Maintaining the health of laying hens: a practical approach by BurleighDodds

Maintaining the health of laying hens: a practical approach Richard M. Fulton, Michigan State University, USA 1 Introduction 2 Biosecurity measures: separation 3 Other biosecurity measures 4 Disease identification and detection 5 Vaccination of poultry 6 Common diseases of egg-laying chickens: respiratory diseases 7 Common diseases of egg-laying chickens: nervous system diseases 8 Common diseases of egg-laying chickens: intestinal system diseases 9 Common diseases of egg-laying chickens: skeletal system, urogenital system and unclassified diseases 10 Where to look for further information 11 References

1 Introduction No treatise on maintaining the health of any poultry, including egg-laying hens, can be written without discussing biosecurity, which is the protection of the birds from agents that may cause disease. Biosecurity also prevents the spread of disease-causing agents such as bacteria, viruses and parasites from one group of birds to another. Biosecurity is a way of life that must be adopted and practised by everyone who comes in contact with poultry. Although there are many complex strategies to maintain biosecurity, these strategies can be classified as •• •• •• •• ••

separation people traffic control equipment and vehicles air, feed and water

Maintaining the health of laying hens: a practical approach

By providing proper biosecurity, the most common mechanisms of disease spread can be prevented and controlled. This chapter reviews the range of biosecurity measures required to maintain the health of laying hens. It also reviews disease identification and detection, including the identification of specific diseases and vaccination regimes for prevention or treatment.

2 Biosecurity measures: separation Separation means keeping the birds protected and separate from each other and sorted by age. This is especially important for chickens that are yet to attain the egg-producing age (pullets) and for egg-laying hens. Separation, as for other elements of biosecurity, is best applied prior to building bird housing facilities. Young chickens are typically more susceptible to disease than old chickens. When constructing a farm that will have both pullets and laying hens, the pullet facilities should be built upwind of the layer farm. Since some agents can be borne on the wind, a minimum distance of 0.5 miles (0.8 km) is recommended. The more the distance between the facilities, the better. Separation is also maintained by providing a break or buffer zone in facilities where workers must change their footwear, outer clothing and head covering (hair nets or hats) before entering the compartment where the birds are housed. Ideally, it is a seperate building where workers arrive to work on the farm. The workers enter the dirty side (the section just inside the exterior opening), remove their clothing and shoes, take a shower, put on the provided clothing, and enter farm or bird room if shower facility is attached to bird-raising facility. On the clean side (the section adjacent to the entrance of the bird room), workers will don clothing, head coverings and footwear provided by the farm before entering the farm. A separate facility at the edge of the farm is best. At a minimum, this can be accomplished with an anteroom constructed just inside of an exterior door but before the area where the birds are kept. An anteroom placed prior to the bird room could be divided into a ‘dirty’ and ‘clean’ side. A real or imaginary break between these two sides may be delineated by a painted red line or by benches that stretch across the entire anteroom. People enter the anteroom; remove covering garments (hats, coats, jackets, etc.); step or swivel across the red line or bench; and put on building-specific coveralls, boots and head coverings on the ‘clean’ side of the anteroom. It is best if workers wash their hands before entering the bird room. Ideally, coveralls, hats and footwear should be designated for use in only one facility. Colour coding of coveralls, footwear and head cover attracts the immediate attention of observers, who can report this infraction to their superiors if items of the wrong colour are observed in areas other than those assigned. Separation of birds of different ages is commonly referred to in the poultry industry as practising ‘all in, all out’ poultry management. For broiler chickens, one building or all buildings on a farm are stocked with chickens of the same age. When those chickens reach the market age, the entire building or the entire farm has to be processed before adding extra birds. ‘All in, all out’ management prevents disease from spreading between flocks, since the birds are not maintained in the building or on the farm continuously, and the buildings can be cleaned and disinfected prior to stocking with new chickens. Providing ‘down time’ when there is no poultry on a farm will help reduce the load of some diseasecausing agents or eliminate them altogether. Unfortunately, because of scalability, land

Maintaining the health of laying hens: a practical approach 3

availability and costs of construction, many commercial egg layer farms house chickens of multiple ages. Birds of each individual age are typically housed in a single unit, but one often finds a conveyor that passes through multiple houses to transport the eggs to the central egg-processing building. In addition, the bird houses on some layer farms are constructed in close proximity to each other. Often, the air exhaust vents of one building are located directly across from the air intake vents of another building. Separation from pets and pests including mice, rats, raccoons, woodchucks, possums and wild birds is also important to prevent the spread of disease. Cats and rats are known to harbour in their mouth Pasteurella multocida, the bacteria causing fowl cholera. Mycoplasma gallisepticum has been found in wild birds and is thought to have caused problems in turkeys (Ferguson, 2003). Bird facilities and their surroundings must, therefore, be constructed in such a way that prevents pests from being attracted to the buildings or from entering them. In addition, wild-bird screening must be in place on all openings of the buildings. The common rule of thumb for pest exclusion is that if a pest can get its head through an opening, it can get its entire body through the opening. At a minimum, a 10-foot (3 metre) zone surrounding the bird facility should be kept free of grass and weeds. This provides a buffer zone to prevent mice from entering the facility. Tall weeds and/or grass close to the buildings act as a hiding place for mice, allowing them to evade aerial predators. It also provides food source, including insects and weed seeds, for mice. Piles of unused equipment or trash should be kept at least 100 feet (30 metre) away from the buildings, since rats like to live in piles of rubbish and will travel 100 feet for food and water. Rodent bait stations should be placed every 25 feet (7.6 metres) along the exterior foundations as well as immediately beside any exterior openings on the interior of buildings. The type of rodent bait that is used should be changed every 3 months. Since most rodents have continuously growing incisor teeth, they must gnaw on things. A chew bait, therefore, is often a better choice than a seed bait or paste.

3 Other biosecurity measures People must always be mindful of biosecurity and put it into practice. At first, biosecurity may not be natural behaviour, but with time, practice and a well-designed facility, it can become second nature. Only those people who have a definite need to visit the bird facilities should be allowed to do so. A visitor logbook should be maintained, where the names of the persons, the company they represent, the purpose for the visit, the areas that are visited, and the date and time they enter and leave the facility should all be recorded. A person should not be allowed into a poultry facility unless a period of at least 48 hours has elapsed since they last visited other poultry facilities. Outside contractors should be encouraged to come to the facility on Mondays since this will allow at least 48 hours between poultry visits. Ideally, visitors coming from other countries should allow at least seven days between contact with poultry and visiting poultry facilities. People are known to spread disease from one group of poultry to another. They can carry disease agents on their clothing, shoes, hands and headwear. Most, if not all, poultry companies require their workers to sign a form stating that they will not own any poultry, visit anybody who owns poultry, visit cock fights, visit pet stores or poultry exhibits and hunt waterfowl or upland game birds. If hunting is allowed, a period of 48–72 hours is required before they can return to work. They will also be asked to declare whether or not they live with anybody