Evaluation of Decapsulated Artemia Cysts in Hatchery Diets for Channel Catfish Ictalurus punctatus Fry and Effects on Subsequent Fingerling Production

Abstract.— Two 10-d hatchery growth trials were conducted to determine if differences in growth, body composition, and survival existed among catfish fry Ictalurus punctatus fed a diet of 100% catfish-starter (CS) or CS in combination with decapsulated Artemia cysts (DAC) at 25%, 50 % , or 75% of diet weight. A 120–d production trial was undertaken immediately following the first hatchery trial to evaluate the effects of diet on production characteristics (survival, length, weight, feed conversion ratio, and total yield) of fingerling catfish produced from hatchery-raised fry. Fry fed diets containing DAC weighed 61–98% more ( P < 0.05) than fry fed only CS. The size differential of DAC-fed fry was maintained through 120 d of growth in simulated nursery ponds (0.001-ha earthen-bottom pools). The increased growth of fry fed DAC might have been related to differences in dietary lipid content, amino acid composition, or digestibility of CS and DAC. Body weights of fingerlings produced under simulated production conditions from fry fed hatchery diets containing 50% and 75% DAC were 17% and 25% higher, respectively, 130 d post-hatch, than fingerlings produced from fry fed only CS. In addition, the total yield of fingerlings produced from fry fed 75% DAC was 17% greater that that of fingerlings produced from fry fed only CS. The increased performance of fingerlings produced from DAC-fed fry could have resulted from their larger size at stocking, since larger fry might be capable of capturing natural food organisms and ingesting prepared diets more effectively than smaller fish. CS-DAC diet combinations could be used to increase weight gain of hatchery-raised fry if the cost-benefit ratio of adding DAC to the standard hatchery diet warrants its use.     

The Use of Decapsulated Cysts of the Brine Shrimp Artemia as Direct Food for Carp Cyprinus carpio L. Larvae

Decapsulated Arremia cysts have been evaluated as a direct food source for larvae of the carp Cyprinus carpio L. All decapsulated cyst diets gave excellent survival of carp larvae during the first two weeks of culturing. Unlike traditionally brine-stored decapsulated cysts, dried Artemia embryos provided growth results comparable to those obtained with freshly hatched Artemia nauplii. Furthermore, except for Artemia embryos that lost their hatchability after long-term storage in air, several other inactivation treatments, simulating improper harvesting and processing of cysts, did not produce a significant decrease in the nutritional quality of the decapsulated cysts.
Using decapsulated cysts 89 a direct food source for carp larvae, instead of nauplii, the quantity of cysts needed can be reduced by about 25% to 35% after one and two weeks of culturing, respectively. Moreover, the use of decapsulated cysts advances the possible commercialition of poor-hatching and less expensive cyst products for culture of carp larvae.     

A Comparative Study on the Use of Different Preparations of Decapsulated Artemia Cysts as Food for Rearing African Catfish (Clarias gariepinus) Larvae

African catfish ( Clarias gariepinus ) larvae were fed on five preparations of decapsulated Great Salt Lake Artemia cysts: 1) dried (35C, 6h) and UV-irradiated cysts; 2) heated cysts (80C, 10 min); 3) brinedehydrated and UV-irradiated cysts; 4) micro-bound diet 1 (with intact decapsulated cysts used in diet preparation 1); and 5) micro-bound diet 2 (with crushed and shited decapsulated cysts used in diet preparation 1). The larvae were fed from the first day after yolk-sac resorption (fourth day after hatching). After a 14-d rearing period, larvae fed on dried or heated decapsulated cysts yielded significantly higher mean weights than the groups fed on brine-dehydrated decapsulated cysts or micro-bound diet 1. Feeding micro-bound diet 2 resulted in a significantly lower average gain in weight as compared to the other groups.     

Evaluation of Coastal Bermuda Grass Protein Isolate as a Substitute for Fishmeal in Practical Diets for Channel Catfish Ictalurus punctatus

In response to concerns over availability and cost of fishmeal for aquaculture feeds, a study was conducted to evaluate the suitability of a protein isolate from coastal Bermuda grass Cynodon dactylon for channel catfish Ictalurus punctatus . The coastal Bermuda grass was treated by soaking in liquid anhydrous ammonia under high pressure at 70 C, a process known as Ammonia Fiber Explosion (AFEX), followed by pressure release, extraction and isoelectric precipitation for isolation of the protein. Amino acid analysis of the isolate (32% crude protein) indicated a generally balanced profile that was first limiting in methionine. A feeding trial was conducted in which four isonitrogenous and isocaloric diets containing incremental levels of the extracted, isolated protein were evaluated. The control diet contained 10% menhaden fishmeal and experimental diets were formulated so that the isolate replaced 33, 66 and 100% of the fishmeal on an equal-protein basis. Each diet was fed for 9 wk to triplicate groups of channel catfish fingerlings initially weighing approximately 14 g/fish. Apparent protein and organic matter digestibility of the isolate also was determined utilizing chromic oxide as an inert marker. Results of the feeding trial indicated that substitution of the isolate at all levels did not significantly ( P > 0.05) affect weight gain, feed efficiency, protein efficiency ratio or protein retention of channel catfish. Apparent protein and organic matter digestibility coeflicients of the isolate were 85 and 89%, respectively. These data indicate that the isolate was readily digested by channel catfish and was able to replace menhaden fishmeal (at 10% of diet) without adversely affecting fish performance. Additional research to evaluate substitution of other ingredients with the protein isolate appear warranted. Further research to optimize protein isolation procedures also is required.     

Evaluation of Alternative Protein Sources to Replace Fish Meal in Practical Diets for Juvenile Tilapia,Oreochromis spp

Two feeding experiments were conducted to evaluate if methionine is limiting in practical grow‐out diets for tilapia, Oreochromis spp. Four diets containing 32% protein and 5% lipid were designed to compare the use of diets high in dehulled solvent‐extracted soybean meal (DSESM) and expeller pressed soybean meal (EPSM) compared with a diet containing 6% fish meal (FM). Tilapia (4.78 ± 0.07 g, mean ± SD) were randomly stocked into twelve 600‐L flow‐through tanks at 20 fish per tank. After 6 wk, there were no notable trends or statistically significant differences (P > 0.05) in final mean weight, survival rate, and feed conversion ratio (FCR) among the treatments. Because results of this study indicated that DSESM could totally replace FM in practical diets for juvenile tilapia, a second batch of diets were formulated using other protein sources. Typical levels of cottonseed meal (CSM), DSESM, and meat and bone meal (MBM) were used to evaluate whether methionine could be limiting. Two basal diet formulations were tested either without or with methionine supplement (0.06/100 g diet). The first diet contained 15% CSM, 27% DSESM, and 10% MBM and the second diet contained 15% CSM and 37% DSESM. These diets contained 28% protein and 5% lipid. Tilapia (3.90 ± 0.05 g) were randomly stocked into twelve 60‐L glass aquaria of a recirculation system at 18 fish per aquarium for 5 wk and then moved to the 600‐L flow‐through tanks for five more weeks. After 10 wk, there were no statistically significant differences (P > 0.05) in final mean weight, survival rate, and FCR among the four treatments. Results of the present study indicated that DSESM and EPSM could totally replace FM’s inclusion rate in commercial diets for juvenile tilapia. Furthermore, methionine did not appear to be limiting in practical diets using typical levels of CSM, DSESM, and MBM as primary protein sources.     

Substitution of Soybean Protein for Fish Protein in Formulated Diets for Red Swamp Crawfish Procambarus clarkii1

A 10 week laboratory growth trial was conducted with red swamp crawfish Procambarus clarkii to determine the amount of soybean protein that could be substituted for fish protein in formulated crawfish diets without reducing growth. Crawfish received 32% crude protein, isocaloric diets in which protein was supplied by soybean (soy) meal, menhaden fish meal or an isonitrogenous mixture of soybean and fish meal calculated to provide graded levels of each protein source. Dietary protein was provided as: 1) 100% soy protein; 2) 75% soy protein: 25% fish protein; 3) 50% soy protein: 50% fish protein; 4) 25% soy protein: 75% fish protein; and 5) 100% fish protein. Crawfish fed soy protein: fish protein (SP:FP) mixtures or fish protein alone exhibited better (P < 0.05) weight gain than crawfish fed a diet containing soy protein as the only protein source. Diets containing 25% soy protein: 75% fish protein (1:3 ratio) and 50% soy protein: 50% fish protein (1:1 ratio) produced greater (P < 0.05) weight gains than a diet in which fish protein was the sole protein source. Survival, feed efficiency ratio, maturation rate, net protein and energy retention, and body composition of crawfish did not differ (P > 0.05) among diets with SP:FP ratios of 1:3, 1:1 and 3:1. However, maximum (P < 0.05) weight gain occurred in crawfish fed the 1:3 SP:FP ratio. Although crawfish fed SP:FP ratios of 1:1 and 3:1 had lower weight gains in the laboratory than crawfish fed a 1:3 SP:FP ratio, SP:FP ratios of 1:1 and 3:1 might be adequate for supplemental diets fed to pond-reared crawfish that have access to natural sources of food.     

Replacement of Fishmeal with Soybean Meal in Male Tilapia (Oreochromis niloticusxO. aureus) Fingerling Diets at a Suboptimal Protein Level

A feeding trial was conducted to study the feasibility of using soybean meal (SBM) to replace fish meal (FM) as a protein source for tilapia feeds containing 24% dietary protein. Replacement levels were 0%, 33%, 67% and 100%. At each replacement level, methionine was either supplemented up to the amount that the 100% FM protein diet contained or not supplemented. The experiment was carried out for eight weeks in a recirculated water system. Fish fed diets in which 100% of the FM was replaced with SBM either with or without methionine supplementation had significantly ( P < 0.05) lower weight gain, feed conversion ratio, protein efficiency ratio and protein digestibility than that of the groups fed the diets containing FM as the sole source of protein. Also, fish fed diets in which 67% and 33% of the FM was replaced with SBM did not differ significantly ( P > 0.05) from that of the control group. These data suggest that when dietary protein level was suboptimal (24%), up to 67% of the FM protein in tilapin feeds can be replaced by hexane-extracted SBM protein without any adverse effect on tilapia growth and feed conversion ratio.     

Evaluation of Brewer's Waste as Partial Replacement of Fish Meal Protein in Nile Tilapia, Oreochromis niloticus, Diets

Abstract.— Brewer's waste is one of the promising protein source by-products for fish diets. A 10-wk feeding trial experiment involving five different diets with increasing levels of brewer's waste (32% crude protein) was carried out to evaluate the use of brewer's waste in tilapia diets in place of fish meal. Growth performance was compared against a control diet formulated to have similar composition to a typical commercial diet. Four experimental diets replaced successively 25, 50, 75, and 100% of the fish meal protein with brewer's waste. The diets were isonitrogenous and isocaloric. Results indicated that weight gain did not differ significantly ( P  > 0.05) with up to 50% replacement. Feed intake and utilization were depressed at high levels of brewer's waste. In addition, methionine of high replacement level diets was low. The results of the digestibility trial demonstrated that the brewer's waste used in this study has an apparent digestibility coefficient for protein of 70%. It was concluded that 50% of the fish meal protein in a typical commercial diet could be replaced with brewer's waste with no adverse effect on growth and feed utilization for tilapia.     

Comparison of the Nutritional Quality of Fish Meals Made from By-products of the Alaska Fishing Industry in Diets for Pacific Threadfin (Polydactylus sexfilis)

The nutritional quality of 13 commercial fish meals (10 from pollock, two from salmon, and one from cod) made from by-products of the Alaska fish processing industry was determined in diets for the marine fish Pacific threadfin Polydactylus sexfilis . Pelleted feeds were manufactured containing these meals as complete replacement of a low-temperature processed Norwegian fish meal (control). These feeds were fed to triplicate tanks of fish at the facilities of the Oceanic Institute, Hawaii for a period of 9 wk. At the end of the trial, the final weight, feed efficiency, protein efficiency ratio and survival data were subjected to ANOVA procedures. The performance parameters of the fish fed the white fish meals (pollock and cod) were not significantly different from the control. Of the two salmon meals, one promoted good growth and efficiency and one did not. It is concluded that the nutritional quality of Alaska white (pollock and cod) fish meals is equivalent to that of the low-temperature Norwegian fish meal and are of suitable quality for inclusion in commercial feeds for Pacific threadfin.     

Effect of Heated and Unheated Fish Silage as a Protein Source in Diets for Abalone Haliotis fulgens

Both unheated (US) and heated (HS) fish silage were evaluated as sole dietary protein sources in an artificial diet for the culture of juvenile abalone Haliotis fulgens . The fish silage was heated to reduce the level of hydrolysis and thereby increase the availability of nutrients. After 140 d of culture, growth rates of abalone fed the US- and HS-containing diets were 16.4 and 19.8 μm/d and were not significantly different despite greater leaching of protein and carbohydrate in the US-containing diet. Growth rates achieved with the US- and HS-containing diets were significantly lower than that achieved by feeding a commercially available diet used as a reference diet. Abalone that were fed the US- and HS-containing diets were then switched to a diet in which two-thirds of the total amount of silage was replaced with fishmeal. At the termination of the experiment, day 217, the abalone originally fed the US and HS diets had composite growth rates of 24.3 and 23.5 μm/d, while abalone that continued to be fed the commercial diet had a growth rate of 18.6 μm/d. Stability of the dry matter of the diets was not related to the level of protein leaching. Fish meal out performs fish silage as a dietary protein source for abalone. However, growth rates achieved still fall short of that needed to achieve a market size product within a 2-yr period of growth.     

Partial Replacement of Fish Meal with Plant Protein Sources Singly and in Combination in Diets for Summer Flounder,Paralichthys dentatus

Soybean meal (SBM), corn gluten meal (CGM), and canola protein concentrate (CPC) as alternative protein sources to fish meal (FM) were individually evaluated for growth performance at 0, 20, 30, 40, and 50% replacement with amino acid (AA) supplementation using juvenile summer flounder, Paralichthys dentatus, in an 8‐wk feeding. Two‐way ANOVA indicated no significant main effect for plant protein source, but a significant main effect for replacement level. Comparison of the individual treatments revealed significant differences in weight gain (WG) between the FM treatment and 50% replacement level for all protein sources, as well as between the FM treatment and 30% replacement with CPC. Replacement of FM with SBM at 40% resulted in the least cost/kg WG. In a follow‐up study, a combination of SBM–CGM–CPC at 40% replacement was evaluated with and without AA, phytase (0.2%), or taurine (1%), versus FM and SBM (40% replacement of FM) with AA. The SBM–CGM–CPC diet with either AA or taurine provided a significantly better food conversion ratio and less cost/kg WG than the SBM diet, and the SBM–CGM–CPC diet with taurine provided a significantly better protein efficiency ratio than the SBM diet. On the basis of these results, more study of taurine in plant protein diets for summer flounder appears warranted.     

The Influence of Different Rotifer and Artemia Enrichment Diets on Growth, Survival and Pigmentation in Turbot (Scophthalmus maximus L.) Larvae

An experiment was carried out on turbot larvae fed three different rotifer enrichment diets: Dry Selco, Protein Selco and ICES low-HUFA (an enrichment emulsion containing low amounts of highly unsaturated fatty acids—HUFA). Seven tanks were set up for each diet. After the rotifer stage, approximately seven days after hatching, the larvae were fed newly-hatched Artemia salina nauplii (AT-1; Brazil strain). From day 10, enriched Great Salt Lake Artemia nauplii were introduced. Each set of seven tanks was further subdivided and the larvae fed Arternia nauplii enriched with one of four enrichment diets: Dry Selco, Protein Selco, ICES low-HUFA or Super Selco. The rotifer enrichments had no significant effect on larval growth and survival. The nutritional value of the Artemia stage (day 13 to 26) was more important for the overall larval survival.     

The Effects of Substituting Selected Oilseed Protein Concentrates for Fish Meal in Rainbow Trout Oncorhynchus mykiss Diets

Three oilseed protein concentrates (soybean, canola, and sunflower) were evaluated to determine their potential, when supplemented with deficient essential amino acids, to partially or completely replace fish meal in diets fed to rainbow trout Oncorhynchus mykiss . Triplicate aquaria of juvenile trout (average weight of 12 g) were fed the experimental diets for 10 wk, at which time the average weight of the fish was approximately sixfold higher than the initial weight. Average fish weight gains on diets in which the protein component was 100% fish meal; 75% fish meal, 25% soybean protein concentrate; 50% fish meal, 50% soybean protein concentrate; and 75% fish meal, 25% sunflowerseed protein concentrate were not significantly different ( P < 0.05). The average weight of fish fed a commercial feed was significantly lower than that of fish fed the 100% fish meal diet, but not significantly different from fish fed the three other formulations mentioned above. Fish fed diets containing 50% fish meal, 50% canola protein concentrate; and 25% fish meal, 75% sunflowerseed protein concentrate had significantly lower average final weights than those of fish fed the other diets. Feed conversion ratio patterns among the dietary treatment groups reflected those of weight gain. Fish survival exceeded 95% on all diets. Apparent protein digestibility coefficients ranged from 79.5% (75% soybean protein concentrate, 25% canola protein concentrate) to 90.6% (100% soybean protein concentrate). The results of this study demonstrated that certain oilseed protein concentrates have good potential as protein sources in rainbow trout feeds when properly supplemented with essential amino acids.     

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

Three 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.     

Replacement of Fishmeal with a Blend of Poultry Byproduct Meal and Soybean Meal in Diets for Largemouth Bass,Micropterus salmoides

A feeding trial was conducted to evaluate the potential of replacing fishmeal with poultry byproduct meal (PBM) and soybean meal in diets for largemouth bass, Micropterus salmoides. A reference diet (C) contained 400 g/kg fishmeal, and 40 or 60% of the fishmeal was replaced with a blend of pet‐food‐grade PBM and soybean meal (diets PP1 and PP2) or a blend of feed‐grade PBM and soybean meal (diets PF1 and PF2). No significant differences were found in weight gain, nitrogen retention efficiency (NRE), condition factor, and body composition among fish fed diets PP1, PP2, PF1, and PF2. Feed intake and feed conversion ratio (FCR) were higher in fish fed diet PF1 than in fish fed diet PP1. No significant differences were found in weight gain, NRE, condition factor, and body composition between fish fed diet C and diets PP1, PP2, PF1, and PF2. The feed intake and FCR were lower in fish fed diet C than in fish fed diets PP2, PF1, and PF2. This study reveals that dietary fishmeal level for largemouth bass could be reduced to 160 g/kg by inclusion of PBM and soybean meal in combination.     

Replacing Fish Meal with Rendered Animal Protein Ingredients in Diets for Malabar Grouper,Epinephelus malabaricus,Reared in Net Pens

The potential of using rendered animal protein ingredients, poultry by‐products meal (PBM), meat and bone meal (MBM), and feather meal (FM), to replace fish meal in diets for malabar grouper, Epinephelus malabaricus, was evaluated in a 10‐week net pen experiment. Triplicate groups of fish (initial body weight 50.2 g) were fed eight isonitrogenous and isocaloric diets formulated to contain 52% crude protein and 9% crude lipid. The control diet contained 50% herring meal, whereas in the remaining seven diets, PBM was incorporated at 11.9 (PM1), 23.8 (PM2), and 35.7% (PM3) to replace 25, 50, and 75% of the fish meal; MBM was incorporated at 14.5 (MM1) and 29.0% (MM2) to replace 25 and 50% of the fish meal; and FM was incorporated at 9.4 (FM1) and 18.8% (FM2) to replace 25 and 50% of the fish meal. A raw fish (RF) diet was used as comparison to assess growth performance of fish fed the formulated diets. Feed intake was lower in fish fed the diets PM3 and FM2 than fish fed the control diet. There were no significant differences in weight gain (WG), final body weight (FBW), nitrogen retention efficiency (NRE), energy retention efficiency (ERE), and total nitrogen waste output (TNW) between fish fed the control diet and the diets PM1, PM2, PM3, MM1, MM2, and FM1. Fish fed the diet FM2 had lower WG, FBW, NRE, and ERE but higher TNW than that of fish fed the control diet. Feed conversion ratio (FCR) was higher in fish fed the diets MM2, FM1, and FM2 than fish fed the control diet. At the end of the experiment, there were no significant differences in whole‐body content of moisture, crude protein, and crude lipid among fish fed the formulated diets. WG, FBW, and TNW of fish fed the diet RF were higher, while FCR and NRE were lower than that of fish fed the control diet. No significant differences were found in feed intake, ERE, and whole‐body composition between fish fed the diet RF and the control diet. Results of the present study suggest that dietary fish meal level for malabar grouper can be lowered from 50 to 38% by incorporating PBM, MBM, or FM.     

Evaluation of Omega-3 Fatty Acid Enrichment of Artemia Nauplii as Food for Striped Bass Morone saxatilis Walbaum Larvae

Three enrichment techniques were evaluated for their efficiency in improving the dietary value of Artemia nauplii to striped bass larvae. Newly hatched Artemia nauplii from the Great Salt Lake (GSL) were enriched for 24 h using the following diets: 1) gelatin-acacia microcapsules containing menhaden oil rich in omega-3 polyunsaturated fatty acids (PUFA), primarily 20:5ω3 eicosapen-taenoic acid; 2) an emulsion of Baker's yeast and menhaden oil; and 3) marine Chlorella sp. Unfed San Francisco Bay (SFB) and GSL nauplii were used as controls. Enriched GSL (all three diets) and unfed SFB nauplii had significantly higher ( P < 0.05) levels of 20:503 than the unfed nauplii from GSL. Seven days post-hatched (day 0) striped bass larvae were reared for 21 d on enriched or unfed nauplii. On day 21, wet weight and total length of striped bass larvae fed enriched GSL nauplii and unfed SFB nauplii were significantly greater ( P < 0.05) than those fed unenriched GSL nauplii. The enrichment of the GSL nauplii appeared to increase the eicosapentaenoic acid content and enhance the growth of the striped bass larvae.     

饵料对扁玉螺浮游幼虫存活与生长的影响

采用投喂小球藻、角毛藻、鱼腥藻、螺旋藻以及小球藻和角毛藻5组饵料分别投喂扁玉螺浮游幼虫,每天测定壳宽和存活率,结果表明,8天后,投有角毛藻的2组存活率较高,生长较快。笔者认为,角毛藻是扁玉螺浮游幼虫的适合饵料。     

Evaluation of Soybean Proteins as Replacements for Menhaden Fish Meal in Practical Diets for the Red Drum Sciaenops ocellatus

A series of growth trials was conducted to evaluate the use of soy protein as a replacement for fish protein in isonitrogenous practical diets for juvenile red drum Sciacnops ocellatus. Feeds were offered at or in excess of satiation to juvenile red drum maintained at 26–28 C and a salinity of 25–35 ppt. In the first growth trial, red drum were offered one of four diets containing graded levels of menhaden fish meal, replacing solvent-extracted soybean meal and soy-protein isolates. Differences in weight gain, survival and feed efficiency ratios of the fish corresponded to increases in fish meal content of the diets. Due to poor performance of the fish maintained on the low (15%) fish meal diet, a methionine supplement was introduced into this diet at the midpoint of the growth trial. A positive increase in growth indicated a dietary deficiency of methionine and/or total sulfur amino acids in the unsupplemented diet. A positive response to dietary fish meal also occurred in the second growth trial despite the supplementation of L-methionine in the test diets. In low fish meal diets the utilization of solvent extracted soybean meal or a soy-protein isolate resulted in similar growth responses. Hence, the presence of an antinutrient did not likely cause reduced growth rates. In the third feeding trial, weight gain also increased with increasing fish meal content of the diet despite the equalization of digestible protein and selected amino acids. There were no significant differences in whole-body compositions which indicated similar biological value of the diets (protein digestibility, amino acid balance and energy availability). The singular deletion of fish-solubles, glycine, lysine and methionine from the diet containing the lowest level of fish meal (10 g/100 g diet) did not result in significant changes in weight gain. This indicated that these components did not add to the nutritive value and/or palatability of this formulation. The final experiment was designed to evaluate the response of red drum to a control diet (high fish meal) as compared to a low fish meal diet with and without potential attractants/palatability enhancers. Weight gain and feed efficiency ratios of fish offered the low fish meal diet supplemented with seafood flavor or fish flavor #2 were not significantly different from the control (high fish meal diet). Based on the results of this study, with suitable formulation restrictions, soy protein is acceptable for inclusion in practical diet formulations for red drum. However, soy protein itself does not appear replete in sulfur-containing amino acids and does not have acceptable palatability properties. Consequently, feeds containing reduced levels of marine proteins could require suitable attractants and/or amino acid supplements.     

Comparison of Satiate and Restricted Feeding of Channel Catfish with Diets of Varying Protein Quality in Production Ponds

A 2 × 3 factorial experiment was conducted using satiate and restricted feeding with 32% crude protein diets containing low, medium, and high quality protein. Protein quality in the experimental diets was varied primarily by substituting peanut meal and cottonseed meal for soybean meal. Percentages of lysine, the first-limiting amino acid, were 1.14, 1.33, and 1.61 in the low, medium, and high quality protein diets respectively. Digestible energy concentration of the diets was 2.9 kcal/g. Channel catfish were grown from an average weight of 47 g to marketable size over a 15 wk period at a stocking density of 13,750 fish/ha in 400 m² earthen ponds. Each treatment was replicated in three ponds. Fish in the satiation group were fed as much as they would consume each day for the 15 wk experimental period. Fish in the restricted group were fed as much as they would consume until the daily feed allowance reached 65 kg/ha, which was reached at approximately week 5 of the experiment, and thereafter, there was no further increase in feed allowance. There was no significant interaction between feeding regimen and dietary protein quality for weight gain or feed conversion. Weight gain and feed efficiency under both satiation and restricted feeding increased linearly as protein quality increased. Protein quality had no influence on protein efficiency ratio (PER) under satiate feeding but had a positive effect on PER under restricted feeding. Protein quality had a positive linear effect on dressing percentage under restricted feeding, but in those fish fed to satiation, dressing percentage only increased between the low and high quality protein treatments. Protein quality had a negative linear effect on muscle fat but had no effect on visceral fat under satiate or restricted feeding. These results indicate that channel catfish are sensitive to protein quality differences in practical feeds at both satiate and restricted feeding rates, and that reduction in protein quality reduces dressing yield and increases muscle fat in food size fish.