Abstract
Twenty mature albino rats randomly assigned to two groups (n=10) were used for the study. Group A was exposed to the sun, while group B was kept under a shade. The study was for 28 days. At the end of the study, the effects of heat stress on haematology and serum biochemistry were determined. There was a significant increase (P < 0.05) in the packed cell volume of group A when compared to group B. Red blood cell count of group A increased significantly when compared to group B. The mean erythroid values for MCHC and MCH decreased significantly in group A when compared to group B. The mean haemoglobin concentration of group A was significantly lower when compared to that of group B. White blood cell count of group A decreased significantly (p<0.05) when compared to group B on day 28. The result of the differential leucocyte count showed significant decrease in lymphocytes in the heat stressed group when compared to the unstressed for the entire period. Total serum protein significantly increased in group A when compared to group B on day 14. Alanine amino transferase significantly increases in group A when compared to group B on day 28. Alkaline phosphatase decreased significantly in group A throughout the study period when compared to group B. Aspartate - amino transferase increased significantly in group A when compared to group B on day 28. Serum cholesterol significantly decreased in group A on day 28 when compared to group B.
Highlights
Most of the world’s domestic animal populations are in regions where environmental stressors adversely affect productive efficiency (Gaughan et al, 1999)
There were significant increases (p
There was a significant decrease in HBC in group A when compared with group B (Table 1)
Summary
Most of the world’s domestic animal populations are in regions where environmental stressors adversely affect productive efficiency (Gaughan et al, 1999). Clinical signs commonly observed in HS animals include decreased feed intake, body weight, blood calorigenic hormones (i.e. T4, T3) (Mitra et al, 1972; Wolfenson, 2001), and increased prolactin (PRL) levels (Wolfenson, 2001). Cattle exhibit decreased T3 and T4 concentrations (33% and 15%, respectively) during summer months but increase concentrations during winter months (Johnson and Stark, 1989). Reduced thyroid hormone levels under HS conditions are due to the complex neuroendocrine processes related to interactions among thermossensors, hypothalamus, pituitary and thyroid glands (Cooper and Washburn, 1998). Jordan (2003) observed elevated PRL levels in heifers at 32 °C, but reduced levels at 4.5 °C compared to the animals maintained at 21 oC
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