The term disease, according to the online Merriam-Webster Dictionary, means: “a condition of the living animal or plant body, or one of its parts, that impairs normal functioning and is typically manifested by distinguishing signs and symptoms”.
While infectious agents are generally considered the cause of disease, it can be caused by management practices. Management is defined by the same dictionary as: “The act or art of managing: the conducting or supervising of something (as a business)”.
In the case of pullets and layers, management means feeding, lighting, watering, ventilating, beak trimming, vaccinating, medicating, monitoring, catching, moving, and so on. Failure to properly implement any of these aspects of management can result in disease.
There are several management factors that can contribute to the problem of cannibalism (vent trauma and peckouts), however beak trimming is probably the most important.
Poor trimming, ie leaving longer than normal beaks, gives birds a tool to use to exhibit aggression against their penmates. Certain strains of layers or pullets that are to be placed into high light intensity situations, need a more severe beak trim than pullets placed into light controlled facilities.
This is a real challenge when there is a requirement for beak trimming no later than 10 days. To achieve a beak that is 4-6 mm from the nostril to the end in a mature layer, the beak needs to be trimmed to 1 mm from the nostril and cauterized 2-2.5 seconds with a relatively cool, sharp blade.
In some cases, 10 day beak trimming has resulted in over 2% mortality per week in brown-egg, organic layer flocks in curtain-sided houses. As this is not satisfactory, the grower may opt to beak trim at 7-8 weeks of age, however, this will result in the loss of audit points or failure to satisfy organic standards for beak trimming after 10 days.
The use of higher light intensity than necessary has also lead to increased cannibalism, feather pulling, and nervous behaviour (hysteria). High light intensity allows flockmates to visualize the everted oviduct during oviposition and pecking occurs. Additionally, allowing outside light to flood houses unimpeded through windows or curtains has lead to peckout mortality.
In cage-free housing, a change in nest usage and increased competition for nest space can occur due to birds avoiding highly lit nests. Using the appropriate wattage and spacing helps to reduce cannibalism. Using light screens over curtain or window openings will help to reduce problems.
Space allotment can play a role in the incidence and severity of cannibalism. Not giving enough floor, nest, water, or feeder space has been found to lead to nervous flocks and birds that are aggressive. Recent investigations of peckouts in cage-free flocks placed in former broiler breeder houses showed that the nest space given was too little for egg-type birds and peckout mortality became a problem.
The importance of maintaining normal humidity and ventilation during growing to minimize the number of sporulated oocysts is demonstrated by a case of coccidiosis in 17-day-old pullets.
A Cocci-Vac vaccinated flock of caged pullets was poorly ventilated during a winter growout. This resulted in the cage papers, which had been left in the cages longer than usual to 14 days of age to allow better cycling of the vaccinal organisms, to become wetter than normal. Consequently, there was an increase in the number of sporulated oocysts, and 5% of the chcikes were lost to cecal coccidiosis.
Proper ventilation, resulting in humidity levels of 40-60%, should be maintained. Removing cage papers at the normal 10 days, and adding paper or plastic plates in flocks that have been vaccinated with coccidia vaccine, will reduce this sort of problem.
The mismanagement of chain feeding systems in cage houses can lead to problems with calcium depletion and soft bones in layers, especially on the return-side of the system.
Not running the feeder long enough to fully make a cycle around the tier can be one problem. A second, is using a slow speed chain feeder giving the feed-side birds a chance to pick out and eat the large particle calcium as the feeder runs, and depriving the return-side birds. Lowered egg production due to lower body weights of the return-side birds has also been a problem.
The age at which pullets are moved to the layer house can affect the incidence and severity of Escherichia coli-related problems.
The later that pullets are moved to the layer house, particularly in the case of multi-age complexes, the greater the problem related to the amount of time the birds have to mount an immune response to disease agents present on the layer farm, prior to placing all their energy into egg production.
Some producers backfill older layers into flocks just prior to molt to fill cages left less than full due to mortality during the first cycle. This practice can lead to increased E. coli problems due to the introduction of different viral and bacteria flora, as well as the stress of adding new members to the cage. Additionally, the immune systems of these older birds are not as capable of resisting bacterial disease, which increases the exposure of other birds.
Poor water quality management can lead to very severe losses due to colibacillosis. Using contaminated water sources can lead to more E. coli infections, but this can be prevented.
For example, a producer with contaminated wells prevented problems by adding iodine disinfectant to the water. However, this must be done properly. A case has been reported where a worker filled an empty iodine disinfectant barrel with water, and the resulting solution was used as if it was fully potent disinfectant A loss of 6% of the younger layer flock ensued in two weeks.
A lack of attention, or simple adjustments, to management practices can make a significant difference. There is a case recorded of hysteric pullets that led to gangrenous dermatitis due to Staphylococcus spp, and Clostridia spp infections of the scratch wounds. This hysteria was caused by manure scrapers under the cages that were running too fast, and exciting the birds every time they ran. The problem was solved by using a different gear to slow the scrpaters.
Ammonia induced corneal ulcers
Numerous cases of ammonia induced corneal ulcers have occurred due to mismanagement of ventilation systems during the winter. This mismanagement can lead to high humidity levels, increased manure or litter moisture, and greater ammonia emissions.
Managing ventilation is not simply down to fan running time. In one recorded case, ammonia and humidity was not properly removed by the ventilation system because of poorly constructed fan housing in the front third of the pullet house. This housing allowed air to enter around the perimeter of the housing, bypassing the normal air inlets, with the result that house was not ventilated properly.
Paying attention to the details of management will help avoid many disease related problems. Keeping FLAWS – Feed, Lights, Air, Water, Space – and other management practices in mind when servicing and trouble-shooting flocks will help to prevent or solve many of these problems.