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Abstract
Some studies on the immune status of cultured Oreochromis niloticus Lysine and methionine deficiency in cultured fish considred as one of the most notable nutritional constraints on the expansion of aquaculture and the realization of its full potential. Lysine and methionine deficiency causes a poor growth rate implies that the immune responsiveness would be markedly impaired . Few studies, however, have been concerned with the effect of nutrients on the immune response. A dietary deficiency leads to immune suppression in fish . Inducing a protective immune response to a pathogenic organism before the individual fish becomes naturally exposed to it (Prophylaxis) seems at first sight an eminently sensible way of preventing an infectious. Improving feed efficiency, metabolic assimilation, immunity and minimizing mortality in fish farms through improvement of fish immunity against different fish diseases, is of high priority in contemporary animal production and it will cause reduction in production costs and improvement of fish production with minimizing feed costs.
Therefore, the present work was designed to investigate :
The effects of methionine and lysine amino acids deficiency on freshwater fish production and immunity through study :
The effect of methionine and lysine deficiency on: body weight, body weight gain, feed conversion and efficiency.
b. The effect of methionine and lysine on the immunity through study the effect of the deficiency of them on differential leucocytic counts, phagocytic activity and index .
c. The effect of methionine and lysine deficiency on tissues through histopathological studies and clinical studies as serum enzymes as sALT, sAST and Total proteins as well as serum bactericidal and lysozomal activity. The effect of methionine and lysine deficiency on protection against infection by A. hyDROPhila by calculating relative level of protection and antibody titers after vaccination by bacterin of the same strain of A. hyDROPhila.
This study was carried-out on a total number of 120 healthy fish Oreochromis niloticus, were obtained from private fish farm. The fish were in good healthy condition without any clinical manifestation . Fish were transported a live to the laboratory Departement of Poultry and Fish Disease of Faculty of Veterinary Medicine, Alexandria Univeristy in plastic bags containing water enriched by air (2/3).Average body weight of fish about 50 ± 5 g.
The results of this study concluded that:
1. Deficiency of methionine and lysine causes decreasing of body weight, body weight gain and fed conversion than the control group.
2. The most important clinical signs of fish due to methionine and lysine deficiency include severe emaciation, lethargy, decreasing immunity against different diseases. In addition to, appearance of nervous signs, haemorrhages on the body surfaces with exophthalmia.
3. The post-mortem examination revealed the presence of enlargement of different body organs in addition to presence of the bloody fluid in the abdomen.
4. The most important Histopathologic results indicated that, the nature of the encountered lesions due lysine and methionine deficiency depend up on concentration of the methionine and lysine and if the deficiency lysine only or methionine only or both with each other.
5. The results of haematological studies indicated that, the lymphocytes, monocytes, basophils and eosinophils percentages decreased severly in deficiency of methionine and lysine followed by methionine only but the deficiency of lysine not affected severly on lymphocyte , but its effect on monocyte and basophils is severly than the methionine deficiency.
6. The results of WBCs, RBCs and PCV % count indicated that the total WBCs count decreased severly in deficiency of lysine and methionine, followed by lysine deficiency and all of them lower than the control group.
7. The Hb % indicated that, there is a severe decrease in its concentration in methionine deficiency followed by lysine deficiency followed by deficiency of both lysine and methionine and all of them of lower concentration than the control group.
8. The obtained results indicated that deficiency of methionine and/or lysine causes degredation of the lymphoid tissue in the fish that causes decrease of the blood cells.
9. The level PA and PI showed severe decrease in deficiency of methionine and lysine, followed by lysine deficient group then the methionine deficient group and all of them lower than that of the control group.
10. The significant (P< 0.01) decrease of phagocytic activity and phagocytic index of methionine and/or lysine deficiency or both attributed to the destructive effect of their deficiency on liver, kidney, spleen and other haemopiotic organs , so it causes leucocytpenia and decrease the phagocytic activity and phagocytic ndex.
11. The serum enzymatic examination GOT (AST) and GPT (ALT) concentration of serum enzyme levels of the O. niloticus fed on diet of different concentrations of methionine and lysine. The GOT and GPT showed that, the higher level in methionine and lysine deficient diet treated group followed by methionine deficient group, and then lysine deficient group and the lower level of GOT and GPT observed in control group that fed diet complete in all nutritional requirement.
12. The Total serum protein, Albumin, Globulin and Albumin/Globulin ratio (Serum proteins). The level of Total protein, albumin and albumin / globulin ration showed a higher level in control group. Meanwhile the lower level observed in the groups fed on methionine and lysine deficiet diet.
The bacterial activity and lysozyme activity indicated that, the bacterial activity and lysozyme activity achieved higher level in control group followed by lysine deficient group and the lower level observed in methionine deficient group and methionine + lysine deficient group.