Effect of using a fat mixture to replace partial to total fish oil in diets for Litopenaeus vannamei

Abstract

The present work aimed at evaluating if a mixture of different fat sources could replace fish oil in diets. Consequently, a mixture of poultry, palm kernel, and microalgae fat sources was blended (25, 71 and 4%) to replace fish oil at four different levels; 0 (Control), 25 (L-Mix), 50 (M-Mix), and 100% (H-Mix). Then, four different diets with defatted poultry by-product meal (PBM) and fish meal (FM), were used to formulate isoproteic and isolipidic diets. Juveniles of Litopenaeus vannamei (2.2 ± 0.3 g) were aleatorily distributed into 12 experimental units (500 L) in a recirculation system (RAS) with temperature controlled (28 °C) and constant aeration. After seven weeks of the experimental procedure, differences were found only in the survival rate and hepatosomatic index. The survival rate was 92% for M-Mix and H-Mix, while 70% was registered in the Control group. The hepatosomatic index was higher in the H-Mix (5.5) than in the rest of the dietary groups, with a minimum amount in the Control group (3.7). Even if no significant differences were found in the feed conversion ratio using an ANOVA (P = 0.5), a significant linear correlation revealed that a lower FCR (1.08) was registered in H-Mix compared to the Control (1.8). The fatty acid analysis demonstrated that those shorter than 14 carbons were efficiently utilized, as lauric acid (12:0) was observed lower in the hepatopancreas than in the supplied diets. In general, the rest of the fatty acids were used as reflected by their content of diets. On the contrary, the arachidonic acid (ARA) was efficiently accumulated in shrimps fed the three experimental diets despite its low concentration in the experimental treatments. In contrast, EPA and DHA were slightly lower than in the corresponding dietary treatments. It is concluded that the fat mixture containing poultry and palm kernel fats, with a DHA source from microalgae, resulted in a better survival rate and equal growth rate to shrimp reared with diets containing fish oil. Notwithstanding study results, it is recommended to research with higher amounts of medium-length fatty acids in diets together with attractants to increase feed ingestion.