The influence of dietary polyunsaturated fatty acids on the immune response of Atlantic salmon (Salmo salar L.)

• Main Author: Thompson, Kimberly Dawn
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 1993
• Subjects: Atlantic salmon; Atlantic salmon Feeding and feeds; Immune response Atlantic salmon; Salmo salar
• Online Access: http://hdl.handle.net/1893/29376; http://dspace.stir.ac.uk/bitstream/1893/29376/1/Thompson.pdf

The present work examined the effects of dietary (n-3)/(n-6) PUFA ratios in Atlantic salmon parr on, firstly, the fatty acid composition of lipids in peripheral blood cells and immunocompetent tissues and secondly, disease resistance. No notable differences in physiological and immunological parameters were observed between fish fed different (n-3)/(n-6) PUFA diets, except for a significantly higher number of responding B cells in kidney and spleen of the fish fed high (n-3)/(n-6) PUFA diet. The protective vaccination of the groups of fish on the different (n-3)/(n-6) PUFA ratio diets was inconclusive, but significantly more salmon died in the low (n-3)/(n-6) group when non-vaccinated fish were challenged with Vibrio anguillarum. Lipid class composition of lipids from leucocytes, erythrocytes and .serum were all found to be independent of diet, while component fatty acids were definitely influenced by dietary PUFA. Total fatty acids of the erythrocyte lipid were always high in (n-3) PUFA. Leucocyte lipid, by comparison, contained higher levels of saturated and monocnoic fatty acids, particularly 18:1 (n-9). The overall (n-6) PUFA unsaturation was higher in the lipid of leucocytes than the erythrocytes and leucocytes incorporated greater proportions of dietary 18:2(n-6) into their lipid than erythrocytes. Levels of 18:2(n-6) in the lipid of .serum and leucocytes from (n-6) PUFA fed fish began to rise after four weeks on the diet, and increased steadily until a (n-3)/(n-6) PUFA ratio of 0.8 was maintained after 16 weeks. Erythrocytes did not show diet induced modification until 8-16 weeks, at which point 18;2(n-6) fatty acid levels were observed to plateau. Influences of dietary fatty acid composition were most evident in the PC and PE fractions. Dietary 18:2(n-6) fatty acid incorporation was greater in the lipids of the lymphoid organ tissues than in leucocytes isolated from these tissues. Lymphoid tissues from (n-3) dietary group fish possessed higher (n-3)/(n-6) PUFA ratios than their leucocytes, while ...