During the rainy season, humidity is likely to increase resulting to damp litter or feeds providing favourable conditions for pathogens.
As the cold rainy season sets in, your poultry production and the general well-being of your chicken will certainly be affected.
You will experience sudden shift in chicken behaviour for them to adjust to the weather changes.
Your birds will tend to huddle in groups or increase their level of feed consumption or reduce water intake. These are some of the mechanisms birds employ to generate heat and keep warm.
In most cases when the cold conditions are extreme, the birds become stressed and this affects their production and ability to withstand diseases through immunosuppression leading to reduction in egg production.
Further, the cold and wet seasons we are currently experiencing come with various pathogenic and parasitic diseases that may cause heavy losses.
However, the extent of disease occurrence, morbidity and mortality rates during this season is majorly a factor of the type of management practices and vaccination status of your flock.
The age of birds also plays a role as different age groups have unique requirements and abilities to survive the weather changes. Birds under two months of age (normally at the on-set of a rapid growth phase) and those over six months of age (in the process of becoming sexually mature) are more susceptible to infectious diseases.
Common disease symptoms during the season include respiratory distress, nervousness, diarrhoea, loss of appetite, ruffled feathers, swollen face and prostration.
These observable symptoms may be associated with several diseases making it difficult to carry out a differential diagnosis to help identify the disease your flock is suffering from. Majority of poultry farmers identify these symptoms with New Castle Disease.
However, this viral disease is more prevalent during the hot, dry and windy periods, which encourage the airborne spread of the virus, in addition to the hot climatic conditions that lead to stress and predisposes the birds to the disease.
The following diseases are prevalent during the rainy season:
Infectious Bursal Disease (Gumboro):
A viral infection that mostly affects immature birds aged between three and 18 weeks targeting the bursal component of the immune system resulting in immunosuppression and susceptibility to secondary infections.
Chickens may exhibit severe prostration, incoordination, watery diarrhoea, soiled vent feathers, vent picking, and inflammation of the cloaca.
Highly contagious with flock morbidity of typically 100 per cent, and mortality can range from 5–20 per cent. Unfortunately, there is no effective treatment for this disease, therefore, depopulation of infected flocks and rigorous disinfection of contaminated farms is advisable.
Usually, the level of maternal immunity and vaccination reduces susceptibility to this infection during the rainy season.
Fowl pox (non-zoonotic):
Occurrence is highly dependent on the breeding time of mosquitos or blood-sucking insects, which coincides with the rains.
The insects play a major role as vectors in transmission of the pox virus. The disease may occur at any age and is highly contagious attacking the skin and surface of the upper alimentary and respiratory tract leading to formation of wounds that progress to thick scabs.
Secondary infection of the pox results in birds being weak and emaciated due to loss of appetite, difficulty in swallowing and breathing, swollen eyelids leading to closure of one or both eyes and soiled feathers.
The infection has no treatment but it is possible to vaccinate to stop the outbreak.
Vaccinate healthy birds at the age of nine weeks, and this is done once as it provides lifetime immunity. Eliminate standing water and all mosquito habitats to control mosquitoes.
Isolate or cull infected birds to remove the source of the virus.
It strikes birds older than six weeks. In acute outbreaks, the first warning sign is usually sudden death of birds that initially appeared healthy.
In chronic cases, affected birds exhibit laboured breathing, diarrhoea (wet grey, yellow or green droppings), loss of appetite, ruffled feathers, drooped wings and tail feathers and the tendency of bird to sit quietly with their heads tucked in and eyes partly closed.
Depending on the localisation of the disease, it may result in lameness and swelling of legs or wing joints or result in twisted neck, swelling around the eyes and discharge from beak or nostril. Symptoms of the chronic form may be confused with fowl typhoid.
E-coli and Salmonella:
They occur as secondary infections following immunosuppression and poor sanitation resulting from wet conditions.
The common symptoms include breathing difficulties, appetite loss, depression, infection of the umbilical stump (omphalitis) and low growth rates. Management of this disease can be achieved by oral administration of broad-spectrum antibiotic and general sanitation management.
During the cold season, the humidity is likely to increase resulting to damp litter or feeds which provide favourable environment for fungus (Aspergillosis) to flourish in which the birds breathe in the spores, which grow into visible lesions as green and yellow nodules that completely fill the lungs causing a lot of respiratory discomfort.
High incidences of diseases under free-range during the cold season are due to uncontrolled exposure of birds to environmental influence, absence of housing, lack of routine vaccination and adequate feeding while in the case of intensification, the degree of stocking density and inadequate ventilation highly promotes the spread rate of the diseases.
Cold season management tips
During the cold period, birds increase their level of feed intake to generate heat and stay warm.
However, for a farmer, increasing the level of feed provision raises the cost of production besides wastage of nutrients that are not needed for heat generation.
To reduce costs and avoid wastage, energy rich sources like oil/fat should be added to the diet or level of other nutrients may be reduced keeping the energy at same level.
In free-range system, provide supplementary feeding to the birds to meet their nutrient deficit. Consider providing your birds with warm water periodically during this rainy season to encourage consumption and help them keep warm without using up energy reserved in the process.
With the rain, birds may encounter standing water (mostly in free-range) and end-up drinking from the ground leading to parasitic infestation from intestinal worms.
De-wormers administered after every three months help in management of worms, but you should remember the product withdrawal period as specified by the manufacturer.
Poultry house should be designed in such a way that it provides all the comfort required by birds during cold season while considering ventilation as well.
In regions where it rains heavily, the floor should be raised with a generous roof overhang, particularly over the entrance.
The raised floor can be a solid platform of earth to prevent floods. Orientation of a building with respect to wind and sun consequently influence temperature, and light on different external surfaces.
With better management, your flock will remain healthy and productive throughout the cold season.
Sophie Miyumo, Department of Animal Sciences, Egerton University.