Biosecurity - an essential tool for modern poultry production

By Chris Morrow, Company Veterinarian, Aviagen - Biosecurity is defined as, "the prevention (or control) of pathogenic microorganisms from contacting animal populations." It is essentially keeping the bird separate from the bug.
calendar icon 20 March 2006
clock icon 9 minute read

Biosecurity - an essential tool for modern poultry production - By Chris Morrow, Company Veterinarian, Aviagen - Biosecurity is defined as, "the prevention (or control) of pathogenic microorganisms from contacting animal populations." It is essentially keeping the bird separate from the bug. Aviagen

Biosecurity Defined

Additionally, biosecurity is a tool to help minimize the effect of infections and decrease the impact of disease. Sometimes it may not be critical to diagnose the disease agent involved in a problem, but to analyse what is wrong with the biosecurity programme. Biosecurity should be viewed as part of the solution, potentially reducing the dependency on extensive testing and medications.

As such, biosecurity is primarily a management-implemented system. Initial design of a biosecurity system should include expert input from veterinarians, but implementation and follow-through is accomplished by every person involved in the production process, with ultimate responsibility resting with the farm manager. Farm managers should continually evaluate all areas of operation under their direction. Changes in protocols and procedures must be assessed for risk of introduction of pathogens. A complete biosecurity program includes proper design, training of staff, system-wide monitoring, and constant updating. See Table 1.

The concept of creating microbiological barriers to prevent pathogen transmission is the basis of biosecurity. It is good if the effectiveness of the barrier can be monitored. Monitoring can either be qualitative (for example, the presence or absence of Salmonella) or quantitative (for example, bacterial surface counts). Monitoring of surface bacterial counts in hatchery and on farm after cleanout are typical examples of monitoring biosecurity effectiveness. See Table 2.

Pathogens can be roughly broken into two classes; those with vertical transmission and those with only horizontal transmission. The independence of the day old chick from its mother after hatch allows poultry production to completely separate generations and stop horizontal transmission of pathogens between generations. This gives the poultry industry a great advantage over other animal industries. A managed system of egg hygiene, handling and hatchery operation is needed to stop movement of pathogens between generations by horizontal transmission. Only true vertical infections will come through a hatchery with a good biosecurity programme.

It is important to understand in the objectives of a biosecurity programme that control of all infections may not be practical. For example, the installation of filters on incoming air is not practical in most situations. Also all biosecurity barriers need to equally effective, otherwise the expense of implementing heat treatment of feed will potentially have no impact, due to a weak link in the system.

A simple model looking at possible sources of Salmonella for a poultry flock.
A barrier put at each stage will protect the flock.

Initially, biosecurity begins with the physical layout of the farm and the production cycle. Production sites should be isolated from other production facilities so that if problems occur, spread is minimized. Sites with feed mills', breeders, broilers, rendering plants, slaughterhouses and hatcheries offer some economies in organization but make the implementation of effective biosecurity very difficult.

"All in - all out" strategies effectively stop the carry over of fragile pathogens on a site. This effect is further enhanced by modernized facilities and effective cleaning and disinfection. Placing flocks of single-ages helps to control disease problems by reducing bird to bird passage from vaccine strains.

However, effectiveness of geographic isolation can be undone by contact from flocks in the rest of the operation. Feed delivery, bird transport and egg collection should be a biosecure process. Sharing of equipment and staff between farms should be avoided, but if it occurs, efforts should be to organize the process in a biosecure way. Management practices like spiking (introduction of new males into an older flock) and thinning of broiler flocks (partial depletion) need to be conducted with biosecure methods. Transport crates need to be washed and disinfected after use, and auditing should be conducted on a regular basis, by appropriate personnel.

It is important to verify control points where flow of pathogens could be reversed in the production process, and implement barriers to prevent back-flow of pathogens (washing of egg trolleys, trays, crates, transport etc).

The distances between farms to prevent transmission of airborne infections is not known and is influenced by climate, wind direction and the actual pathogen under consideration. Mycoplasma synoviae appears to be more infectious between farms by airborne route that M. gallisepticum. Certainly flocks should be more than 400 m and preferably over 2 km apart. The size of the infected source flock (and receiving flock) also influences the risk of contamination. Large infected flocks 500m from a site are more risk than 5 backyard chickens at the same distance. Two kilometres is recommended as a minimum distance from parent stock flocks.

Cleaning and disinfection are important parts of a biosecurity programme. Cleaning is the most important aspect; the physical removal of contamination. Litter and other contaminated material needs to be removed from the farm to maximize the effectiveness of "All in - All out" strategies.

Specification of stock and other biologicals for introduction to farming base

The sourcing of stock from flocks with known health status is important. Aviagen broiler breeder stock is supplied free of infections known to cause problems by vertical transmission (M. gallisepticum and M. synoviae infection confirmed by a routine monitoring programmes, free of exogenous ALV infection and free of Salmonella pullorum, S. gallinarum, S. typhimurium and S. Enteritidis). The stock will be delivered with maternal antibodies for REO, CAV, AE and IBD and have been vaccinated with an effective Marek's vaccine at the hatchery.

Similarly live vaccines should be free from contamination especially with ALVs, REV, EDS-76 (and the vaccines need to be effective). This is a responsibility in most countries of government authorities but contamination can occur. Suspected problems need to be investigated by independent laboratories. Breeding stock is very valuable and saving money on vaccines is not always advisable.

Other potential sources of infection

Feed should be manufactured in a hygienic way and kept biosecure until delivery to the birds. Microbiological quality is best assessed by selective salmonella culture of all raw materials entering the mill and epidemiological connections to salmonellas found in the breeder and broiler flocks and products.

Staff training on biosecurity is needed. This includes production staff, management staff (including the owner and CEO) and trades people. Staff having contact with birds at work should not be allowed to own birds at home and be discouraged from contact with other birds. Training and auditing is needed on cleaning and disinfection of sites.

Latrogenic problems with administration of vaccines need to be prevented by further training. Sterile technique in the making up and administration is important. Contamination of vaccination procedures in the hatchery can cause problems like mortality and femoral head necrosis.

New litter needs to be considered as a source of infection. It should not be stored on the floor or outside. It should be covered or in plastic bags. Many poultry integrations have wood shavings made specially and bagged (25 kg) for use rather than obtaining sawdust as a by-product. Rice hulls and other materials are used for litter in so other parts of the world but it is difficult to assess the risk of these materials to the biosecurity of our flocks.

Rodent control and the exclusion of wild birds also require consideration. Making the shed unattractive to rodents and wild birds is the first step. Feed (and stored litter) should not be accessible to rodents or wild birds, the sheds should be well maintained. Insulation in panel sheds is often an attractive rodent house. Other animals should not be allowed in the sheds.

The advantages of biosecurity include the setting up of a sustainable production system that does not depend on routine administration of antibiotics (cost saving and no problems with antibiotic resistance or residues). This capital cost may look considerable if your current farm base is a multi-age site but if the ultimate aim is kept in mind during planning for future expansion, single-age may be possible. The only way to convince the owners or management of the value of single age site is to make the talk in terms of money. What savings can be made with a new farm organization? Savings on antibiotics, vaccines, liveability and expected improvement in performance needs to be quantified and compared to capital costs.

Biosecurity during an health-status-upgrading-process

In operations that are currently infected with an undesirable infection there will need to be a plan to eliminate or control that infection. The usual method is to accurately classify all flocks into infected (Dirty) and uninfected (Clean) and then put extra controls to stop the infection from moving between dirty flocks to clean flocks. This may involve more intensive monitoring of clean flocks, barriers between clean and dirty flocks and where appropriate, strategic medication or vaccination of dirty flocks to decrease the number of pathogens in these flocks and decrease the likelihood of horizontal transmission. Good quality laboratory testing is needed.

Biosecurity systems also need to be able to cope with breakdowns in biosecurity. Again the clean/dirty principle can be applied. Traceability at this stage becomes very important for containment of the problem and working out the probable source of the problem.


Biosecurity is based on the simple idea that disease can not occur if the pathogen that causes the disease is not present at the right time. Horizontal transmission is easier to prevent, and should be the focus of an effective biosecurity program. Vertically transmitted infections can give us more problems but the control or eradication of these infections is the primary responsibility of the primary breeders. Veterinarians in the poultry industry have the responsibility to make sure that infections are not introduced into stock from vaccines (general biosecurity and the use of suitable quality vaccines).

This struggle to exclude pathogens is the responsibility of everyone involved in the production process: from the feedmiller to the company electrician, from the veterinarian to the egg collectors, from the crate wash operators to the truck drivers. Training to make staff understand biosecurity and documentation of biosecurity protocols is essential. Critical review of these processes by everyone involved and external audit is needed continuously.

Finally, the rewards of a sound biosecurity system are a poultry production system well protected against known and unknown health threats, lowered risk of evolving resistance to current medication, and a sustainable production system.

Source: Courtesy of Zootecnica Russian Edition - March 2006

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