26This study investigated the effect on egg quality of dietary supplementation of 27 Atlantic cod broodstock with the carotenoid astaxanthin (ASTA). Duplicate groups of 28 farm-reared Atlantic cod broodstock were fed either a control diet with no added 29 ASTA, or an ASTA supplemented diet (73.7 mg/kg dry weight; Carophyll Pink®) for 30 2 months prior to peak spawning. The results indicated that ASTA uptake into eggs 31 from the broodstock diet was highly efficient.

We studied the performance of cod rearing in which live feed was given under three different essential fatty acid (EFA) enrichment regimes, using commercially available live-feed enrichments. We assessed the fatty acid profile [docosahexaenoic (DHA), eicosapentaenoic (EPA), and arachidonic acid (AA)] in larval somatic tissue, relative to its amounts in both rotifers and Artemia as well as to larval performance. Overall, percentage lipid level of each experimental diet for the trial was approximately 50%. Further, there were no significant differences in total fatty acid levels of larvae from each treatment at the end of the trial (mean = 444.76 μg fatty acid per mg lipid). However, during the rotifer phase, larvae from each treatment were able to incorporate comparable levels of %DHA, irrespective of levels in the diet. Despite this, the rotifer diet with more %DHA still promoted better larval growth than other treatments. Conversely, larvae from two of the treatments did not exhibit any accumulation of AA, reflecting levels found in the diet instead. However, between-tank differences in larval %AA showed improved growth during the rotifer period when larval %AA was high. Low ratios of EPA had no effect. During the Artemia phase, percentage levels of larval DHA decreased; there was no accumulation of DHA relative to dietary levels, which in Artemia were significantly lower than in rotifers (6 cf. 20–30%). However, DHA levels in larvae at the end of the experiment correlated positively with survival. Artemia contained lower levels of AA than rotifers (1.5 cf. 3.0%), yet comparable levels of AA were found in rotifer-fed and Artemia-fed larvae. This also differed significantly between treatments, and correlated positively with survival.

The efficacy of a single cell protein (SCP) methanotroph (Methylococcus capsulatus, Bath) bacteria meal (FeedKind®, Calysta, Menlo Park, CA, United States), in Pacific white shrimp (Penaeus vannamei) diets was studied to determine growth performance, survival rate and disease resistance against Vibrio parahaemolyticus causing Acute Hepatopancreatic Necrosis Disease (AHPND). The growth trial was assigned in a completely randomized design (CRD) with four treatments and 5 replicates of each, T1: a fishmeal-based control containing 15% fish meal and 3 diets with graded levels of methanotroph bacteria meal, namely T2: 5% methanotroph bacteria meal, T3: 10% methanotroph bacteria meal, and T4: 15% methanotroph bacteria meal. Shrimp were fed ad libitum for 6 weeks on trial diets to assess growth. Subsequent to the growth trial, three replicates of the same groups were exposed to V. parahaemolyticus by a single bath challenge and held for a further 15 days on the same diets as the growth study to assess survival and resistance. No significant differences (p > 0.05) in survival or in growth performance, including final weight, weight gain, specific growth rate, feed consumption or feed conversion ratio of white shrimp fed feeds containing methanotroph bacteria meal or control diets for 6 weeks. Immune markers such as hemocyte counts, phenoloxidase, superoxide dismutase and lysozyme activity were similar across all groups after the 6-week feeding trial. In a V. parahaemolyticus challenge, methanotroph bacteria meal in the diet significantly promoted the survival rate, and the reduction of Vibrio sp. in the hepatopancreas of white shrimp. Hemocyte count and phenoloxidase activity showed no significant differences (p > 0.05) between diet treatment groups, but hemolymph protein was significantly higher (p < 0.05) in shrimp fed diets containing 15% methanotroph bacteria meal after challenge. The Vibrio colony counts from hepatopancreas in the treatment groups were all significantly lower than the control (p < 0.05). The findings show that methanotroph bacteria meal can entirely replace fishmeal in white shrimp diets and the 15% inclusion of methanotroph bacteria meal in shrimp diet shows no adverse effects on growth performance, feed utilization and survival rate. In addition, shrimp fed methanotroph bacteria meal diets exhibited improved survival rates to an AHPND challenge.