COBIA (Rachycentron canadum)

with the MG diet would be greater, this cost could be offset by the 15% reduction in rearing timerequired as compared with the HSB and GOLD diets.277. Wills, P.S., Weirich, C.R., Baptiste, R.M. & Riche, M.A. (2013). Evaluation of commercialmarine fish feeds for production of juvenile cobia in recirculating aquaculture systems. NorthAmerican Journal of Aquaculture, 75(2), 178-185.The effect of different commercially available marine fish diets on production characteristics andbody composition of juvenile cobia Rachycentron canadum reared in production-scale recirculatingaquaculture systems was evaluated in a 57-d growth trial. Juvenile cobia (mean weight ± SE, 26.7 ±0.9 g) were stocked at an initial density of 1.2 kg/m 3 . After stocking, fish were fed one of threeclosed-formula diets formulated for carnivorous marine finfish (coded diet A, 50% crude protein :22% crude lipid; diet B, 49% crude protein : 17% crude lipid; and diet C, 48% crude protein : 17%crude lipid), all at a targeted feed rate of 3–5% body weight per day. At 2-week intervals, 10% ofthe population of each tank was sampled to determine mean weight, weight gain, specific growthrate, feed conversion efficiency, and biomass. At the termination of the trial, the entire populationof each tank was harvested to determine the same characteristics and survival. In addition, fish weresampled to determine relative changes in whole body composition, energy retention, proteinefficiency ratio, and protein productive value. Final weight (203.3 g), specific growth rate (3.6%/d),feed conversion efficiency (92.2%), biomass (7.3 kg/m 3 ), and protein productive value (25.2%) offish fed the high-lipid diet A were significantly higher than those of fish fed the other two diets. Nodifferences in whole body composition were observed among fish fed the three diets with theexception of dry matter composition. Contrary to previous reports, the results of the current studyindicate that juvenile cobia reared in production-scale recirculating aquaculture systems fed highlipiddiets exhibit protein sparing and better growth.278. Woitel, F.R., Trushenski, J.T., Schwarz, M.H. & Jahncke, M.L. (2014). More judicious use offish oil in cobia feeds: I. Assessing the relative merits of alternative lipids. North American Journalof Aquaculture, 76 (3), 222-231.Limited availability and high prices underscore the need to use fish oil more judiciously inaquafeeds. Most alternative lipids contain little to no n-3 long-chain (LC) polyunsaturated fattyacids (PUFAs). If alternative lipids are fed exclusively, growth performance may be impaired andtissue fatty acid composition may be altered in fish such as the cobia Rachycentron canadum.Alternative lipids that are rich in saturated fatty acids (SFAs) and monounsaturated fatty acids(MUFAs) may increase the efficiency of LC-PUFA metabolism and may limit or attenuate thetissue LC-PUFA loss associated with fish oil sparing. Cobias (weight [± SE] = 77.4 ± 0.2 g) werefed diets containing either fish oil (control) or a 50/50 blend of fish oil and standard soybean oil,partially hydrogenated soybean oil, fully hydrogenated soybean oil, pork lard, or beef tallow. After8 weeks, the feed conversion ratio (mean ± SE = 1.56 ± 0.04), weight gain (180 ± 6%), and specificgrowth rate (1.83 ± 0.04% of body weight/d) were equivalent among groups. Dietary fatty acidprofiles influenced tissue composition; fatty acid profiles of control fish were more similar to thoseof fish that received higher levels of SFAs and MUFAs than to those of fish that were fed higherlevels of C 18 PUFAs. The SFA- and MUFA-rich lipids, such as fully hydrogenated soybean oil andbeef tallow, may be useful in reducing the fish oil quantities needed in cobia feeds whilemaximizing fillet LC-PUFA content.279. Xiao, L.D., Mai, K.S., Ai, Q.H., Xu, W., Wang, X.J., Zhang, W.B. & Liufu, Z.G. (2010).Dietary ascorbic acid requirement of cobia, Rachycentron canadum Linneaus. AquacultureNutrition, 16(6), 582-589.A 10-week feeding trial was conducted to determine the optimal requirement of cobia(Rachycentron canadum Linneaus) for dietary ascorbic acid (AA). Graded levels of L-ascorbyl-2-polyphosphate (LAPP) were supplemented in basal diet to formulate six semi-purified dietscontaining 2.70 (the control diet), 8.47, 28.3, 80.6, 241 and 733 mg AA equivalent kg -1 diet,respectively. Each diet was randomly fed to triplicate groups of fish in flow-through plastic tanks(300 L), and each tank was stocked with 25 fish with average initial weight of 4.59 ± 0.36 g.Observed deficiency signs included poor growth, higher mortality and lower feeding rate (FR) inthe fish of the control group. Fish fed the control diet had significantly lower weight gain (WG),lower feed efficiency ratio (FER) and lower tissue AA concentrations in fish liver and muscle. Withthe increase of dietary AA, the survival, WG, FER, hepatic and muscular AA concentrations ofcobia significantly increased and then levelled off. The dietary AA requirement of cobia was86