Department of Veterinary Pathology, Rajasthan University of Veterinary and Animal Sciences, Bikaner 334001 (Rajasthan).
The zinc is one of the major trace mineral essentially required for the normal growth of various body tissues especially of epithelium of various organs of digestive tract in animals. In clinical observations, the zinc deficiency has also been found to result in an increased susceptibility to a variety of infectious disorders as well as decreased cell mediated immunity causing significant impairment of cellular and humoral immune response. The various factors causing clinical or subclinical deficiency of this mineral in various animal species hinders performance by affecting a number of body functions including retardation of growth, inappetance, alopecia, impaired development and functions of different organs. The present study had been carried out to delineate the immunosuppression occur due to experimental zinc deficiency on the immune system of rats including spleen, thymus and lymph nodes alongwith their histopathological alterations. The present investigation was conducted on 48 male weanling albino rats divided into two groups offered zinc deficient and zinc adequate purified diets, respectively. Blood samples of each rat were collected on 0, 7, 14, 21 and 28th day of experiment for haematological, biochemical, bacteriological and immunological examinations. On 28th day of experiment, all survived animals in different groups were sacrificed and portions of organs were collected for histopathological examination. Differential leucocyte count indicated that the mean per cent values of lymphocytes showed a significant decrease due to deficiency of zinc in the diet. Respectively, an increase in neutrophil count and decrease in lymphocytes count were observed due to effect of period. Regarding sub- treatments given to both the dietary groups, a significant increase in neutrophils and decrease in lymphocytes count due to S. aureus infection. Histopathological observations of organs related with immune system of body described that in zinc deficient animals, the spleen sections revealed reduction in the number and size of white pulps due to depletion of lymphocytes and proliferation of reticular cells in red pulp. In the spleen section of zinc deficient infected animals. The sections of thymus exhibited depletion of lymphocytes and growth retardation of lymphoid tissue along with increase in the number of macrophages. Sections of mesenteric Lymph node revealed in zinc deficient animals, there was depletion of most of the lymphocytes along with proliferation of histiocytes and reticular cells. In some cases, germinal centres were intact but had microscopic foci. These observations were suggestive of decreased immunity and support the hematological changes observed during zinc deficiency.
