484
A. Soliman and A. M. Safwat
losses in electrolytes, sodium, potassium and bicarbonate. Some organs, such as the
brain and circulatory system, are also affected and the burden on the heart and blood
vessels increases. The rate of urinary incontinence is the result of water consumption.
In the end, the immunity of birds is significantly reduced, especially the reduction of
immunoglobulin in the blood, and the herds become more susceptible to diseases. All
previous manifestations of high temperature affect the herds produced in the form of
symptoms such as bird swings with peripheral spasms, low body weight, increased
predation disease, decreased egg production, decreased cortex quality, decreased
fertility and poor semen quality, and finally in severe cases to death.
Many studies have shown the possibility of adapting birds to the conditions of heat
stress and their tolerance to this burden and low mortality if exposed early in the age
to high temperature, and this adaptation is reflected in increased rates of fatigue and
low body weight and the lack of water lost by evaporation, high on several factors,
including: type of strain, average body weight, quantity of drinking water available
and quantity of production.
2.4 Immune Response
The immune system functions can be broadly classified into: (i) innate immunity
and (ii) adaptive immunity. Innate immunity is the germ line encoded, non-specific,
preliminary line of defense against the invading pathogens. The first entry of the
pathogens is prevented at body’s entry site through antimicrobial components in
mucosa, sweat, tears, saliva, etc. Heat stress directly or indirectly favours disease
occurrence in animal host. Directly, high temperature favours the survival of organisms outside the host for a long time. Indirectly, chronic heat stress causes immune
suppression in birds and makes them susceptible to diseases. Heat stress reduces
the relative weights of lymphoid organs like spleen, thymus and cloacal bursa. This
might be due to glucocorticoid induced lympholysis and redistribution of lymphocytes from systemic circulation to other organs NK cells are important components
of the innate immune system present in systemic circulation and also in lymphoid
organs like lymph nodes, spleen and bone marrow. They are involved in destruction
of tumour cells and infectious agents like bacteria, fungi and viruses. Chronic heat
stress reduced the splenic NK cell cytotoxic functions. The inhibition may be due to
increased glucocorticoid influence in the immune cell [4].
Cytokine interactions are responsible for altered immune functions during heat
stress. Stress induced glucocorticoids act to inhibit the pro-inflammatory cytokines,
which are required to initiate an innate immune response through inhibition pathway.
Heat stress leads to activation of hypothalamic-pituitary adrenal axis and ultimately the release of glucocorticoids. Glucocorticoids, in normal pulsatile release,
enhance the pro-inflammatory cytokine release. However, chronic rise in glucocorticoid levels is inhibitory to majority of immune cytokines. The stress related immune
responses in poultry species revealed that acute stress is beneficial to the bird as it the
immune system. On the other hand, chronic stress shifts the T helper cell response
A. Soliman and A. M. Safwat
losses in electrolytes, sodium, potassium and bicarbonate. Some organs, such as the
brain and circulatory system, are also affected and the burden on the heart and blood
vessels increases. The rate of urinary incontinence is the result of water consumption.
In the end, the immunity of birds is significantly reduced, especially the reduction of
immunoglobulin in the blood, and the herds become more susceptible to diseases. All
previous manifestations of high temperature affect the herds produced in the form of
symptoms such as bird swings with peripheral spasms, low body weight, increased
predation disease, decreased egg production, decreased cortex quality, decreased
fertility and poor semen quality, and finally in severe cases to death.
Many studies have shown the possibility of adapting birds to the conditions of heat
stress and their tolerance to this burden and low mortality if exposed early in the age
to high temperature, and this adaptation is reflected in increased rates of fatigue and
low body weight and the lack of water lost by evaporation, high on several factors,
including: type of strain, average body weight, quantity of drinking water available
and quantity of production.
2.4 Immune Response
The immune system functions can be broadly classified into: (i) innate immunity
and (ii) adaptive immunity. Innate immunity is the germ line encoded, non-specific,
preliminary line of defense against the invading pathogens. The first entry of the
pathogens is prevented at body’s entry site through antimicrobial components in
mucosa, sweat, tears, saliva, etc. Heat stress directly or indirectly favours disease
occurrence in animal host. Directly, high temperature favours the survival of organisms outside the host for a long time. Indirectly, chronic heat stress causes immune
suppression in birds and makes them susceptible to diseases. Heat stress reduces
the relative weights of lymphoid organs like spleen, thymus and cloacal bursa. This
might be due to glucocorticoid induced lympholysis and redistribution of lymphocytes from systemic circulation to other organs NK cells are important components
of the innate immune system present in systemic circulation and also in lymphoid
organs like lymph nodes, spleen and bone marrow. They are involved in destruction
of tumour cells and infectious agents like bacteria, fungi and viruses. Chronic heat
stress reduced the splenic NK cell cytotoxic functions. The inhibition may be due to
increased glucocorticoid influence in the immune cell [4].
Cytokine interactions are responsible for altered immune functions during heat
stress. Stress induced glucocorticoids act to inhibit the pro-inflammatory cytokines,
which are required to initiate an innate immune response through inhibition pathway.
Heat stress leads to activation of hypothalamic-pituitary adrenal axis and ultimately the release of glucocorticoids. Glucocorticoids, in normal pulsatile release,
enhance the pro-inflammatory cytokine release. However, chronic rise in glucocorticoid levels is inhibitory to majority of immune cytokines. The stress related immune
responses in poultry species revealed that acute stress is beneficial to the bird as it the
immune system. On the other hand, chronic stress shifts the T helper cell response