research article: the effect of dietary fatty acids on the incidence of the redhead syndrome in white leg shrimp (litopenaeus vannamei) under environmental stress

This study aimed to examine the effect of fatty acid in the diet on changes the incidence of the red-head syndrome under temperature stress and hypoxia in white leg shrimp (litopenaeus vannamei) during 8 weeks. for this purpose, shrimps were fed  by 4 diets  (diet 1: containing 7.02% of total fat; diet 2: containing 6.41% of total fat; diet 3: containing 8.05% of total fat; diet 4: containing 6.41% of total fat with 1750 mg/kg of vitamin e), under 3 stressors (s1: no challenge to environmental stresses; s2: with hypoxic stress (2.0±1.0 ppm); s3: with increasing temperature stress (36±2°c). the results of the hypoxic stress on the incidence of redness in l. vannamei fed with different levels of fatty acids showed that there were differences significantly (p<0.05). temperature increase although showed no differences between healthy shrimps(p>0.05) but, there were significant difference among red-headed shrimp in treatment 1, 2 and 3 (p<0.05). the examination in treatments 2 and 3 showed hepatopancreatic  were loss the columnar structure so thatelongated cells and dilated tubules were observed. some b cells had no vacuoles and were not fully developed. the number of r cells was low and basophilic f cells were convex. in treatment 4, the cells have few reserves and were normal. some b cells were degenerated. the height of the tubules was lower than normal, but no inflammatory reaction was observed in the tissue. in treatment 4, cell showed  better conditions than treatments 2 and 3. accordingly, b cells were present well and r cells showed moderate storage. in general, it can be concluded that the use of vitamin e can reduce the complication of redness and minimal cell damage to hepatopancreatic tissue in l. vannamei.