Effects of the ration of linoleic acid to linolenic acid dietary to tilapia females (Oreochromis niloticus)

Abstract

Polyunsaturated fatty acids (PUFAs) and their long chain derivatives (LCPUFA) are involved in various functions in the body. However, an adequate balance between dietary n-3 and n-6 fatty acids (FA) from plant sources, may prevent possible competition in their biosynthetic routes. The objective of this work, was to evaluate the effect of different dietary linoleic acid/ linolenic acid (LA/ LNA) ratio for Nile tilapia (Oreochromis niloticus) breeding females. An experiment was performed using 24 males and 72 females with mean initial weight of 131.3 g and 124.4 g, respectively. Six females and two males were distributed in twelve tanks of 250L each. The design was completely randomized, with four treatments (20.1, 4.5, 3.9 and 0.7 LA / LNA) and three replications. Observations were made for the occurrence of spawning every day. At the end of the test, blood and tissue samples were collected. Fish fed the 3.9 and 0.7 LA/LNA diets had higher number of eggs produced (p<0.05). Hatch rates and larval survival were not affected by the treatments (p>0.05). Specific growth rate was highest in fish fed the 0.7 LA/LNA ratio and hepatosomatic index was highest in fish fed the 4.5 LA/LNA ratio (p<0.05). In general, the FA profile of gonads reflected the composition of the diet. The arachidonic acid content was higher in 20.1 ratio and the eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids concentration were higher in 0.7 ratio (p<0,05). Diets did not influence the triglycerides content in plasma (p>0.05). However, higher levels of cholesterol were observed in fish fed 4.5 and 3.9 LA/ LNA ratio (p<0.05). The highest dietary LA levels increased the gene expression of cyp17, while the dietary 3.9 LA/ LNA ratio promoted highest expression of cyp19a1a (p<0.05). In conclusion, a 3.9 LA/ LNA ratio should be used for Nile tilapia female.