Fillet Protein Research Articles

Feeding Frequency Affects Growth, Not Fillet Composition, of Juvenile Sunshine Bass Morone chrysops×M. saxatilis Grown in Cages

Abstract.— In an effort to feed sunshine bass Morone chrysops×M. saxatilis efficiently, promote optimal growth, and reduce labor costs associated with feeding, sunshine bass were grown in cages and fed one of four feeding frequencies: once/d, twice/d, once every other day (I X/EOD), and twice every other day (2X/EOD) for 21 wk. Juvenile sunshine bass were fed a commercial floating diet containing 40% protein and 11.5% lipid. One hundred fish were hand‐counted and stocked into each of 12 3.5‐m3 cages with three replications per treatment. At the conclusion of the study, percentage weight gain of sunshine bass fed twice/d was significantly (P < 0.05) higher (1,850%) compared to fish fed all other feeding frequencies. Specific growth rate (SGR) of fish fed twice/d was significantly higher (2.1%/d) compared to fish fed all other feeding regimes, while fish fed once/d had a higher SGR (2.0%/d) compared to fish fed I X/EOD (1.6%/d) and 2X/EOD (1.8%/d). Percentage survival was not significantly different (P > 0.05) among all treatments and averaged 70.4%r. Feed conversion ratio (FCR) of fish fed twice/d was significantly higher (2.40) compared to fish fed all other feeding regimes. Percentage fillet weight of fish fed twice/d was significantly higher (27.8%) compared to all other treatments. Percentage moisture, protein, lipid, and ash in fillet were not significantly different among all treatments and averaged 75.7%, 19.4%, 3.5%, and 1.2%n, respectively (wet‐weight basis). Based upon data from the present study, it appears that producers growing juvenile sunshine bass in cages may want to feed fish twice daily. This feeding regimen allows for higher growth rates, without adverse effects on body or fillet compositions. However, economic analysis needs to be conducted to determine if feeding twice/d is profitable.

Evaluation of Corn Gluten Feed as a Dietary Ingredient for Pond‐Raised Channel Catfish Ictalurus punctatus

Abstract.— This study was conducted to evaluate corn gluten feed as an alternative feedstuff in the diet of pond‐raised channel catfish Ictalurus punctatus. Three 32%‐protein diets containing 0%, 25%, or 50% corn gluten feed were tested. Channel catfish fingerlings (average weight: 57 g/fish) were stocked into 15 0.04‐ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed to satiation once daily for a 147‐d growing period. No differences were observed in feed consumption, weight gain, feed conversion ratio, survival, or fillet protein concentration among fish fed the test diets. Fish fed diets containing 25% and 50% corn gluten feed exhibited a lower level of visceral fat and a higher carcass yield than fish fed the control diet without corn gluten feed. The diet containing 50% corn gluten feed resulted in a lower level of fillet fat and a higher level of moisture than the control diet. There were no visible differences in the coloration of skin or fillet of channel catfish fed diets with and without corn gluten feed. Results from this study indicated that channel catfish can efficiently utilize corn gluten feed at levels up to 50%n without adverse effect on feed palatability, weight gain, or feed efficiency. Corn gluten feed may be beneficial in reducing fattiness of channel catfish and improving carcass yield by reducing the digestible energy to protein ratio of the diet.

Evaluation of Various Concentrations of Dietary Protein and Animal Protein for Pond‐Raised Channel Catfish Ictalurus punctatus Fed to Satiation or at a Restricted Rate

AbstractA factorial experiment was conducted to evaluate effect of dietary protein (28% or 32%), animal protein (0, 3, or 6%), and feeding rate (satiation or >90 kg/ha per d) on production characteristics, processing yield, and body composition of pond‐raised channel catfish Ictalurus punctatus. Fingerling channel catfish (average weight: 55 g/fish) were stocked into 60, 0.04‐ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed once daily to satiation or no more than 90 kg/ha per d for 147 d. Fish fed at a rate of >90 kg/ha per d consumed about 85% of the amount of feed consumed by fish fed to satiation. Dietary protein did not affect the total amount of feed fed, amount of feed consumed per fish, weight gain, feed conversion efficiency, or fillet protein. Animal protein had no effect on the total amount of feed fed, amount of feed consumed per fish, weight gain, or fillet protein and ash. Fish fed a diet containing 6% animal protein converted feed more efficiently than fish fed diets containing 0% and 3% animal protein. Fish fed to satiation daily consumed more feed, gained more weight, converted the feed less efficiently, and had a higher carcass yield, a higher level of visceral fat as compared to fish fed at a rate of >90 kg/ha per d. Feeding rate had no effect on fillet protein. Results from this study indicated that both a 28% and a 32% protein diet with or without animal protein provided the same growth rate of channel catfish raised in ponds from fingerlings to marketable size if feed is not restricted below a maximum rate of 90 kg/ha per d. Even though there were some interactions among the three factors evaluated, dietary protein levels of 28% to 32% and animal protein levels of 0% to 6% do not appear to markedly affect carcass yield and fillet proximate composition of pond‐raised channel catfish.

Effects of Different Feeding Frequencies on Growth, Body Composition, and Fillet Composition of Juvenile Sunshine Bass, Morone chrysops × M. saxatilis Grown Indoors

In an effort to feed sunshine bass (Morone chrysops X M. saxatilis) efficiently, promote optimal growth, and reduce labor costs associated with feeding, sunshine bass were fed one of four feeding schedules: once per day, twice per day, once every other day, and twice every other day for 10 weeks. Ten fish were stocked into each of sixteen 110-L aquaria with four replications per treatment. At the conclusion of the feeding trial, percentage weight gain of sunshine bass fed twice/day were significantly (P < 0.05) higher (342%) compared to fish fed all other feeding frequencies. Specific growth rate (SGR) of fish fed twice/day was significantly higher (1.85%/day) compared to fish fed once every other day (0.69%/day) and twice every other day (1.18%/day) but not different (P > 0.05) from fish fed once/day (1.51%/day). The amount of diet consumed by fish fed twice/day was significantly higher (119 g diet/fish) compared to fish fed all other feeding frequencies. Feed conversion ratio (FCR) of fish fed twice/day were significantly higher (1.50) compared to fish fed once/day (1.28) and once every other day (1.15) but not different (P > 0.05) from fish fed twice every other day (1.35). Percentage fillet weight of fish fed once/day and twice/day were significantly higher (20.3% and 21.2%, respectively) compared to fish fed once every other day (15.7%) but not different from fish fed twice every other day (18.8%). Percentage lipid in fillet was not significantly different among all other treatments and averaged 9.7%. Percentage protein in fillet of fish fed once every other day and twice every other day was significantly (P > 0.05) higher (90% and 82.1%, respectively) compared to fish fed once/day and twice/day (81.1% and 81.5%, respectively). Based upon data from the present study, it appears that producers growing small juvenile sunshine bass indoors should feed fish twice daily. This feeding regimen allows for higher growth rates, without adverse effects on body or fillet compositions.

Manipulation of end-product quality of rainbow trout with finishing diets

The effect of dietary lipid level upon various quality parameters of smoked rainbow trout were examined. Fish were fed four experimental diets differing in lipid content (18.8–31.4%). Groups received either a lipid-rich diet throughout the trial (101 days), a lipid-rich feed for 46 days followed by a lower fat diet for 55 days and vice versa, or a low fat diet throughout. A fifth group (controls), consisting of commercially reared animals, was employed for comparative purposes. The visceral fraction of experimental fish increased with increasing lipid ingestion, whereas final process yield decreased. Chemical analyses following salting and hot-smoking revealed that fillet lipid and ash was higher (P < 0.05) and moisture lower (P < 0.05) for fish fed the high-lipid diet throughout and during the last 55 days of trial. No differences were recorded with respect to sensory attributes between treatment groups, although differences were observed between tank-reared and control fish. In experimental animals, fillet protein content was negatively correlated with juiciness and fibreness, while dry matter was correlated with juiciness, fresh oily taste and rose flesh colour. The present study indicates that high lipid feeds can be employed without negatively influencing sensory characteristics or yield provided that lean finishing diets are fed prior to slaughter. Fasting of fish for 61 days improved slaughter yields without affecting relative yields among dietary groups.

Effect of Dietary Protein Concentration and Feeding Rate on Weight Gain, Feed Efficiency, and Body Composition of Pond‐Raised Channel Catfish Ictalurus punctatus1

AbstractTwo experiments were conducted in earthen ponds to evaluate the effect of dietary protein concentration and feeding rate on weight gain, feed efficiency, and body composition of channel catfish. In Experiment 1, two dietary protein concentrations (28% or 32%) and four feeding rates (≤ 90. ≤ 112, ≤ 135 kg/ha per d, or satiation) were used in a factorial arrangement. Channel catfish Ictalurus punctatus fingerlings (average size: 27 g/fish) were stocked into 0.04‐ha ponds at a rate of 24,700 fish/ha. Fish were fed once daily at the predetermined maximum feeding rates for 282 d (two growing seasons). In Experiment 2, three dietary protein concentrations (24, 28, or 32%) and two feeding rates (≤ 135 kg/ha per d or satiation) were used. Channel catfish (average size: 373 g/fish) were stocked into 0.04‐ha ponds at a rate of 17,300 fish/ha. Fish were fed once daily for 155 d. In both experiments, five ponds were used for each dietary treatment. Results from Experiment 1 showed no differences in total feed fed, feed consumption per fish, weight gain, feed conversion ratio (FCR), or survival between fish fed diets containing 28% and 32% protein diets. As maximum feeding rate increased, total feed fed, feed consumption per fish, and weight gain increased. There were no differences in total feed fed, feed consumption per fish, or weight gain between fish fed at ≤ 135 kg/ha per d and those fed to satiation. Fish fed the 28% protein diet had a lower percentage carcass dressout and higher percentage visceral fat than fish fed the 32% protein diet. Dietary protein concentrations of 28% or 32% had no effect on fillet protein, fat, moisture, and ash. Feeding rate did not affect FCR, survival, percentage carcass dressout, or fillet composition, except fillet fat. As feeding rate increased, percentage visceral fat increased. Fish fed at ≤ 90 kg/ha per d had a lower percentage fillet fat than fish fed at higher feeding rates. In Experiment 2, dietary protein concentration or maximum feeding rate did not affect total feed fed, feed consumption per fish, weight gain, FCR, or survival of channel catfish. Feeding rate had no effect on percentage carcass dressout and visceral fat, or fillet composition. This was due to the similar feed consumption by the fish fed at the two feeding rates. Fish fed the 24% protein diet had lower carcass dressout, higher visceral fat and fillet fat than those fed the 28% or 32% protein diet. Results from the present study indicate that both 28% and 32% protein diets provide satisfactory fish production, dressed yield, and body composition characteristics for pond‐raised channel catfish fed a maximum rate of 90 kg/ha per d or ahove.

Feed ration prior to slaughter—a potential tool for managing product quality of Atlantic salmon ( Salmo salar)

During a 110-day winter period, five duplicated groups of 50 Atlantic salmon (3.9 kg initial weight) were fed 0.0, 0.25, 0.5, 0.75 and 1.0 times maximum feed intake before slaughter with the purpose of studying body composition and quality related characteristics in raw and smoked salmon fillets. Final weights increased linearly with feed ration from 3.5 to 4.9 kg at ration 0.0 and 1.0, respectively. Decreasing feed ration resulted in a slimmer body shape (i.e., lower condition factor), increased carcass-yield and decreased fillet-yield, and decreased fillet fat content. Although fillet protein content was not significantly affected by ration level, the percent of water-soluble proteins in white muscle was increased by feed ration. Decreased content of free and increased content of protein-bound hydroxyproline in white muscle was found with increasing feed ration. White muscle pH, in post-rigor state, but not at slaughter, decreased with increasing ration level, reflecting in vivo glycogen and post-rigor lactate levels. After filleting, a significant increase of fillet gaping was found with increasing ration. Sensory analyses of smoked fillets revealed that fatness, juiciness and coarseness increased, whereas hardness decreased with increasing feed ration. Further, acidulous flavour and odour in smoked fillet increased significantly. Despite an increased astaxanthin content in raw fillet, the sensory scores for colour intensity decreased and whiteness increased with increasing feed ration. Consequently, reduced ration before slaughter can be a tool for improving slaughter-yield, reducing fat content and gaping in raw fillet, slightly improving colour intensity and changing textural properties of smoked fillet. The costs in terms of lost weight and less fillet-yield will, however, be substantial.

Evaluation of Practical Diets with Various Levels of Dietary Protein and Animal Protein for Pond‐Raised Channel Catfish Ictalurus punctatus1

AbstractThree levels of dietary protein (26, 28, or 32%) and four levels of animal protein (0, 2, 4, or 6%) were evaluated in a factorial experiment for pond‐raised channel caffish using practical‐type extruded feeds. Meat, bone, and blood meal (65% protein) was used as the animal protein source. Channel catfish fingerlings (average weight: 69 glfish) were stocked into 48 0.04‐ha ponds at a rate of 24,700 fishha. Four ponds were used for each dietary treatment. Fish were fed once daily to apparent satiation for 158 d. No differences were observed in weight gain, feed consumption, feed conversion ratio, survival, and hematocrits of channel catfish fed diets containing various levels of dietary protein and animal protein. Inclusion of animal protein in the diet did not affect fish dressout, percentage visceral fat, or fillet composition. Comparison of means pooled by dietary protein without regard to animal protein showed that fish fed diets containing 26% protein had a lower percentage dressout than fish fed higher protein diets (55.4% vs. 56.3%). Fish fed the 32% protein diet had lower visceral fat than those fed the 26% or 28% protein diet (2.9% vs. 3.6% or 3.4%). Fillet fat was lower for fish fed the 32% protein diet than for fish fed the 26% protein diet (5.8% vs. 7.1%). Fillet fat in fish fed the 28% protein diet (6.5%) was not different from fish fed either 26% or 32% dietary protein. No differences were detected in fillet protein, moisture, and ash concentrations among fish fed diets containing various concentrations of protein. There were no interactions between dietary protein and animal protein for any variables. Results from the present study indicate that animal protein can be eliminated from diets for grow out of channel catfish fed to apparent satiation using diets containing 26% to 32% crude protein.

Effect of Reducing Dietary Digestible Energy to Protein Ratio on Weight Gain and Body Fat of Juvenile Channel Catfish Ictalurus punctatus1

Abstract.A laboratory feeding trial was conducted to evaluate the effects of reducing digestible energy to protein (DE:P) ratios of practical diets on body fat and weight gain of channel catfish. Five diets were formulated to contain 32, 28, or 24% crude protein with typical DE:P ratios of 8.5, 9.9, or 11.4 kcal/g protein, respectively, and 28% or 24% protein with a reduced DE:P ratio of 8.5 kcal/g protein. Cellulose was used to adjust the DE:P ratio. Juvenile channel catfish Ictalurus punctatus (initial weight: 5.2 g/fish) were fed the experimental diets twice daily to apparent satiation for 12 wk. Fish fed the 28% protein diet with a reduced DE:P ratio of 8.5 kcal/g protein gained less weight and converted feed less efficiently than those fed the 28% protein diet with a typical DE:P ratio of 9.9 kcal/g protein. Fish fed the 24% protein diet with a reduced DE:P ratio of 8.5 kcal/g protein had a similar weight gain but converted feed less efficiently than those fed the 24% protein diet with a typical DE:P ratio of 11.4 kcal/g protein. Weight gain and feed conversion efficiency of fish fed the 32% protein diet with a typical DE:P ratio of 8.5 kcal/g protein were higher than for fish fed other diets except those fed the 28% protein diet with a DE:P ratio of 9.9 kcal/g protein. There were no differences in feed consumption and survival among dietary treatments. Fillet fat of fish fed the 24% and 28% protein diets with a reduced DE:P ratio was lower than that of the fish fed diets containing the same protein concentrations with typical DE:P ratios. At a DE:P ratio of 8.5 kcal/g protein, there were no differences in fillet fat concentration among fish fed diets containing different protein concentrations. There were no differences in fillet protein, moisture, and ash between fish fed the 24% or 28% protein diets containing reduced and typical DE:P ratios. Results from this study show that reducing DE:P ratios in practical diets lowers body fat but also depresses weight gain of channel catfish; thus it would not be economical to use this strategy to reduce body fat of the fish.

Comparison of Practical Diets with and without Animal Protein at Various Concentrations of Dietary Protein on Performance of Channel Catfish Ictalurus punctatus Raised in Earthen Ponds1

Abstract— A 2 × 5 factorial experiment was conducted using practical‐type extruded feeds containing 20, 24, 28, 32, or 36% crude protein with or without animal protein. The animal protein supplement consisted of 4% menhaden fish meal and 4% meat, bone and blood meal. Channel catfish fingerlings (average size: 26.3 g/fish) were stocked into 50 0.04‐ha ponds at a rate of 24,700 fishha. Five ponds were used for each dietary treatment. Fish were fed once daily to satiation for 202 d. There were no differences in feed conversion ratio (FCR), percentage fillet moisture, and survival among treatments. In fish fed diets containing no animal protein, feed consumption, weight gain, and percentage dressout were lower for fish fed the 20% protein diet than those fed diets containing 28% and 32% protein. Fish fed 28, 32, or 36% protein diets without animal protein did not differ in respect to percentage dressout and percentage visceral fat; fish fed the 36% protein diet had higher percentage fillet protein and a lower percentage fillet fat than fish fed other diets with the exception of fish fed the 28% protein diet. In fish fed diets containing animal protein, feed consumption, weight gain, percentage fillet protein and ash, and percentage dressout were lower and visceral fat was higher for fish fed the 20% protein diet than those fed other diets. Fish fed diets containing 24% protein and above with animal protein were not different in respect to weight gain and feed consumption, but fish fed the 24% protein diet had a higher percentage fillet fat than fish fed a 32% or 36% protein diet. Fish fed the 32% protein diet had a lower visceral fat. Considering animal protein vs non‐animal protein with the data pooled across all diets without regard to dietary protein level, weight gain and FCR of fish fed diets containing animal protein were higher than those fed diets containing no animal protein. However, weight gain of fish fed diets containing 20, 28, or 32% protein with or without animal protein did not differ. Dressout percentage and fillet protein were higher and fillet fat was lower for fish fed diets containing no animal protein than those fed diets containing animal protein. Data from this study indicated that animal protein may not be a necessary dietary ingredient for fish fed 28% or 32% protein diets typically used for grow out of pond‐raised channel catfish under satiation feeding conditions. Whether animal protein should be included in catfish diets containing less than 28% protein is unclear, since fish fed the 24% protein diet benefited from animal protein but those fed the 20% protein diet did not benefit from animal protein. Additional studies to provide more information on low‐protein, all‐plant diets are currently being conducted.

Application of near-infrared transmittance spectroscopy in the determination of fat, protein and dry matter in Atlantic halibut fillet

Near infrared transmittance (NIT) spectroscopy (850–1048 nm) has been applied to the measurement of fat, protein and dry matter in wet homogenized Atlantic halibut ( Hippoglossus hippoglossus) fillet. A total of 155 fillet cuts (five sample sites) were selected from the start of the investigation (survey I) and 98 fillet cuts (one sample site) were also selected from eight fish groups six months later (survey II). The fish groups originated from a slaughtering quality experiment, where fish size and fat content in the feed had been varied. The multivariate calibration models were tested separately for each survey and after mixing the survey samples. The models were also tested after inclusion of sample temperature or fish weight, or after reduction to spectra of eight wavelengths. The selected fillet cuts from survey II gave calibration models with the best prediction abilities for fat and dry matter, whereas the combination of samples from both surveys gave the best prediction abilities for protein. The constituent ranges (w.w.) were: 10–123 g/kg fat, 165–274 g/kg protein and 234–335 g/kg dry matter. The partial least squares regression resulted in the following prediction errors, expressed as root-mean-square error of cross validation: 2.7 g/kg fat, 5.2 g/kg protein and 4.2 g/kg dry matter. The temperature adjustment had positive influence on the test set validation of protein and dry matter, whereas the fish-weight adjustment had positive influence on the test set validation of fat. Calibration models based on eight wavelengths were not optimal, but showed promising results, applicable in a simpler instrument for future online quality monitoring of Atlantic halibut fillet.

Starvation prior to slaughter in Atlantic salmon ( Salmo salar) : I. Effects on weight loss, body shape, slaughter- and fillet-yield, proximate and fatty acid composition

During an 86-day winter period, triplicate groups of 20 Atlantic salmon weighing ca. 5 kg were fed a high-energy diet and subsequently starved for 0, 3, 7, 14, 30, 58 and 86 days prior to slaughter. Length, whole body and organ weights were recorded. Gutted fish were subjected to evaluation of visual fatness and X-ray computer tomography evaluation of body shape and visual fat deposits. Proximate and fatty acid analyses were performed on liver, viscera, and different fillet segments. Starvation for 86 days resulted in an 11.3% weight loss, whereas fish fed during the same period showed a 26.3% weight gain. The rate of weight loss was diminished with increasing starvation time. A systematic leaner body shape was documented by decreases in visual fatness score, condition factor and in the ratios of the cross-sectional height, width and area to fork length with increasing starvation time. Slaughter yield increased systematically up to 30 days of starvation, whereas fillet yield decreased after 58 and 86 days starvation. Fillet fat content was slightly lower after 58 and 86 days of starvation compared with normally fed fish. Predicted visual fat deposits (by X-ray tomography) were not significantly affected by starvation time. Independent of starvation time, a high variation in fat content was found among different fillet segments. The fillet protein content was higher in fed fish (0 days starvation) than in fish starved for 86 days. Some significant, but marginal differences in the fatty acid composition of muscle, belly flap and liver between fed and starved fish were observed. Both protein and fat were important sources of energy during starvation. Fillet was used most, followed by viscera and liver. Long-term starvation at winter temperatures seem to produce only marginal changes in body composition of big Atlantic salmon, but rather a shrinkage of the total body mass as illustrated by weight loss, less fillet-yield and a leaner body shape in starved fish.

Evaluation of Three Strains of Channel Catfish Ictalurus punctatus Fed Diets Containing Three Concentrations of Protein and Digestible Energy1

Abstract A 3 × 3 factorial experiment was conducted using three strains of channel catfish Ictalurus punctatus, USDA102, USDA103, and Mississippi normal (MN), and three concentrations of dietary protein. Three practical diets were formulated to contain 25, 35, or 45% crude protein with digestible energy/protein ratio of 10.0, 8.1, or 6.8 Kcal/g, respectively. Juvenile channel catfish (mean initial weight: 15.1 g/fish) were fed the experimental diets twice daily to approximate satiation for 8 wk. Regardless of dietary protein concentration, the USDA 103 strain consumed more feed, gained more weight, and converted feed more efficiently than other two strains. The MN strain consumed less feed and gained less weight than the other strains. Regardless of the strain of channel catfish, differences in weight gain, feed consumption, and feed conversion ratio were observed among fish fed diets containing various levels of protein with the 35% protein diet being the best. Neither dietary protein concentration nor strain had significant effect on fillet protein level. Data pooled by fish strain showed that fish of MN strain had lower fillet fat and higher moisture than fish of other two strains. Data pooled by dietary protein showed that fish fed the 45% protein diet had a lower level of fillet fat than fish fed the 35% protein diet, but this did not appear to be a strain effect, rather it was a result of decreased feed consumption. Results from this study clearly demonstrate that per formance of the USDA103 strain of channel catfish was superior to other strains tested. The growth characteristics of the USDA103 strain of channel catfish make the strain a promising candidate for commercialization. However, data are needed on performance of the strain from fingerling to marketable size under conditions similar to those used for the commercial culture of channel catfish prior to their release to the catfish industry.

Growth, feed conversion, fillet proximate composition and resistance to Edwardsiella ictaluri of channel catfish, Ictalurus punctatus (Rafinesque), blue catfish, Ictalurus furcatus (Lesueur), and their reciprocal F1 hybrids fed 25% and 45% protein diets

Juvenile channel catfish, Ictalurus punctatus (Rafinesque), blue catfish, I. furcatus (Lesueur), and their reciprocal Fl hybrids were fed practical diets containing 25% and 45% protein during a 10-week trial to determine the effects of genotype, dietary protein level and genotype X diet interactions on growth, feed conversion ratio (FCR), fillet proximate composition and resistance to the bacterium Edwardsiella ictaluri. Rankings of genotypes (best to worst) for absolute weight gain, percentage weight gain and FCR were: channel, channel female X blue male, blue, and blue female X channel male for the 25% protein diet; and channel, channel X blue, blue X channel, and blue for the 45% diet. Diet did not affect growth or FCR of channel catfish, but growth and FCR were better for blue catfish and both hybrids fed the 25% diet compared to those fed the 45% diet. Channel catfish additive genetic and maternal effects were favourable, and heterosis was negative for growth and FCR. After adjusting for effects of fish size, genotype had no effect on fillet composition. Fillet protein was higher for all genotypes, and fillet lipid was lower for blue catfish and hybrids fed the 45% diet than for fish fed the 25% diet. Genotype X diet interactions observed for growth, FCR and fillet lipid appeared to be a result of poor palatability of the 45% diet to blue catfish and hybrids. Survival (76-93%) and antibody levels (0.10-0.24 OD) after exposure to E. ictaluri at the end of the feeding trial were not affected by genotype or diet. Hybridization of blue catfish and channel catfish would not be an effective method for improving the traits measured for the fish strains and diets used in this study.

Effects of supplemental lysine and methionine in low protein diets on weight gain and body composition of young channel catfish Ictalurus punctatus

Two experiments were conducted to evaluate the effects of supplementation with lysine, methionine, or both in low protein but amino acid (AA)-replete diets on weight gain and body composition of channel catfish (mean initial weight: 10–11.9 g/fish) raised under laboratory conditions. In experiment 1, a 2×3 factorial arrangement with two feeding rates (approximately 75 and 100% satiation) and three test diets was used. Diets 1 and 2 were formulated to contain 32 and 24% crude protein, respectively. Diet 3 was the same as diet 2 except that 0.4% supplemental lysine was added. Fish were fed once daily for 12 weeks. In experiment 2, a 2×4 factorial arrangement with two dietary protein levels (24 or 28%) and four AA supplements was used. Lysine, methionine, or both were supplemented to the basal diets to bring the level of these two essential AAs to 30% above the requirement for channel catfish. Fish were fed once daily to approximate satiation for 12 weeks. In both experiments, five aquaria were used in each dietary treatment. In experiment 1, regardless of feeding rate, fish fed diets containing 24% protein with or without supplemental lysine gained less weight and converted feed less efficiently than fish fed the 32% protein diet. There were no differences in weight gain between fish fed the 24% protein diets with and without supplemental lysine. Feed efficiency of fish fed the 24% protein diet with supplemental lysine was higher than that of fish fed the diet without supplemental lysine. Fillet fat of fish fed diets containing 24% protein with or without supplemental lysine was greater than that of fish fed the 32% protein diet. There were no differences in fillet fat between fish fed the 24% protein diets with and without supplemental lysine. Fillet protein was not affected by diet or feeding rate. In experiment 2, regardless of dietary protein concentration, no significant differences were observed in weight gain, feed consumption, feed efficiency, or fillet composition among fish fed diets with or without supplemental AAs. Results from this study indicate that supplementation with lysine and/or methionine in low protein but AA-replete diets is not beneficial for channel catfish.

Low Protein Diets for Channel Catfish Ictalurus punctatus Raised in Earthen Ponds at High Density1

AbstractThis study was conducted to evaluate the use of low protein diets for channel catfish Ictalurus punctatus raised in earthen ponds at high density. Fingerling channel catfish were stocked into 0.04‐ha earthen ponds at a rate 24,700 fish/ha and fed experimental diets daily to satiation from April to October 1995. The five diets contained either 32, 28, 24, 20, or 16% crude protein with digestible energy to protein (DE:P) ratios ranging from 8.9 to 16.2 kcal/ g protein. Weight gain was not different among channel catfish fed diets containing 32, 28, or 24% crude protein. Fish fed diets containing 20% or 16% crude protein gained less weight than fish fed the diets containing 28% or 24% crude protein, but not statistically less than the fish fed the 32% crude protein diet. Feed consumption data followed similar trends as weight gain data. Feed conversion ratio increased linearly as dietary protein decreased, but was not significantly different (multiple range test) for fish fed diets containing either 32% or 28% crude protein. There were no differences in survival and hematocrit of fish fed the different diets. No differences (multiple range test) were observed in dressout percentages for fish fed the various diets, but dressout percentage tended to decrease linearly as dietary protein decreased. Visceral fat and fillet fat increased and fillet protein and moisture decreased linearly as dietary protein decreased. Results from this study indicated that dietary protein concentrations as low as 24% are adequate for maximum weight gain of pond‐raised channel catfish fed daily to satiation. Fish fed dietary protein levels below 24% grew relatively well, particularly considering that dietary protein was reduced 40–50% below that typically used in commercial channel catfish feeds. However, dietary protein levels below 24% may increase fattiness to an unacceptable level presumably because of the high digestible energy to protein ratio.

Effects of Replacing Fish Meal in Diets on Growth and Body Composition of Palmetto Bass (Morone saxatilis × M. chrysops) Raised in Cages

ABSTRACT Juvenile palmetto bass (Morone saxatilis X M. chrysops) with an average weight of 20 g were stocked into 12 floating cages (1.2 × 1.2 × 2.4 m) and fed one of four practical diets formulated to contain various percentages (0,15, 30, or 45%) offish meal (FM). Diets were formulated to be isonitrogenous (43% protein) and isocaloric (3.9 kcal available energy/g). Fish were fed twice daily, all they would consume in 40 minutes (0900 and 1730), for 125 days. Final individual weight and specific growth rate (SGR) of fish fed diets containing 15, 30, or 45% fish meal were not significantly different (P > 0.05) and averaged 342 g and 2.3%/day, while growth of palmetto bass fed a diet containing soybean meal (SBM), and meat-and-bone meal, without FM, was significantly (P <0.05) lower (282 g and 2.1%/day). There were no significant differences (P >0.05) in percentage moisture, protein, and lipid in fillet from palmetto bass in the four treatments, of which these values averaged 75.1%, 80.7%, and 14.5%, respectively. Amino acid composition of fillets was similar among treatments. These data suggest that a diet containing 15% FM is sufficient for diet palatabiiity and good growth in juvenile palmetto bass. Additional research on diet formulations without FM should be conducted.

Non‐destructive determination of fat, moisture and protein in salmon fillets by use of near‐infrared diffuse spectroscopy

AbstractNear infrared (NIR) diffuse spectroscopy was used to determine the fat, moisture and protein contents in whole and ground farmed atlantic salmon fillets. A remote fibre‐optic probe was used for NIR measurements on 50 whole salmon fillets. The constituent ranges were: 91‐205 g kg−1 fat, 599‐709g kg−1 moisture and 186‐209 g kg−1 protein. Principal component regression resulted in the following prediction errors for ground salmon fillets, expressed as root mean square error of cross validation: 6.6 g kg‐1 fat, 3.8 g kg−1 moisture and 2.0 g kg−1 protein. The corresponding prediction errors for non‐destructive measurements on whole salmon fillets were 10.8 g kg−1 fat, 8.5 g kg−1 moisture and 3.7 g kg−1 protein. Regression models using the 760‐1100 m range gave lower prediction errors than models using the 1100‐2500 mm or 760‐2500 nm ranges. The results show that fibre‐optic probe NIR instruments are suited to determine fat and moisture in whole salmon fillets non‐destructively.

Partial characterization and nutritive value of proteins from pacu (Colossoma mitrei, Berg 1895)

The edible portion (fillet) of pacu (Colossoma mitrei), a freshwater fish from the south of Brazil, was composed of 67.7% water, 13% protein, 17.2% total lipids, and 1.3% minerals. The muscle proteins were composed of 64.3% myofibrillar, 25% sarcoplasmic, and 8% stroma proteins. Simple polyacrylamide gel electrophoresis revealed six protein bands in the sarcoplasmic fraction; SDS-polyacrylamide gel electrophoresis revealed eight protein structural units with molecular weights ranging from 4000 to 149 000. Total protein nutritive value was similar to that of casein in terms of PER and growth-promoting capacity. Full-fat fillet protein did not differ from casein (p = 0.05) with respect to apparent digestibility and net protein utilization but was inferior to casein in the apparent biological value. On the other hand, defatted fillet protein was inferior to casein (p = 0.05) in all of the three indices calculated.

Oxidation of methionine. Effects of hydrogen peroxide alone and in combination with iodide and selenite

The oxidation of methionine by hydrogen peroxide, and the influence of iodide, pH, amino acids and selenite were studied with free methionine and with casein and fish fillet protein. The concentration levels tested ranged from 0·05 m m to 3·0 m m . Hydrogen peroxide oxidation was not influenced by pH in the range 5·0 to 8·0; at pH 8·5 the rate of oxidation was increased. When iodide was added in amounts equivalent to or less than the amounts of H 2O 2, the reaction was accelerated with free but not protein-bound methionine. At higher levels iodide inhibited the oxidation. An amino acid mixture and proteins inhibited the effect of iodide; this effect seemed to be due to tryptophan. Selenite also accelerated the effect of H 2O 2, both with free and with protein-bound methionine. Cu ++ catalysed the oxidation by H 2O 2 at low reactant concentration but not at the higher levels. The reaction between methionine and H 2O 2 seemed to be of first order with respect to both reactants.