Aquaculture Articles on Poultry Health
The condition of fatty liver in poultry has been observed for quite some time. While it is true that an alteration in liver function can lead to a build-up of fat in the liver, many cases of fatty liver in laying hens can be traced to an imbalance in nutrient intake. Low protein, high energy diets and those in which there is an amino acid imbalance or deficiency can be major contributors to a fatty liver condition in layers. It is known that diets low in lipotrophic factors such as choline, methionine and vitamin B12 can result in fatty infiltration of the liver.
Causes and Prevention of Wet Litter
Wet litter can be caused by either extrinsic (environmentally related) factors or due to intrinsic flock factors involving excessive excretion of water.
Moisture content of litter exceeding 35% is deleterious and may lead to the following conditions: -
• Dermatitis of the foot pads resulting in pododermatitis which is reflected in poor growth rate in broilers and low fertility in breeder flocks.
• Wet litter contributes to folliculitis (inflammation of the feather follicles) which stimulates gangrenous dermatitis and is responsible for downgrading at processing or rejection by consumers.
• Oocysts of Eimeria spp. require moisture levels in excess of 25% to mature and wet litter is often associated with outbreaks of coccidiosis.
• Necrotic enteritis occurs frequently in houses with areas of wet litter due to the high level of Clostridium perfringens which occurs in the vegetative (infectious) form.
• Damp litter may contribute to proliferation of toxic fungi.
• The bacterial flora of damp litter favors the production of ammonia. If levels exceed 50-ppm, keratitis (erosion of the cornea of the eye) and respiratory stress will occur.
Causes Of Wet Litter
• Ingress of rain
This problem is easy to recognize. Ventilation openings should be closed with shutters or watertight curtains. Houses located in areas subject to seasonal monsoon rains, typhoons or cyclones should be designed to withstand excessive wind and rain. Failure to activate curtains or shutters during rain is a management deficiency.
• Excessive Condensation on the underside of the roof
Under cold ambient temperature, uninsulated houses develop condensation on the underside of the roof sheeting, which drips onto litter. Appropriate levels of ventilation and the installation of roof insulation are required to correct this problem.
• Leaking Waterers and Piping
The causes of leakage from suspended bell drinkers and nipple systems should be investigated, followed by appropriate corrective action. This may involve installation of a pressure regulator or filters to prevent particulate matter which clogs valves from entering water lines. Non-ballasted drinkers, especially when suspended at an incorrect height, will spill water causing wet patches beneath drinker lines. Flooding will occur if rodents gnaw plastic water lines.
Excretion of water may occur in the form of urine (diuresis) or from the digestive tract (diarrhea). It is important to establish whether excessive release of fluid from the cloaca (wet droppings) is from the urinary or the digestive tract.
Infection of the intestinal tract will result in diarrhea. The causes include:
- Coccidiosis. This infection can be diagnosed by examination of intestines of sacrificed birds showing ruffled plumage and palor. Microscopic examination of mucosal scrapings confirms the diagnosis. Administration of appropriate therapy (sulpha drugs or amprolium) will restore normal function.
- Bacterial Infections will result in enteritis. Microscopic and microbiological examination of intestines from affected sacrificed birds are required to establish the diagnosis. Appropriate antibiotics (tetracycline, neomycin, zinc bacitracin or ampicillin should be administered in accordance with statutory regulations, manufacturer’s recommendations and the principles of prudent therapy.
- Viral infections including reovirus and other enteric viral agents can result in diarrhea especially in young flocks. This may last for a few days to a week. Diagnosis is based on electron microscopy of mucosal scrapings and feces, histological examination of intestinal tissue and attempts at viral isolation. All these procedures require a specialized laboratory. There are no specific treatments for viral infections other than supportive therapy comprising electrolyte supplements and raising the brooding temperature.
- Malabsorption of complex carbohydrates. Non-starch polysaccharides contained in wheat, barley, and some indigenous materials such as cassava cannot be completely digested in the anterior intestinal tract, resulting in digestive malfunction, bacterial degradation and diarrhea. Substitution of maize for alternative cereals and using high quality soybean meal in place of potentially toxic vegetable proteins should be considered. The digestibility of wheat, barley and unconventional carbohydrate sources can be improved by supplementing diets with specific enzyme combinations which are commercially available.
- Mycotoxins including aflatoxin and fusariotoxins are responsible for diarrhea. Analysis of feed will confirm the presence of these toxins. Appropriate corrective action involves substitution of non-contaminated ingredients or supplementing diets with an effective mycotoxin binder.
- Feeds containing rancid fat due to prolonged storage at high temperature will result in diarrhea. Incorporation of non-stabilized fat, byproduct meal or rice bran in tropical countries is a frequent cause of wet droppings, pasty vents and other deleterious effects including encephalomalacia, immuno suppression and low growth rate.
Birds will excrete excessive quantities of water at high ambient temperature. This is a normal result of increased water intake. High water consumption is a physiological response which enables the bird to dissipate body heat by evaporative cooling through the respiratory tract. Ingestion of cold water serves as a heat sink in the digestive tract, lowering core body temperature.
- Excessive salt or sodium or chloride in the diet will result in excessive water intake and diuresis. Improper levels of salt may be the result of incorrect formulation, defective mixing or accidental contamination of diets. High levels of salt may occur inadvertently through incorporating batches of fishmeal or carcass meal with a high sodium chloride content. Occurrence of diuresis or wet droppings following a change in diet or purchase of feed from a new source should be investigated, with appropriate analyses. Magnesium contamination of limestone in layer and breeder diets may also result in diuresis.
- Chemical and mineral impurities in water including sodium and magnesium may result in diuresis. Appropriate analysis of water will confirm the cause of diuresis which is usually a chronic problem in the flock.
- Mycotoxins including ochratoxins damage the kidney and will result in excessive excretion of water. The condition can be diagnosed by demonstrating the specific mycotoxin in feed associated with microscopic examination of kidneys of affected birds.
- Flocks infected with a number of nephropathogenic (affinity for the kidney) viruses may show diuresis during the acute and recovery phases of infection. Diuresis is observed with acute infectious bursal disease, avian nephrosis virus and nephropathogenic strains of infectious bronchitis virus.
- Replacement broiler breeder pullets subjected to skip-a-day feeding will show diuresis as a result of excessive water intake on non-feed days. Mature hens on post-peak restriction often demonstrate excessive water intake with resultant wet droppings. It is often necessary to implement a water restriction program, subject to the breeder’s recommendations regarding feed and water intake. It is inadvisable to implement a water restriction program if the flock is subjected to an ambient temperature above 30°C.