Worapol Aengwanich and Suchint Simaraks

pp. 417 - 424

Abstract

The purpose of this experiment was to investigate pathological changes in broilers under chronic heat
stress. Fifteen birds (n = 15), twenty-eight days old were kept at 33 + 1oC environmental temperature for
21 days. While broilers were maintained in environmental temperature at 33 + 1 oC, body temperature,
respiratory rate and urine excretion rose. Macroscopic and microscopic lesions of heart, lung, liver and
kidney were examined. Right atrium hypertrophy with excessive blood accumulation, heart enlargement
and right ventricular hypertrophy were observed in 12 out of 15 broilers (80%). Congestion, edema and
hyperemia in lung were present in all broilers. Yellow and pale livers were observed in 4 out of 15 broilers
(26.67%). Kidneys were highly affected i.e. generalized edema and hemorrhage in subrenal capsule. Under
microscopic examination of heart, massive myofibrillar degeneration with hemorrhage, general fatty
degeneration /or/ vacuolation of myofibers and diffused myocarditis containing organisms were found in
some areas. The principal histopathologic lesions in the lung were related to vein and arteriole massive
congestion. Massive hemorrhage was largely observed in parabronchus and alveoli of all broilers.
Liver cells showed “fatty degeneration” with dilation of sinusoid of all broilers. Besides, necrosis with heterophils and lymphocytes was observed in some parts of the liver, especially in the centritubular region. In the kidney, leukocytes such as heterophils accumulated in many inflammatory areas. Fatty degeneration was
observed in renal tubular epithelia of all broilers. Glomeruli were damaged. A space between renal papillae
increased and accumulated water. Moreover, ureters in 9 out of 15 (60%) birds showed sac-like expansion
“ureteral pseudobladder”. These sacs were filled with urine and similar to bladder in mammals.