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Two separate 8 week feeding trials were conducted to examine the impacts of fish meal replacement with an organically certifiable yeast-based protein source with and without supplementation of methionine, tryptophan, and taurine to diets for juvenile cobia. In the first trial, diets were formulated to contain 41% crude protein and 13% lipid, and a yeast-based protein replaced fish meal at 50 and 75% of dietary protein with and without supplemental taurine at 0.5 g/100 g dry diet. The control diet contained 100% herring fish meal. Methionine and tryptophan were added to all diets except the control to resemble the amino acid profile of fish meal. Results from this study indicated that fish fed diets supplemented with taurine exhibited significantly higher weight gain and better feed efficiencies than all other fish. Diet significantly impacted biological indices such as muscle ratio (MR), visceral somatic index (VSI), and hepatosomatic index (HSI). The 75% yeast-based protein diet without taurine returned the lowest MR values and the highest VSI and HSI values. In the second trial, diets were formulated to contain 43% crude protein and 11% lipid, with the control diet containing 100% herring fish meal and the same yeast-based protein replacing fish meal at 50, 75, and 100% of dietary protein. All diets except the control were supplemented with taurine at 0.5 g/100 g dry diet. Results from this study indicated that increasing amount of yeast-based protein led to decreased weight gains and feed efficiencies regardless of taurine supplementation. However, weight gain and feed efficiencies did increase when compared to a previous study [Lunger, A.N., McLean, E., Craig, S.R., 2007. The effects of organic protein supplementation upon growth, feed conversion and texture quality parameters in juvenile cobia (Rachycentron canadum). Aquaculture 264, 342–352] using identical diet formulations except for taurine supplementation. MR values tended to decrease while VSI and HSI values tended to increase with increasing fish meal replacement. It is obvious from the results from both of the present studies that taurine supplementation does have a significant impact on growth and feed efficiency of juvenile cobia when they are fed diets containing high levels of plant-based proteins as

Sixty juvenile cobia ( Rachycentron canadum ; 28.3 ± 0.13 g wet wt) were randomly distributed into each of 12 tanks in a recirculation unit ( n = 5 tank − 1 ). Fish were fed one of two diets (47:8 or 47:20 protein:lipid) at 6–8% body wt d − 1 for 6 weeks. Each week, the composition of fish ( n = 5) from each dietary treatment was calculated by measuring the impedance (resistance and reactance) of a current ( x μA AC and kHz) passed through a live animal. Electrodes were positioned at morphologically discrete points on the dorsal left hand side of the animal. After bioimpedance (BIA) assessment, the identical fish were sacrificed and their body composition determined using traditional, chemical methods. Results generated by chemical analyses were regressed against BIA data. Linear regression analysis was performed utilizing compositional analysis (protein, lipid and ash) as the observed values and BIA assessment for the predicted. Regressions for each body composition parameter produced high correlations in all relationships: resistance (in parallel) and protein (adj. R 2 = 0.9569), resistance (in parallel) and total body water (adj. R 2 = 0.9894), reactance (in parallel) and total body ash (adj. R 2 = 0.8547), reactance (in series) and dry matter (adj. R 2 = 0.9272) and reactance (in series) and fat-free mass (adj. R 2 = 0.9916). The F value tests ( P

An eight week feeding trial was conducted to examine the impacts of organically certifiable alternate protein sources on growth, feed efficiency, biological indices, fillet proximate composition and fillet quality in juvenile cobia. Diets were formulated to be isonitrogenous and isocaloric. The control diet provided 45% crude protein from Special Select® menhaden fish meal and 10% total lipid. The remaining diets were formulated with 25 and 40% inclusion of NuPro® (an organically certified yeast-derived protein source), and 40% inclusion of organically certified soybean meal, soybean isolate, or hemp seed meal. Two additional diets were formulated to contain a mixture of all organic protein sources at 23% with 8% fish meal or 25% and no fish meal. Diets were fed to triplicate groups of juvenile cobia (initial weight 10 g/fish) in 300 L circular tanks connected as part of a recirculating aquaculture system. Weight gain ranged from 167 to 1138% increase from initial weight and was similar for all fish fed diets containing 40% of any given alternate protein source. Fish fed the blended diet with 8% fish meal exhibited significantly lower weight gain, SGR, and FE ratio values than all other fish. Cobia fed the diet without any fish meal did not survive to the end of the study. Biological indices such as muscle ratio (MR), visceral somatic index (VSI), and packed cell volume (PCV) were all similar between fish fed the control diet and those fed diets with up to 40% alternate protein. Fish fed the diet with only 8% fish meal had significantly lower MR, PCV, and plasma protein, and significantly higher VSI. All fish exhibited similar fillet proximate composition for protein, lipid, dry matter, and ash except for those fed the diet containing 8% fish meal. Alternate protein source did appear to impact the fillet texture of cobia. Generally speaking, plant protein sources returned higher textural characteristics than the fish meal control. At all time points and all texture parameters, cobia fed the diet containing hemp seed meal returned the highest values except for distance to rupture in the final time point. Results indicate that up to 40% fish meal protein can be replaced by any of the organically certifiable alternate proteins that were used in this study without detrimental impacts to weight gain, feed efficiency, biological indices, or fillet composition in juvenile cobia. Our results also suggest that alternate proteins have differential effects upon final product quality, which may have implications in terms of cobia processing and development of industrial products. © 2007 Published by Elsevier B.V.

The effect of stocking density upon the hydrodynamics of a circular tank, configured in a recirculation system, was investigated. Red drums Sciaenops ocellatus of approximately 140 g wet weight, were stocked at five rates varying from 0 to 12 kg m-3. The impact of the presence of fish upon tank hydrodynamics was established using in-tank-based Rhodamine WT fluorometry at a flow rate of 0.23 l s-1 (tank exchange rate of 1.9 h-1). With increasing numbers of animals, curvilinear relationships were observed for dispersion coefficients and tank mixing times. Stocking densities of 3, 6, 9 and 12 kg m-3 resulted in a 0.2-, 0.5-, 2.4-, and 3.2-fold decrease in mixing time relative to that observed for empty tanks (Pb0.001). Udgivelsesdato: APR 28 The effect of stocking density upon the hydrodynamics of a circular tank, configured in a recirculation system, was investigated. Red drums Sciaenops ocellatus of approximately 140 g wet weight, were stocked at five rates varying from 0 to 12 kg m-3. The impact of the presence of fish upon tank hydrodynamics was established using in-tank-based Rhodamine WT fluorometry at a flow rate of 0.23 l s-1 (tank exchange rate of 1.9 h-1). With increasing numbers of animals, curvilinear relationships were observed for dispersion coefficients and tank mixing times. Stocking densities of 3, 6, 9 and 12 kg m-3 resulted in a 0.2-, 0.5-, 2.4-, and 3.2-fold decrease in mixing time relative to that observed for empty tanks (Pb0.001).

A six-week feeding trial was conducted to evaluate the use of a yeast-based, certified organic protein source as a replacement for fish meal in diets for cobia. Five experimental diets were formulated to provide 40% crude protein and 11% dietary lipid (dry matter basis) with the yeast-based protein source replacing Special Select® menhaden fish meal at 25%, 50%, 75% and 100% of dietary protein. Ten juvenile cobia (initial weight 11.5 g/fish) were randomly stocked in triplicate 300 l circular fiberglass tanks ( n = 30 treatment − 1 ) and hand-fed the diets based upon total tank biomass two times daily at 0900 and 1400 h. Fish were group weighed weekly to monitor performance and adjust feeding rations. Water temperature and salinity were maintained at 27 °C and 15‰, respectively. At the end of the feeding trial, weight gain, ranging from 86% to 512%, and feed conversion ratio values, ranging from 1.9 to 5.8, were significantly affected by the inclusion of the yeast-based protein source, with decreasing values as inclusion levels of the yeast-based protein source rose above 25% of dietary protein. Cobia fed the diet containing 25% of dietary protein from the yeast-based protein source had equal weight gain and feed conversion ratio values as fish fed the control diet composed of 100% fish meal (503 vs. 512 and 1.9 vs. 1.9, respectively). Biological indices including hepatosomatic index, visceral somatic index and muscle ratio were all similarly affected by inclusion of the yeast-based protein source, with significant impacts when inclusion levels rose above 25% of dietary protein. As with the weight gain and feed efficiency ratio values, fish fed the diet containing 25% of protein from the yeast-based source had similar values as those observed in the control animals. This study represents the first attempt to utilize an organically certified protein source as a replacement for fish meal in diets for juvenile cobia. Although levels of inclusion of the yeast-based protein source above 50% of dietary protein resulted in detrimental effects on production characteristics, the data clearly suggest that, at a minimum, 25% of dietary protein can be provided by this yeast-based protein in diets for cobia.