EFFECT OF FISHMEAL REPLACEMENT WITH SAND SMELT MEAL ON FATTY ACID COMPOSITION OF NILE TILAPIA FRY Oreochromis niloticus
The efficiency of the various alternative animal or plant protein sources as replacements for fish meal (FM) have been evaluated in various freshwater or marine fish diets. However, there are concerns that the extensive replacement of fish meal in freshwater fish diets could adversely affect on the fatty acid requirements or quality of the fish meat. Among the different protein sources of animal origin, sand smelt meal (SSM) is a rich protein source (>70% dry matter). This experiment was conducted to study the effect of replacement of fish meal (FM) with SSM in diets on fatty acid composition of tilapia fry, Oreochromis niloticus. Five diets were formulated to be isoproteic and isoenergetic diets replacing 0, 25, 50, 75, and 100% FM protein by SSM protein (Table 1).
Fish, initial average weight of 0.134 0.65 g fish-1 were fed twice daily to apparent satiation throughout the duration the trial (13 weeks). According to results, replacement of FM with SSM slightly modifies the dietary fatty acid profile. As the FM content decreases, there is a light reduction of saturated fatty acids (SFA), the diet with lowest FM protein percentage having the highest polyunsaturated fatty acids (PUFA) and lowest monounsaturated fatty acids (MUFA) proportions (Table 2). No significant differences were found for the main fatty acid compositions in experimental fish, although some changes could be observed for some particular fatty acids. FM replacement with SSM increases the fish PUFA content, mainly due to 18:2n-6, which is present in high quantities in SSM. It was noted that fish meat was moderately high in n-3/n-6, although n-3/n-6 content was low in the experimental diets. This phenomenon may confirm that tilapia may be capable of converting short chain, more saturated FAs into long chain. As a consequence, compared with fish fed the control diet, the inclusion of SSM was not caused a significant difference for the main fatty acid composition in Nile tilapia fry.
Fish, initial average weight of 0.134 0.65 g fish-1 were fed twice daily to apparent satiation throughout the duration the trial (13 weeks). According to results, replacement of FM with SSM slightly modifies the dietary fatty acid profile. As the FM content decreases, there is a light reduction of saturated fatty acids (SFA), the diet with lowest FM protein percentage having the highest polyunsaturated fatty acids (PUFA) and lowest monounsaturated fatty acids (MUFA) proportions (Table 2). No significant differences were found for the main fatty acid compositions in experimental fish, although some changes could be observed for some particular fatty acids. FM replacement with SSM increases the fish PUFA content, mainly due to 18:2n-6, which is present in high quantities in SSM. It was noted that fish meat was moderately high in n-3/n-6, although n-3/n-6 content was low in the experimental diets. This phenomenon may confirm that tilapia may be capable of converting short chain, more saturated FAs into long chain. As a consequence, compared with fish fed the control diet, the inclusion of SSM was not caused a significant difference for the main fatty acid composition in Nile tilapia fry.