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This study evaluated the dietary effects of an ultrasound-assisted extract of Origanum vulgare on the growth, antioxidant and immune responses (serum and mucosal) and resistance of zebrafish (Danio rerio) against Aeromonas hydrophila. Four hundred and forty adult zebrafish were distributed into 12 tanks and fed 4 experimental diets including 0% (control), 0.5% (M1), 1% (M2) and 2% (M3) of the extract per kg−1 diet for eight weeks. Fish were then challenged with A. hydrophila and mortality was recorded for 10 days. Results revealed that the extract exerted potent effects on growth parameters of weight gain and specific growth rate. The feed conversion ratio was significantly lower in fish fed extract-incorporated diets. O. vulgare extract improved antioxidant and immune responses, resulting in less sensitivity to oxidative stress and a higher survival rate when challenged with A. hydrophila. Overall, the greatest effects were observed in individuals with 1% dietary inclusion of the extract. These results suggest that the extract from the plant Origanum vulgare possesses a great potential to be used in the aquaculture industry and that zebrafish is an appropriate model for nutrition studies.

Three hundred rainbow trout (242.9 ± 6.9 g) were randomly assigned to 12 fibreglass tanks (25 fish/tank). The fish were fed, for 231 days (feeding level: 0.74 % average bw), four experimental diets, containing increasing levels of coconut oil: diet A 0 %, diet B 6 %; diet C 12 % and diet D 13 %, as replacements of herring oil and cod liver oil. Weight gains of fish were > 3 g d-1 and FCR lower than 1.5, for all treatments. No significant difference was observed in the main car- cass traits and whole body composition, but whole fish energy content significantly increased in fish fed diet D (10.68 KJ g-1). Different dietary fatty acid profiles had significant effects on the rainbow trout muscle contents of C10:0, C12:0, C14:0, total n-3, and the main ratios: SFA/USFA; DHA/EPA; DHA/AA, n-3/n-6, but not on total fatty acids content of the muscle

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The aim of this research was to study the main sperm characteristics of three different finfish species. Twenty-one gilt- 

head sea bream (Sparus aurata), 20 brown trout (Salmo trutta, morpha fario) and 15 rainbow trout (Oncorhynchus 

mykiss) male broodstocks, farmed under optimal conditions for each species and fed standard diets for broodstocks, were 

manually stripped. Brown trout yielded small amounts of sperm (4.5 vs18.13 ml) that were very concentrated (≅8.5 x 

109 vs 1.24 x 109 Szoa/ml) with respect to the other species. The duration of spermatozoan motility for gilthead sea 

bream sperm was significantly longer (almost 50 min), in comparison to the one-minute motility of Salmonids. Single 

fatty acids of brown trout sperm were higher than in the other two species for almost all detected fatty acids. In partic- 

ular, eicosapentaenoic acid (EPA) was at least three times more concentrated in brown trout than in rainbow trout or gilt- 

head sea bream sperm (1238.3 µg/g vs305.6 and 333.3 µg/g, respectively; P < 0.01). Saturated, polyunsaturated and 

total unsaturated fatty acid classes were significantly higher in brown trout sperm than in the other two species - almost 

double with respect to gilthead sea bream sperm and more than double in comparison to RT sperm (P < 0.01).