الفهرس 
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Abstract
Forty adult male New Zealand rabbits weighing 1.7 – 2 kg were used to study the pathologic and clincopathologic changes associated with the oral intoxication with zinc sulphate. Rabbits were randomly assigned to four groups (gps. 1 to 4). Rabbits of gps. 1, 2, and 3 received a drinking water solution of ZnS at doses of 100 mg/L (group 1) or 200 mg/L (group 2) or 400 mg/L (group 3) daily for 28 days. Rabbits of GP.4 were kept as a control group. Five rabbits from each group were euthanized at days 14 and 28 of the experiment. Other than mild anorexia, no significant clinical signs were observed in treated groups. The severity of pathologic lesions was dose and time-dependant. The most significant gross lesions were recorded in the livers of gp.3. The livers of these rabbits at day 14 of the experiment were diffusely pale, smaller in size, and had few multifocal pale necrotic areas that appeared slightly depressed from the liver surface. The livers of the rabbits euthanized on day 28 had mild enhanced lobular pattern and the necrotic areas were larger (1-2 mm in diameter) and appeared more prominent. The kidneys showed mild congestion with occasional mild renal cortical atrophy particularly in the rabbits of gp.3 that were euthanized at day 28. Mild to moderate hepatic changes were observed in all treated rabbits particularly those of gp.3. These changes started with mild centrilobular hepatocellular coagulative necrosis affecting few hepatocytes with hyDROPic degeneration and sporadic fatty change. On the other hand, mild to moderate infiltration of portal areas with lymphocytes, plasma cells, and rare macrophages was a constant finding in all rabbits. Sporadic hepatocellular apoptosis was present in few rabbits. Renal lesions that were recorded in treated groups were mild and included mild tubular degeneration and lympho-plasmacytic interstitial infiltration with no significant necrosis. Cerebral lesions were mild and included mild gliosis and sporadic neuronal necrosis. No significant lesions were present in the spleen, lung, heart, stomach, or the intestines of all treated groups. All rabbits of gp.3 that were euthanized at day 28th had mild to moderate testicular lesions, wherein, approximately 10-20% of available seminiferous tubules had severe degeneration and necrosis. The affected tubules had irregular shape, very thin necrotic spermatogenic epithelium and their lumens were devoid of spermatozoa. The interstitial tissue was thickened by edema, and mild infiltration with lymphocytes, plasma cells, and rare macrophages. Within the degenerated tubules, occasional spermatogenic cells were separated from the surroundings by a halo, appeared markedly smaller, had pyknotic nuclei, and indistinct cytoplasm (apoptosis). Treated rabbits from gps 2 and 3 that were euthanized at day 28 of the experiment showed a significant decrease in the hemoglobin count, packed cell volume (PCV), mean corpuscular volume (MCV), and mean corpuscular hemoglobin concentration (MCHC) when compared to the control rabbits. However, there was no significant difference in the RBCs count of the treated rabbits when compared to their control counterparts.
In conclusion, zinc sulphate in the current doses caused no mortalities or significant clinical signs except anoroxia and the resultant lesions were generally mild. However, the highest and the intermediate doses caused a mild microcytic hypochromic anemia.