Summer Diseases in Poultry
According to the India Times, A hotter than normal summer is expected in 2023 with temperatures likely to reach 2-3 degree celsius above normal in some parts of Indo-Gangetic plains and eastern India during the last week of March, the India. In this summer season, as the temperature increases, poultry suffers from the condition called heat stress, also known as summer stress. This is a condition is due to imbalance between heat generation and heat loss in the body. This condition not only brings poor performance in birds but is also responsible for huge economic losses in terms of poor growth, lowered production, and higher mortality. The poultry farmers have to take all the precautionary measures to handle the heat problem to save the birds from heat catastrophe.
What is heat stress?
When the Birds are ‘heat stressed’ they have difficulty in achieving a balance between body heat production and body heat loss. This can occur at all ages and in all types of poultry. Poultry is most comfortable in an environmental temperature around 22-28°C (known as their thermoneutral zone). In other words, Heat stress is the result of unsuccessful thermoregulation in the animals, as they absorb or produce a higher quantity of heat than they can lose. Exposure of birds to high environmental temperature generates behavioral, physiological and immunological responses, which impose detrimental consequences to their productivity (fig1).
Why the poultry are more prone to heat stress?
The poultry birds are susceptible to high environmental temperature due to their physiological buildup such as absence of sweat glands making it impossible for them to dissipate heat, their full body of feathers, their higher body temperature, and the fatty nature of the birds. The heat or summer stress not only brings lowered performance in poultry but also leads to immunosuppression issues, which can result in disease outbreaks and cause heavy mortality. In this, males are found to be more prone to heat stress than females. Therefore, breeders have to take extra care in summer to prevent fertility problems in breeder males.
What are the contributory Factors of Heat stress?
Environmental factors such as sunlight, thermal irradiation, air temperature, humidity, When the environmental temperature is above the thermoneutral zone, the animals activate thermoregulation mechanisms to lose heat through behavioral, biochemical, and physiological changes and responses.
- At temperature above 35o C bird is likely to experience heat stress as having a high body temperature of 41°C and absence of sweat glands makes it difficult for them to dissipate their heat to surrounding.
- Stocking density, more birds in the shed increase heat and humidity.
- Bird related factors such as body weight, feather coverage and distribution, dehydration status, metabolic rate, and thermoregulatory mechanisms.
- Heat stress can be classified into two main categories, acute and chronic. Acute heat stress refers to a short and fast increase in environmental temperature (a few hours), whereas under chronic heat stress the high temperatures persist for more extended periods (several days), the former acute condition there will be more mortality.
What are the signs of heat stress in poultry?
- Spreading the wings away from the body.
- Increased respiratory rate.
- Squatting/low to ground.
- Reduced feeding.
- Increased drinking/resting.
- Cause pale wattles and comb,
- Lethargy, limp, unsteady gait, or unconscious.
- Heat stress causes acid-base disequilibrium, or the inability to cool the body to maintain normal body temperature.
Behavioural, neuroendocrinal, and physiological changes are observed in birds during heat stress. Behavioural changes can include decreased feed intake, increased water intake, panting, less walking, and elevated wings. Physiological changes include oxidative stress, acid-base imbalance, and respiratory alkalosis. Internally the bird may experience decreased protein digestion and absorption, increased metabolic disorders, Increased chances of disease prevalence, and fertility issues. Production challenges can include reduced feed intake, poor feed conversion ratio, reduced body weight, impaired meat, and egg quality, and, increased mortality.
Effect of heat on food safety
There is an increasing evidence to demonstrate that heat stress can have a significant deleterious effect on food safety through a variety of potential mechanisms.
- The negative effects of heat stress on broilers and laying hens range from reduced growth and egg production to decreased poultry and egg quality and safety.
- Chronic heat exposure negatively affects fat deposition and meat quality in broilers.
- Productivity of laying hens flocks also be affected by a multitude of factors, which is probably one of the most commonly occurring challenges in many production systems.
- Decreased feed intake is very likely the starting point of most detrimental effects of heat stress on production, leading to decreased body weight, feed efficiency, egg production and quality.
- Heat stress leads to reduced dietary digestibility, and decreased plasma protein and calcium levels.
- Heat stress during the growth period of broilers has been associated with undesirable meat characteristics and quality loss.
- Transportation of broilers from farms to processing facilities under high temperature conditions have also been shown to cause meat quality losses.
- In laying hens, heat stress has been shown to negatively affect egg production and quality.
- During heat stress, foodborne pathogens, such as Salmonellaand Campylobacter colonize and disseminate along the human food chain causing a major public health and economic concern in poultry and egg production.
Why disease incidence is more in summer?
- Alters antibody and cell-mediated immune responses, thereby immunosuppressing effect and increasing susceptibility to pathogens.
- Vaccine failures are common in summer seson.
- Summer stress also results in immuno-deficiency and disease outbreaks in poultry.
- Heat stress in summer leads to reduced feed consumption, lower body weight gain, high feed conversion ratio (FCR) and dehydration.
- It also causes a variety of changes in gastrointestinal tract including alteration of the protective microbiota as well as decreased integrity of the intestinal epithelium increasing enteric infections such as Necrotic Enteritis.
- An increase in energy demands, increased culls and high mortality are observed due to heat stress.
What are the common poultry diseases during summer?
The most common infections occur are from Bacterial, Viral, Fungal and Parasitic. Newcastle and bronchitis vaccine reactions can occur in birds hyperventilating because of heat stress. Vaccination failure is mainly because of Stress like extreme temperature or relative humidity causing immunosuppression.
Summer favours increase in vector population such as flies, beetles and mosquitos and these act either as intermediate hosts or carriers of infectious agents including Newcastle disease and Avian Influenza. House flies are considered intermediate hosts for tapeworms and may transmit ascarids to caged birds. Flies mechanically carry ascarid and other nematode eggs on their feet from manure to pens, feed, and water and rats in the shed transmits salmonella and tapeworms.
Heat stress is one of the most important environmental stressors challenging poultry production worldwide. There is more heat experienced in recent years due to climate change and global warming. The negative effects of heat stress on breeders, broilers and laying hens range from reduced growth and egg production to decreased poultry and egg quality and safety. However, a major concern should be the negative impact of heat stress on poultry welfare.
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