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Reduction of Risk in the Primary Breeder Production System

In the Primary Breeder Production System

January 14, 2008
By S.L. Gillingham A.G. Rosales E. L. Jensen C. Miller and P. Eidson


A Program for Salmonella Control.  There have been many significant advances within all sectors of the
broiler and allied industries to reduce the risk of pathogens
associated with human food-borne illness.

From a paper presented at the Poultry Service Industry Workshop in Banff, AB, in October

There have been many significant advances within all sectors of the broiler and allied industries to reduce the risk of pathogens associated with human food-borne illness. The poultry industry is under increasing consumer and regulatory pressure to guarantee food safety and meet domestic and export requirements. Public health agencies and producers of poultry meat and eggs continue to develop standards and control strategies aimed at eliminating or reducing enteric pathogens in the food chain. In this context, significant effort has and continues to be made to control the risk posed by Salmonella species at all levels of the broiler, layer and broiler meat processing industries.


This paper will review the practices used at a primary breeding company to completely control and potentially eliminate Salmonellae from the poultry production program.

Initially, Salmonella control meant preventing infections caused by avian host specific species S. pullorum and S. gallinarum (SP and SG). Subsequently this task was expanded to include the control of species that were recognized for their zoonotic disease potential (S. enteritidis and S. typhimurium).

Today, our goal is to control and eliminate all Salmonella species from the breeding program. The ability of the primary breeder to supply Salmonella free parent stock to the broiler/layer industry is a key component of this industry’s attempts to eliminate Salmonella from the finished product.

The major emphasis for preventing Salmonella infections is to avoid the introduction of these micro-organisms into the farms, hatcheries and feed mills through a robust and effective biosecurity program. This requires the establishment of barriers and the implementation of practices aimed at suppressing the most common sources of infection.

A comprehensive-integrated biosecurity program must be established as the first and most important line of defence and participation encouraged. To be effective, every employee and grower must know that it is part of their job to prevent exposure to Salmonellae, and the vertical and horizontal transmission following an infection.

An integrated-comprehensive biosecurity approach requires a strong commitment and has a significant cost. This cost should be considered an insurance policy. This approach requires routine evaluation, constant and gradual improvement, and, periodic training of employees and contract growers. Ultimately, the costs associated with these tasks will be offset by the benefit of meeting the expectations of broiler meat producers.

In our experience, the development of an effective and comprehensive biosecurity program must include a series of practices designed to reduce the risk of infection. Some of the most relevant are listed in the shaded textbox.

A comprehensive biosecurity program requires the identification of the most likely sources of salmonellae, and the establishment of practices designed to suppress the introduction and spread of these pathogens into the breeding populations.

Simple Biosecurity Model
Day-Old Placement of Breeding Stock
A critical component of any enteric pathogen control program is the placement of breeding stock free of Salmonella. The control strategies, monitoring programs and laboratory methods used at the primary breeding level follow the provisions of the USDA’s National Poultry Improvement Program (NPIP). These ensure that flocks and their progeny are Pullorum-Typhoid Clean, S. enteritidis Clean and Salmonella Monitored.

For the primary breeder, compliance with the NPIP’s provisions and all classifications for meat type birds is mandatory for all flocks and hatcheries.  Therefore, depopulation of any flock failing to meet these standards ensures the achievement of these goals. Provisions include specific testing protocols and schedules used to monitor the Salmonella status of the flocks, their growing environment and their progeny at the hatcheries.

Producers in the U.S., Canada and around the world recognize the value of obtaining day-old breeding stock from primary breeders with comprehensive biosecurity programs that are in compliance with NPIP’s health standards.

Furthermore, monitoring of parent stock chicks, meconium and or chick box liner paper at delivery has become one of the most common critical control point (CCP) procedures.

Poultry Feed
In a primary breeding operation with strict biosecurity practices, feed could be a common source of Salmonellae. Many species found during routine monitoring of the feed mill environment and feed ingredients can be found later in the environment of breeder flocks and in their offspring. In fact,  breeder flocks act as biological filters and amplifiers of salmonellae that adapt well to their intestine and internal temperature. Some species commonly found in the feed mill environment can be extremely infectious to newly hatched chicks. It has been shown that one organism of S. montevideo per gram of feed can infect a day-old chick.

Thus, an effective control program begins with the selection and routine microbiological screening of feed ingredients and the manufacturing environment. These screening procedures are useful CCPs.

Ideally, animal protein and fat sources should be avoided in the manufacture of breeder feeds. The design of the feed mill must prevent the introduction of rodents, wild birds and insects that might contaminate ingredients or finished product. The feed mill must have completely separate areas for ingredient reception and storage, grinding and mixing, decontamination by thermal treatment in pre-pelleting feed conditioners (82 to 85°C), pelleting, cooling, and the storage of the finished product.

The goal is to achieve effective partitioning of clean and dirty areas. This is achieved by physical separation and aided by air filtration systems that prevent recontamination.

Stringent rules for personnel/visitor traffic are also critical to avoid cross-contamination. Routine monitoring procedures have shown that footwear and clothing are effective carriers of dust and are potential sources of contamination. 

Hazard analysis of critical control points (HACCP) has been introduced in feed mills to reduce the risk of contamination with Salmonellae. The major CCPs include monitoring of the thermal treatment process (time, temperature, etc.), and routine microbiological monitoring through environmental sampling to evaluate levels of contamination through the different areas of the mill. In addition, samples of finished feed are periodically screened for total viable cell counts (TVCs), coliform bacteria, and salmonella. The goal is to produce feed free of coliform bacteria and Salmonella sp.

From an enclosed storage and loading area, finished feed must be delivered to the farm by dedicated transport vehicles. Feed transport vehicles should be thoroughly decontaminated on a periodic basis and monitored routinely for Salmonella contamination.
In addition to a robust feed manufacturing and heat treatment process, feed additives such as organic acids or other antibacterial products in raw ingredients or finished feed have been effective in reducing total counts of enteric bacteria and the risk of recontamination. These antibacterial and/or feed acidifiers can, when properly applied, prevent the growth and proliferation of enteric pathogens and mold. These products have also been recommended to maintain clean silos, feed milling equipment, feed delivery vehicles and feed distribution equipment at the farm.

Rodent and Pest Control
Rodents are major vectors and reservoirs of S. typhimurium, S. enteritidis, and many other Salmonella species for poultry populations. Mice naturally infected with S. enteritidis can excrete at least 200,000 organisms per pellet.  Besides having a role in increasing the levels of contamination in the environment, rodents can effectively transmit the infection to other houses and farms. Therefore, it is critical to prevent rodent access to feed, water and shelter by:
1.    Building rodent-proof poultry houses (metal doors and concrete floors)
2.    Eliminating potential harborage areas inside and outside the poultry houses
3.    Disposing of dead birds and unused or spilled feed promptly and securely.
4.    Appropriate house management and sanitation
5.    Regular inspections and monitoring of rodent activity
6.    Rodent baiting and trapping

The control of insect vectors (particularly flies and beetles) through good management practices, and careful selection and use of pesticides is essential. Darkling beetles (Alphitobious diaperinus) have been found to carry over five different serotypes of Salmonella and shed S. typhimurium in their droppings for up to 28 days. Darkling beetles are one of the main vectors in the re-introduction of salmonellae to the chicken house after it has been cleaned and disinfected. In fact, it is known that beetles and flies can fly more than a mile, introducing Salmonellae into other farms in their path.

Other Farm, Domesticated or Wild Animals
All warm and cold-blooded animal species are potential carriers of Salmonella. For this reason, poultry houses should be constructed to exclude the entrance of wild animals and perching of birds inside and outside (roof, eaves). Feed spills should be cleaned up immediately to avoid attracting wildlife. Monitoring procedures have shown the presence of Salmonella in the droppings of rats, mice, raccoons, skunks, opossums and reptiles. Any other kind of farm animals and pets (dogs, cats, etc.) should be banned from the poultry farm. Experiences with salmonellae and Campylobacter jejuni (another human enteric pathogen getting increasing attention) have demonstrated the high risk of allowing cattle to graze in close proximity to the poultry farm and/or in-between chicken houses.

Water Sanitation and Management
Drinking water can be another source of Salmonella and enteropathogenic E.  coli. Studies of effluent from sewage treatment plants and the monitoring of individual wells and municipal water sources have shown the presence of Salmonella spp. Chlorination (3-5 ppm), and other methods of water sanitation are gaining popularity in the broiler industry as effective means of reducing exposure to pathogens and boosting flock performance.

Water pH  (< 6.5) can enhance the effectiveness of chlorine and other water sanitizing agents. Water acidification is showing encouraging results as a method of promoting healthy intestinal flora and suppressing the colonization by pathogenic organisms.
Water activity in the litter has a direct effect on the level of Salmonella in it.  Increased moisture levels promote the survival and transmission of Salmonellae. Water restriction programs and the use of closed drinking systems, along with proper ventilation, have resulted in reductions of moisture and levels of Salmonella in the poultry house environment.

Review and Updates
For all the above reasons an effective biosecurity program should be set and practiced as a multidisciplinary team effort. It is imperative to understand that, while the enforcement of a biosecurity program should be rigid, the program itself should never be “set in stone.” Constant review and updating are necessary for its success. Individuals should be encouraged to ask questions and offer suggestions for continuous improvement of the program.  Furthermore, employee and grower participation must be recognized and be part of the periodic performance evaluations.

House Cleanout and Disinfection
House cleanout and disinfection procedures are an integral part of the biosecurity program. These procedures are required between growing cycles to eliminate or reduce the concentration of Salmonellae and other pathogens that may infect subsequent flocks. Chicks are extremely susceptible to Salmonella infections after hatch and during the first days of life.
Likewise,  pullet flocks transferred from growing to laying facilities are highly susceptible to Salmonella infections. This is due to stress and changes in their normal gastrointestinal flora. As new flocks arrive at farms it is important that their environments be as clean as possible.

Bacteriological monitoring of new litter material has proven to be valuable in avoiding the introduction of Salmonellae and mold. Primary breeders prefer litter material that has been heat-treated and transported in clean and disinfected vehicles.

The first step is to plan a flock placement schedule that allows sufficient down time for all houses to be cleaned. A minimum period of four weeks for pullet houses and six weeks for laying houses is needed to do repairs and maintenance followed by thorough cleaning and disinfection.

Education and training of specialized crews are needed to develop a philosophy of “cleaning and disinfection of a food producing facility” instead of “a chicken house.” Attention to detail must be emphasized in order to avoid failures or having to repeat steps. The effectiveness of these procedures must be monitored routinely by testing schemes and the evaluation of CCPs.

Chicks may be exposed to Salmonella in the hatchery, either by exposure to infected hatch-mates or from environmental contamination. Essential components of a Salmonella control program in the hatchery are robust biosecurity and hygiene programs. A routine environmental monitoring program should be implemented to evaluate their effectiveness.

Interventions like fumigation of the hatchers during hatch may limit cross-exposure.

Single stage incubation provides a higher degree of biosecurity as it allows the segregation of hatching eggs and chicks sourced from flocks if these are found Salmonella positive during routine monitoring procedures.

Therefore, stringent biosecurity along with an effective traceability system greatly reduces the risk of lateral transmission during the hatching and chick servicing processes.

Aids to Complement the Biosecurity Program
The implementation of an effective integrated-biosecurity program that prevents the introduction and infections caused by enteric pathogens is the main tool to protect valuable breeding stock, contribute to customer satisfaction, and ensure the profitability of the primary breeder operations.

The effectiveness of this program is monitored routinely by testing schemes and the evaluation of CCPs. The combination of biosecurity practices and evaluation procedures are the main focus of our program.

Healthy intestinal flora has shown to protect chickens against colonization by Salmonellae and other pathogenic bacteria of the intestinal tract.

Unfortunately, the normal acquisition of flora is complicated by the fact that chicks are hatched and placed in clean environments. Consequently, chicks are not exposed to healthy intestinal flora that in nature would come mostly from their parents.

The use of defined and non-defined avian gut flora (competitive exclusion) has been shown to aid chicks in establishing a normal flora that protects them against Salmonella infections. Other bacteria such as Lactobacillus (probiotics) have been used to maintain a healthy intestinal flora and help flocks during periods of stress or after antibiotic treatments.

Evolving methods and products used to manipulate intestinal microflora are becoming increasingly important since growing public pressure against the use of antibiotics in food animals, and the ban of many of them have become a reality in many countries around the world. The uses of essential oils,  carbohydrates, herbs, or spices (prebiotics, natural substances or nutraceuticals, etc.) are being considered as potential alternatives to prevent colonization by enteric pathogens.

Immunization has been used strategically to protect at risk flocks and prevent vertical transmission. This method is not used to control host specific avian Salmonellae. Inactivated Salmonella vaccines formulated against specific serotypes (autogenous products) have shown benefits for breeders and their offspring. The induction of immunity in the hens against specific Salmonella serotypes prior to the onset of egg production helps to reduce of the risk of vertical transmission.

Also, field experiences suggest that maternal antibody can protect chicks against early exposure. A few live Salmonella vaccines (deletion mutants) have become commercially available to protect against specific Salmonella species by reducing the risk of colonization, persistence, and spread of pathogenic-field strains.

The use of any immunization method by a primary breeder company requires careful selection and planning to avoid interfering with routine microbiological and serological monitoring procedures.

A high degree of success has been achieved at reducing environmental shedding and egg transmission of Salmonella using antimicrobial treatment.

The effectiveness is dependent on two factors; selection of the most appropriate antimicrobial, dosage and length of treatment, and moving the treated flock to a clean house so that the flock is not re-exposed to environmental contamination. As the breeding program progresses to a nearly or completely salmonella-free status the use of interventions becomes infrequent and the strategy may be revised to incorporate depopulation of all Salmonella positive flocks.

Aids or interventions provide additional protection but they are not a “quick fix.” They cannot substitute for an effective integrated-biosecurity program.

The success and value of these complements depends largely on the biosecurity program’s ability to limit exposure.

As mentioned before, a comprehensive monitoring system for Salmonella is essential to determine the effectiveness of routine biosecurity and hygiene practices at many different points of the production system, to evaluate progress, and to define the status of flocks and their progeny.

Today, serology, cultures, and PCR assays are part of the Hazard Analysis of Critical Control Points (HACCP) approach used increasingly by the primary breeders and producers of poultry meat products. Samples for monitoring procedures must be routinely collected from the birds and their housing environments during the rearing and production phases, their progeny and hatchery environment, egg storage facilities, equipment and transport vehicles, feed and feed manufacturing environment, designated clean and dirty areas, facilities after cleaning and disinfection procedures, and all other potential inputs. Laboratory results then are circulated to appropriate managers in order to verify freedom from infection or take corrective actions as needed.

In closing, it is hoped that further developments aimed at increasing the effectiveness of current biosecurity and monitoring procedures, along with the evolution and/or discovery of novel-suitable intervention strategies will result in further advances in the health status of breeding and broiler/layer flocks leading to increased safety of broiler meat and egg products. We consider food safety a top priority and will continue to support the industry’s efforts by using the best methods available to ensure the production and delivery of healthy-safe breeding stock.