MVSc

Experimental studies were conducted on six calves keeping two as control by oral administration of sodium selenite at the rate of 1.0 mg/kg body weight thrice a week over a period of 24 weeks. Visible signs of toxicity were noticed only from week 13 onwards in experimental animals. The clinical toxicologic signs recorded were anorexia, cachexia, incoordination of gait, increased pulse and respiratory rates, pale and watery mucous membrane, subnormal temperature, cold and clammy skin, lacrimation and respiratory distress followed by recumbency and death. Laboratory evaluation of plasma protein, plasma vitamin A, haemoglobin (Hb), volume of packed red cells (VPRC), total erythrocyte count (TEC), total leucocyte count (TLC) and ascorbic acid level in the blood were carried out at weekely intervals. Since visible signs of toxicity were observed from week 13 onwards, the parameters studied were divided into 2 sets; Ist to 12the weeks (first half) and 13th to 24th weeks (second half) for statistical evaluation of data.
In experimental animals, significant reduction was observed only in respect of plasma vitamin A (P < 0.01), ascorbic acid level in blood (P < 0.01) and TEC (P < 0.05) during the first half, whereas all the parameters studied showed significant fall (P < 0.01) in the second half. The mean values of plasma protein, plasma vitamin A, haemoglobin, VPRC, TEC, TLC and ascorbic acid level in the blood in experimental animals were 7.53 + 0.09 g/dl, 30.07 + 0.59 µg/dl, 10.28 + 0.11 g/dl. 29.68 + 0.34 %, 5.16 + 0.4 mill.,/cmm, 7243.06 + 66.2 cells/cmm and 223.12 + 3.46 µg/dl respectively. The corresponding values in the control group were 7.77 + 0.07 g/dl, 32.29 + 0.48 µg/dl, 10.08 + 0.06 g/dl, 30.58 + 0.38 %, 5.42 + 0.09 mill./cmm, 7000 + 168.52 cells/ cmm and 274.38 + 1.41 µg/dl. During the second half, the mean values of the above parameters in experimental group were 6.30 + 0.13 g/dl, 22.56 + 0.38 µg/dl, 8.31 + 0.16 g/dl, 25.09 + 0.49%, 4.82 + 0.03 mill./cmm, 5905.62 + 94.14 cells/cmm and 162.32 + 4.8 µg/dl and in the control group were 7.29 + 0.04 g/dl, 32.29 + 0.48 µg/dl, 10.43 + 0.09 g/dl, 31.08 + 0.54 %, 5.58 + 0.09 mill./cmm and 7066.69 + 124.67 cells/cmm and 275.21 + 1.17 µg/dl.
The gross and microscopic pathology of internal organs in experimental animals revealed that liver is the primary organ affected followed by kidneys, heart, gastrointestinal tract and brain. The pathological lesions noticed in the liver were focal haemorrhages, fatty degeneration, centrilobular necrosis and varying degree of fragmention of hepatic cells with congestion and dialatation of capillaries. The lesions in the kidney were focal areas of degeneration, medullary haemorrhages, tubular necrosis, cloudy swelling and fatty changes. Varying degree of degeneration, necrosis and lymphocytic infiltration and replacement fibrosis were observed in the cardiac muscle. Changes noticed in the gastrointestinal tract were oedema, focal areas of haemorrhage and necrosis of the mucosal and submucosal layers.