance for the dairy sector. No difference will be made between biosecurity measures as the collection of biosecurity measures stated here can be considered useful for more than mastitis pathogens only.

An optimal milking management starts with well-functioning milking equipment. A wrongly calibrated machine can cause damage to the teats because of incorrect pulsation, excessive vacuum or milking time. A yearly maintenance and control of the milking equipment should be performed by a static and dynamic test. Only by incorporating a dynamic test a complete overview of the milking process is obtained. The frequency of replacing teat cup liners depends on the type: rubber and silicone teat cup liners should be replaced after 2500 and 10000 milkings, respectively.

An optimal milking technique is another crucial factor in the milking management. The following recommendations more specifically apply to manually milking, but in general also apply to robot milking:

  • The farmer should wash, clean and disinfect hands and other used equipment before milking and use latex or nitrile gloves;
  • Teats should be cleaned drily or dried after disinfection before milking with a clean, separate cloth. Disposable cloths such as single service paper serve best;
  • Foremilk should be examined visually;
  • Teats should be disinfected after removing the teat cups to avoid infection post-milking. Though both spray and dip are acknowledged as possible disinfection, a dip is preferred as sprays risk covering only part of the teat;
  • The milking clusters should be disinfected with hot water > 75°C or steam to avoid spread between cows, ideally after each cow. Clusters should at least be disinfected after each cow carrying an udder infection, regardless whether it is clinical or subclinical;
  • The milking equipment and parlor should be cleaned and disinfected after milking;
  • Cows should be milked and kept in optimal conditions by optimizing comfort and hygiene:
  • The flanks and udders should be clipped. Several udder pathogens persist on udder skin or are environmental. All these pathogens spread less efficiently on a clean udder;
  • Animals that are infected, both clinically and subclinically, should be milked last. To be able to apply this measure, the disease status of the animal must be known and kept up to date by regular testing of milk samples and somatic cell counts.
  • If lactating cows are divided in groups, transmission during milking also can be minimized by milking the groups with the lowest risk of infection first, such as recently calved cows or cows in their first lactation.
  • After milking the teat openings remain open for about 30 to 60 min. It is therefore advised to keep the cows standing after milking for at least 30 min. This can be facilitated by providing fresh feed at the feeding fence.
  • Between milkings, the udder should be kept clean and dry.
  • When cows are housed in stables with slatted floors, rubber mats or an equivalent surface should be present in the resting spaces to avoid that cows lie down on the slatted floors.

A bacterial culture should be made of all cows at least once a year to assess the prevalence of subclinical mastitis on the farm and to know the disease status of the cows. This procedure eliminates the possibility of non-treated carrier or subclinical animals who may spread infections. Infected animals should be followed up closely. Regular (monthly or bimonthly) bulk tank milk culture can be used as an overview of mastitis pathogens on the whole farm, while somatic cell counts can indicate individual animals to keep an eye on.

Biosecurity evaluation and conclusion

It should be emphasized that the general biosecurity principles described above should be translated to advice adapted to the specific situation of each farm. As the farmer’s trusted advisor, the herd veterinarian is the ideal candidate to assist the farmer in improving biosecurity on the farm. Yet, to provide such farm specific advice, the biosecurity level of a farm should first be assessed. For this purpose, a risk-based biosecurity scoring tool is available online, the Biocheck® Cattle. It can be used for free at This objective quantification tool was developed to provide a total biosecurity score and a separate score for external biosecurity, internal biosecurity and their subcategories. With its help, a farm specific biosecurity plan can be developed that contains the farm’s disadvantages and possibilities for growth. As such, biosecurity can be improved in an optimal way by prioritizing biosecurity measures with the highest impact on the herd health. More information about biosecurity and the Biocheck® can be found at the website and in this video:


  • Damiaans, B. (2020). Investigating and quantifying biosecurity in Belgian cattle production (Doctoral dissertation, Ghent University).
  • Damiaans, B., Renault, V., Sarrazin, S., Berge, A. C., Pardon, B., Saegerman, C., & Dewulf, J. (2020). A risk-based scoring system to quantify biosecurity in cattle production. Preventive Veterinary Medicine, 104992.
  • Sarrazin, S., Cay, A.B., Laureyns, J., Dewulf, J., 2014. A survey on biosecurity and management practices in selected Belgian cattle farms. Preventive veterinary medicine 117, 129-139.
  • Sarrazin, S., Damiaans, B., Renault, V., Saegerman, C., 2018. Transmission of cattle diseases and biosecurity in cattle farms. In: Dewulf, J., Van Immerseel, F. (Eds.), Biosecurity in animal production and veterinary medicine. ACCO, 357-408.

Text and pictures: Bert Damiaans & Jeroen Dewulf

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