Influence of dietary phospholipid level and bile salt supplementation on larval performance of Atlantic cod (Gadus morhua L.)

Abstract Lipid nutrition in Atlantic cod ( Gadus morhua ) larvae remains poorly understood, which poses challenges for optimizing commercial diets for cod larviculture. This study investigated the effects of two dietary phospholipid (PL) levels (~ 6 vs. 7 % dry matter, dm) and bile salt (BS) supplementation (0 vs. 0.04 % dm) on growth, survival, skeletal development and anomalies, and biochemical composition of cod larvae. A 2×2 factorial design was applied using four isolipidic and isoproteic formulated diets during co-feeding (17–34 days post-hatching, dph) and until termination of the experiment at 61 dph: high PL (HPL), high PL with BS (HPL-BS), low PL (LPL) and low PL with BS (LPL-BS). While final body sizes did not differ among the groups, larvae fed high-PL diets showed slightly higher specific growth rates and more ossified dorsal and anal fins and vertebrae, implying improved skeletal development. Larvae fed low-PL diets contained more n-3 polyunsaturated fatty acids, including 22:6 n-3 and 20:5 n-3, in their triacylglycerols, possibly due to lower capacity to utilize these fatty acids for growth and development. Supplementation of BS had no clear effects, suggesting that lipid digestibility in cod larvae is not limited by endogenous BS from the Liver and that dietary BS is unnecessary in diets with 22 % dm lipid, of which 61–68 % are neutral lipids. Our findings emphasize the importance of including adequate amounts of PLs in cod larval diets, while the role of dietary BS requires further investigation.