PHYSIO-PATHOLOGY OF SUMMER STRESS IN LAYERS
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Date
1989
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AAU, Anand
Abstract
The present study was made on layer birds kept at AICRP on poultry, Gujarat Agricultural University, Anand Campus, Anand. The study was conducted during extreme period of summer heat. For comparison, base level data were obtained by conducting similar study during comfortable environmental temperature of winter season .The experimental birds were divided into five groups with different housing and managemental systems. Samples like blood, serum, plasma and tissues were collected during morning and after-noon from each group and used for the study. Study was also made on natural cases of heat stroke and FLHS. Relationship of heat stress with incidence of FLHS as well as effect of housing system were also analysed. Concentration, of thyroid hormone in plasma was significantly decreased during summer season. Serum cholesterol level decreased during summer season as well as in after-noon than morning serum samples, suggesting lowered functioning of liver under heat stress. Relative weight of adrenal gland was increased during summer season, indicating increased activity of adrenal gland. Short term increase in temperature caused increase in the glucose level while, birds exposed for long period of high cyclic temperature (summer season) caused decrease in level of blood glucose. Activities of AXF and ALT increased during summer season. Thesealso increased in after-noon samples during summer season. The level of AKP was significantly higher in cage birds than deep litter birds during summer season, suggesting more stress of caging. Heat stress and housing systems did not cause any significant change in the level of total serum protein and sodium. Concentration of potassium and calcium was decreased in summer season. Potassium concentration was also decreased in after-noon serum sample in all the groups. Effects of heat stress and housing systems did not alter - the values of haemoglobin, PCV and R3C count. Total leukocytic count was significantly decreased during summer season. Further the after-noon blood samples also showed decrease in TLC in summer season. Absolute count of heterophil increased and lymphocytic count decreased during summer season. Number of heterophil was also increased in after-noon blood samples during summer season while, it was reverse for lymphocyte. Seasons and housing systems did not cause any significant change in the number of eosinophils and monocytes. Increase in environmental temperature directly correlated with the increase in H:L ratio and was found to be a good measure of stress to the chickens. Birds sacrificed in the after-noon during summer season showed mild fatty changes in liver and congestion in trachea and lungs. Severity of these lesions increased in the birds, died due to heat stroke. Birds under summer groups showed variable degree of hyperplasia of interrenal cells of adrenal gland. Thyroid acini were lined by flattened epithelium. More or less similar microscopic lesions were also observed in the birds, died due to heat stroke, but severity was increased. Amount of fat deposition increased in the liver samples, collected in the after-noon during summer season. Maximum mortality due to heat stroke was observed in the month of May. Increase in mortality due to FLHS was correlated directly to increase in the environmental temperature. Mortality due to FLHS v/as significantly higher in the cage birds than deep litter birds. Striking gross lesions in FLHS were highly friable and fatty liver leading to rupture and fatal internal haemorrhages. Liver sections stained with Oil Red 0 from cases of heat stroke and FLHS showed increased deposition of lipid in hepatic cells.
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Keywords
VETERINARY PATHOLOGY, A STUDY