الفهرس 
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Abstract
The present study was carried out to highlight the toxic effects of aflatoxin B1 and ochratoxin A on humoral and cell-mediated immune responses of broilers . Also , evaluation the efficacy of MOS to ameliorate the toxic effects of AFB1.
For a such purpose, the following points were investigated :
1- Humoral immune response.
The serum samples from each group were obtained and haemagglutination inhibition titre against NDV was recorded.
2- Mitogenic response of peripheral blood lymphocytes to PHA.
3- Total leucocytic counts.
- The results revealed that there was no significant effect of levels of 250 ppb AFB1 and 400 ppb OTA on antibody titre against NDV.
- There was a significant diminished response of PBL to PHA.
- Investigation of total leucocytic count revealed lymphocytopenia and heterophilia.
4- Investigation of serum biochemical parameters, the results showed that 250 ppb AFB1 and OTA ppb 400 caused a significant increase in serum uric acid & creatinine and levels of serum liver enzymes such as ALT, AST, GGT and ALP. While a significant decrease of serum total protein, albumin and globulin.
5- Histopathological examination of the liver, kidney, spleen, thymus, bursa, heart and lung. Grossly, the liver was pale in color and enlarged. Also the kidney was enlarged and have some haemorrhagic patches. Microscopically, the liver showed proliferation of bile duct epithelium, coagulative necrosis of hepatocytes. The kidney revealed degenerative changes including necrosis and destruction of renal tubules with proliferation and / or infiltration of lymphoid cells in the interstitial tissue.
Moreover, lymphoid depletion and apoptosis of lymphoid cells were noticed in the spleen & thymus and atrophy of lymphoid follicles of bursa. The lesions became more severe with prolonged exposure time.
6- Dietary supplementation of 1 gm MOS/Kg diet during afltoxicosis could ameliorate some of the toxic effects of AFB1 in broilers. It could improve some of serum biochemical alterations by increasing serum total protein and albumin. While, it decreases the levels of serum uric acid, creatinine and activities of liver enzymes. Also, it has a protective action on different tissues, liver, kidney, spleen, thymus, bursa and lung showed normal histological architecture while the heart showed mild coagulative necrosis in some myofibril.
from the above results it could be concluded that:
- Using 250 ppb AFB1 or 400 ppb OTA might not show any adverse effects on humoral immune response under experimental conditions, however, these concentration may suppress humoral immune response and decreases host resistance to infectious diseases under farm conditions.
- Adding AFB1 and OTA with mentioned doses might not causes mortality in broiler but these myctoxins are harmful to poultry and can greatly affect their general health and productivity through alterations in the functioning of immune system. These adverse effects of mycotoxicosis resulting in economic losses to poultry industry.
- The severity of pathological and clinicopathological alterations was related to the dietary levels of the used myctoxins, duration of exposure and age of birds.
- Contamination of broiler diet with AFB1 and OTA increases the stress response in broilers due to adverse effect on leukocytic count, heterophils and lymophocytes (H/L ratio).
- The immunosuppressive effects of AFB1 and OTA on broilers confirmed by the decreased immune response, depletion of lymphatic follicles in the bursa with hypoproteinemia.
- Supplementation of MOS partially alleviated the toxic effect of aflatoxin B1 along with better cell-mediated immune response with mild or nearly no histopathological lesions and improve some of the serum biochemical alterations associated with aflatoxicosis. These findings could be attributed to immunostimulant potential of MOS
- Attention must be taken to avoid mycotoxicosis under farm conditions as mycotoxins not only harmful to poultry but also it has a dangerous effect on human because its residual and cumulative nature.