Effect of the dietary linoleic/α-linolenic ratio (n6/n3) on histopathological alterations caused by suboptimal temperature in tilapia (Oreochromis niloticus)

Tilapias are produced worldwide, including subtropical areas. In turn, dietary fatty acids can enhance resistance under cold stress. The present study reports the nutritional effect on suboptimal temperature tolerance based on histopathological alterations in tilapia (Oreochromis niloticus). Fish (initial weight: 34.02 +/- 0.79) were exposed to two different temperatures (20 degrees C and 30 degrees C) for 30 days. Under both conditions, fish were fed two different diets based on the linoleic/alpha-linolenic ratio (n6/n3 = 12.02 and n6/n3 = 3.85). The most important alterations in liver caused by temperature included high cellular hyperplasia in fish at 30 degrees C (P < 0.05). Suboptimal temperature also caused gills aneurysm, lamellar lifting and low hyperplasia (P < 0.05). Cytoplasmic vacuolization decreased and nuclear displacement increased in the fish fed n6/n3 = 3.85. (P < 0.05). Suboptimal temperature provided high gills aneurysm, epithelial lamellae lifting and low lamellar hyperplasia (P < 0.05). Conversely, the fatty acid content (n6/n3 = 3.85) in the diet provided low lamellar lifting and fusions (P < 0.05). Finally, tilapia showed an increased glycogen storage trend in gills and muscle at low temperature (P < 0.05). Our study suggests that when feeding tilapia a high dietary n3 content, this fish is able to respond to suboptimal temperature in subtropical aquaculture facilities.