Iron Methionine and Iron Sulfate as Sources of Dietary Iron for Channel Catfish Ictalurus punctatus

The dietary iron requirement for normal growth and optimum hematological values and bioavailability was determined for channel catfish Ictalurus punctatus fingerlings using egg-white based diets supplemented with 0,5,10,20,60, and 180-mg iron/kg from iron methionine or 20, 60, and 180-mg iron/kg from iron sulfate. The basal diet which contained 9.2-mg iron/kg, 34% crude protein and 3.1 kcal of digestible energy/g was fed to channel catfish fingerlings (8.5 g) in triplicate flow-through aquariums to satiation twice daily for 8 wk. Fish fed the basal diet without iron supplementation exhibited poor growth throughout the 8-wk period. Fish fed iron-supplemented diets did not differ with regard to final weight gain. Survival, feed conversion, total blood cell count, mean corpuscular hemoglobin concentration, serum iron, total iron binding capacity, and transferrin saturation were not significantly affected by dietary iron level. Hemoglobin, hematocrit, mean corpuscular hemoglobin, and mean corpuscular volume were significantly lower in fish fed the basal diet. These values were also consistently lower for fish fed diets with 5 and 10-mg iron/kg from iron methionine. However, differences were not always significant. Results of this study indicate that supplementation of 5-mg iron from iron methionine was sufficient for growth. However, a supplemental iron level of 20-mg/kg diet or a total iron level of 30-mg/kg of diet appeared to be needed for optimum hematological values. Iron methionine and iron sulfate were equally effective in preventing anemia in channel catfish.     

Use of Corn Germ Meal in Diets for Pond‐Raised Channel Catfish,Ictalurus punctatus

Corn germ meal (CGM) is a by‐product of corn milling. On the basis of its nutrient composition and digestibility values, it appears to be a suitable ingredient for use in channel catfish, Ictalurus punctatus, diets. A study was conducted to examine the use of various levels of CGM in diets for pond‐raised channel catfish. Four 28% protein diets containing 0, 15, 25, and 35% CGM were evaluated. Fingerling channel catfish (mean initial weight: 71 g/fish) were stocked into 24, 0.04‐ha ponds at a rate of 14,826 fish/ha. Fish were fed once daily to apparent satiation for a 167‐d growing season. No significant differences were observed in total amount of diet fed, diet consumption per fish, net yield, weight gain, feed conversion ratio, survival, fillet yield, and fillet protein, fat, and moisture concentrations among fish fed diets containing various levels of CGM. Carcass yield decreased linearly as dietary CGM levels increased. Depending on prices, CGM can be used interchangeably with corn gluten feed in channel catfish diets as replacements for corn, wheat middlings, and soybean meal to reduce feed cost.     

Effect of Dietary Total Protein and Animal Protein on Growth and Feed Efficiency of Juvenile Channel Catfish Ictalurus punctatus and Their Response to Edwardsiella ictaluri Challenge

A laboratory study was conducted to evaluate effects of dietary total protein and animal protein source and concentration on growth and feed efficiency of juvenile channel catfish Ictalurus punctutus and their response to Edwardsiellu ictuluri challenge. Eight diets evaluated were: three diets containing either 28, 32, or 36% crude protein with 6% menhaden fish meal and 6% meat and bonehlood meal and five diets containing 32% crude protein with either no animal protein, 68 or 12% menhaden fish meal, or 6% or 12% meat and bonehlood meal, respectively. Twenty channel catfish with an average weight of 6.6 g/fish were stocked into each of forty 110-L flow-through aquaria (five aquaridtreatment). Fish were fed to approximate satiation twice daily for 9 wk. Fish in each tank were then exposed to E. ictaluri . There were no differences in feed consumption, weight gain, feed efficiency, and survival before and after challenge among fish fed diets containing 28, 32, or 36% protein with 6% menhaden fish meal and 6% meat and bone/ blood meal. Fish fed a 32% all-plant protein diet had weight gain and feed efficiency similar to fish fed diets containing 12% menhaden fish meal, but had a higher weight gain than fish fed a 32% protein diet containing 6% meat and bonehlood meal. No significant differences were observed in survival after E. ictuluri challenge among fish fed diets containing the various levels of animal proteins. Results indicate that dietary protein levels varying from 28% to 36% do not appear to affect growth, feed efficiency. and E. icraluri resistance or susceptibility in fingerling channel cattish fed to satiation and raised from approximately 7 to 56 g under laboratory conditions. Data also demonstrate that a 32% all-plant protein diet can be fed to small fingerling channel catfish without adversely affecting growth, feed efficiency, or resistance to E. ictuluri .     

Replacement of Soybean Meal in Channel Catfish, Ictalurus punctatus, Diets with Cottonseed Meal and Distiller's Dried Grains with Solubles

Two pond experiments were conducted to evaluate cottonseed meal (CSM), distiller's dried grains with solubles (DDGS), and supplemental lysine as replacements for soybean meal (SBM) in channel catfish diets. In Experiment 1, fish fed diets in which SBM was totally replaced with CSM gained similar weight as fish fed control diet, but fish fed CSM diet in Experiment 2 had 9.5% lower weight gain than fish fed control diet. In both experiments, feed conversion increased significantly for fish fed CSM diet. There were no consistent trends in body composition of fish fed CSM diet versus control diet. Fish fed the DDGS + SMB diet had higher (Experiment 1) or similar (Experiment 2) weight gain than fish fed control diet. Feed conversion ratio was significantly lower in both experiments for fish fed SBM + DDGS diet than that of fish fed control diet. Body fat tended to be higher in fish fed SBM + DDGS diet compared to fish fed control diet. It appears that about 50% of SBM can be replaced with CSM + lysine in catfish diets without negatively affecting fish performance. Further, DDGS can be used up to at least 30% when the diet is supplemented with lysine.     

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.     

Effects of Long-Term Feeding of Cottonseed Meal on Growth,Testis Development,and Sperm Motility of Male Channel Catfish Ictalurus punctatus Broodfish1

The effects of long-term feeding of cottonseed meal on growth, testis development, and sperm motility of male channel catfish Ictulurus punctatus were studied. Brood-sized male channel catfish were stocked into 0.04-ha earthen ponds in April 1992 at the rate of 120 fish per pond. The fish were fed a diet (32% protein floating catfish feed) containing either 0, 25, 375, or 52% cottonseed meal to satiation daily, except for winter months when fish were fed on days when the water temperature was 15 C or above. Fish were harvested in July 1994. Feed consumption was similar for fish regardless of dietary treatment. Feed conversion was higher for fish fed the two highest levels of cottonseed meal and weight gain was depressed in these groups. Testis weight, gonosomatic index, and sperm motility were not negatively affected by high levels of dietary cottonseed meal indicating that reproductive capacity was not diminished. Thus it wonld appepr that up to 52% cottonseed meal could be used in the diets of brood-sized channel catfish unless maximum gain is important. In a practical situation, growth rates of brood-sized channel catfish are not as important as reproductive performance.     

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.     

Effects of fish oil and partial fish meal substitution with oilseed oils and meals on growth performance, nutrient utilization and health of the rainbow trout Oncorhynchus mykiss

A feeding trial was conducted to investigate the effects of the replacement of dietary fish meal and fish oil with oilseed meals (soybean or canola) and canola oil on growth, nutrient utilization, body composition, diet digestibility and hematological parameters of rainbow trout Oncorhynchus mykiss. Seven diets were used; the control diet (designated FM) contained fish meal and fish oil as the main protein and lipid sources. For the experimental diets, 40% of fish meal protein was substituted with soybean meal, canola meal or a soybean/canola meal mixture, and these diets (designated SM, CM and SCM, respectively) contained fish oil as the lipid source. Three additional diets (SM?+?CO, CM?+?CO and SCM?+?CO) were formulated with the same vegetable protein meals but with fish oil replaced by canola oil. Fish were fed twice daily to apparent satiation for 11?weeks. The growth of fish fed the CM?+?CO diet was significantly lower than that of fish fed the FM, SCM, SM?+?CO and SCM?+?CO diets. The feed conversion ratio (FCR) was significantly better in fish fed the FM and SCM?+?CO diets than in fish fed the CM and CM?+?CO diets. Furthermore, feed intake was significantly lower for fish fed the CM?+?CO diet than in fish fed the SCM diet, and lipid digestibility of the CM?+?CO diet was significantly lower than that of all other diets. No significant differences of body composition were observed. Circulating leukocyte levels, leukocyte ratios and serum lysozyme activity remained unaffected by dietary treatment. However, it was observed that fish fed the CM?+?CO diet displayed hematocrit levels significantly lower (P?<?0.05) than that of fish fed the other diets. The results indicate that when diets contain either fish oil or canola oil, canola meal and soybean meal can be incorporated into rainbow trout feeds at a combined 32% inclusion level (replacing 40% of fish meal protein) without inducing significant negative effects on growth, nutrient utilization or health.     

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.     

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.     

Effects of Feeding Diets with and without Fish Meal on Production of Channel Catfish,Ictalurus punctatus,Stocked at Varying Densities

ABSTRACT

Animal protein, generally fish meal, has traditionally been used in the diet of channel catfish. However, our previous research indicates that animal protein is not needed for growing stocker-size catfish to food fish when the fish are stocked at densities typical of those used in commercial catfish culture. Whether this holds when fish are stocked at high densities is not known; thus, we conducted an experiment to evaluate the effect of feeding diets with and without fish meal to channel catfish stocked in earthen ponds at different densities. Two 32% protein-practical diets containing 0% or 6% menhaden fish meal were compared for pond-raised channel catfish, Ictalurus punctatus, stocked at densities of 14,820, 29,640, or 44,460 fish/ha. Fingerling channel catfish with average initial weight of 48 g/fish were stocked into 30 0.04-ha ponds. Five ponds were randomly allotted for each fish meal level?×?stocking density combination. Fish were fed once daily to satiation for two growing seasons. There was a significant interaction between stocking density and fish meal for net production; net production increased in fish fed a diet containing fish meal compared with those fed an all-plant diet at the highest stocking density, but not at the two lower stocking densities. Net production of fish fed diets with and without fish meal increased as stocking density increased. Viewing the main effect means, weight gain decreased and feed conversion ratio increased for fish stocked at the two highest densities, and survival was significantly lower at the highest stocking density. Visceral fat decreased in fish at the two highest stocking densities. Body composition data were largely unaffected by experimental treatment except for a reduction in percentage filet fat in fish at the highest stocking density, and fish that were fed diets containing fish meal had a lower percentage fillet protein and a higher percentage fillet fat. It appears that at stocking densities two to three times higher than generally used, animal protein (fish meal) may be beneficial in the diet of channel catfish. In regard to stocking densities, high stocking results in higher overall production, but the average fish size decreased as stocking density increased.     

Comparison of Various Animal Protein Sources for Growth, Feed Efficiency, and Body Composition of Juvenile Channel Catfish Ictalurus punctatus

A laboratory study was conducted to compare different animal protein sources in diets containing 32% protein for channel catfish Ictalurus punrtatus . The experimental diets were practical-type diets and formulated to meet or exceed all known nutrient requirements for channel catfish. Twenty juvenile channel catfish (initial weight: 6.4 g/fish) were stocked into each of 25 110-L flow-through aquaria (five aquaria/treatment). Fish were fed twice daily to approximate satiation for 9 wk. Fish in each aquarium were counted and weighed collectively every 3 wk. No significant differences were observed in feed consumption, weight gain, feed efficiency, survival, percentages visceral fat and fillet yield, or proximate composition of fillets among channel catfish fed diets containing either 5% menhaden fish meal, meat and bone/blood meal, catfish by-product meal, poultry by-product meal, or hydrolyzed feather meal with supplemental lysine. The data indicate that these animal protein sources can be used interchangeably in diets for channel catfish without affecting fish growth, feed efficiency, or body composition.     

Substitution of Soybean Meal with Cottonseed Meal in Pond Feeds for Channel Catfish Reared at Low Densities

Cottonseed meals were evaluted as partial and complete replacements for soybean meal in pond feeds for channel catfish grown at densities of 5,300/ha. The following dietary treatments were used: 1) glanded cottonseed meal (GC) in which ½ of the soybean meal was replaced; 2) glandless cottonseed meal (GLC) in which all of the soybean was replaced, 3) a control feed (C) typical of commercial catfish feeds. The feeding trial was conducted in 0.04 ha earthen ponds for a period of 176 days. Natural prey species were present in all ponds. Final weights and condition factors of fish fed the GC feed were reduced compared to those fed the GLC or C feeds. This response did not appear to be related to dietary gossypol levels. Even though the GLC feed appeared to be deficient in available lysine, final weight and feed conversion of fish fed the GLC feed were equal to those fed the C feed. Possible nutrient contributions of natural food available in the ponds could not be determined. There were no significant differences in feed conversions or dressout percentages of fish regardless of dietary treatment. Fish fed the GLC feed exhibited a higher percentage of fat and lower percentages of moisture, protein and ash (dry weight basis) in edible tissue than fish fed the other feeds. Free gossypol levels in edible fish tissue were below 100 ppm.     

Replacement of Dietary Fish Meal with Poultry By‐product Meal and Soybean Meal for Golden Pompano,Trachinotus ovatus,Reared in Net Pens

Two 8‐wk feeding trials were conducted to examine the effect of replacing dietary fish meal with poultry by‐product meal (PBM) and soybean meal (SBM) on growth, feed utilization, body composition, and wastes output of juvenile golden pompano, Trachinotus ovatus (initial body weight 16.7 g), reared in net pens. A control diet (C) was formulated to contain 35% fish meal. In Trial I, dietary fish meal level was reduced to 21, 14, 7, and 0% by replacing 40, 60, 80, and 100% of the fish meal in diet C with PBM. The weight gain (WG), nitrogen retention efficiency (NRE), and energy retention efficiency (ERE) decreased, while the feed conversion ratio (FCR) and total waste output of nitrogen (TNW) increased, with the fish meal level reducing from 35 to 21%. No significant differences were found in the hepatosomatic index, viscersomatic index, and body composition between fish fed diet C and test diets. In Trial II, a 2 × 2 layout was established, and 40 and 60% of the fish meal in diet C was replaced by either PBM or SBM. At the same fish meal replacement level, the WG and NRE were higher and the FCR and TNW were lower in fish fed the diets with fish meal replaced by PBM than in fish fed the diets with fish meal replaced by SBM. The results of this study indicate that more than 21% fish meal must be retained in diets for golden pompano when PBM or SBM is used alone as a fish meal substitute.     

Evaluation of Low‐protein Alternative Diets for Pond‐raised Hybrid Catfish,Ictalurus punctatus × Ictalurus furcatus

A study was conducted to evaluate low‐protein traditional or alternative diets for pond‐raised hybrid catfish, Ictalurus punctatus × Ictalurus furcatus. Three 24% protein diets containing decreasing levels of soybean meal (30, 20, and 15%) and increasing levels of cottonseed meal and corn germ meal were compared with a 28% protein control diet. Hybrid catfish fingerlings (mean initial weight = 71 g/fish) were stocked into 20 earthen ponds (0.04 ha) at a density of 14,826 fish/ha with five ponds per dietary treatment. Fish were fed once daily to apparent satiation for a 191‐d growing season. There were no significant differences in total diet fed, net yield, weight gain, feed conversion ratio (FCR), survival, or fillet proximate nutrient composition among dietary treatments (P ≥ 0.10). However, regression analysis showed for fish fed 24% protein diets there was a linear increase in FCR as soybean meal levels decreased (P = 0.06). Compared with fish fed the 28% protein control diet, fish fed 24% protein diets had lower carcass and fillet yield. Results demonstrate a 24% protein alternative diet containing 20% soybean meal may be substituted for 28% protein diets for hybrid catfish during food fish production.     

Effects of Replacement of Fish Meal by Soybean Meal and Supplementation of Methionine in Fish Meal/Soybean Meal-based Diets on Growth Performance of the Southern Catfish Silurus meridionalis

Two experiments (Experiment I and 11) were conducted to evaluate the effects of dietary soybean meal (SBM) with or without supplementation of methionine on the growth performance of the southern catfish Silurus meridionalis. Fish were fed isonitrogenous (48% crude protein) and isoenergetic (20 KJ/g gross energy) diets for 8 wk in a recirculating rearing system. In Experiment I, six diets containing 0.0,11.6, 23.1, 34.7, 46.3, and 57.9% solvent‐extracted SBM as replacement of 0% (control), 13%, 26%, 39%, 52% and 65% fish meal (FM) protein were formulated to examine the effects of dietary SBM on growth performance. Each of the six diets was randomly fed to triplicate tanks, and each tank was stocked with 10 fish (average initial weight 23.78 ± 0.09 g). Fish fed the diets with 13%, 26%, and 39% protein from SBM had significantly higher or similar specific growth rate (SGR) compared with the control group. However, SGR in fish fed the diets with 52% and 65% protein from SBM was significantly lower than other groups (P < 0.05). These results showed that 39% of FM protein could be replaced by SBM protein in diets of the southern catfish without significantly reducing growth. In Experiment II, seven diets were formulated to examine the effects of supplemental methionine on the growth performance of this fish (initial weight of 19.73 ± 0.36 g) fed diets at the two SBM substitution level (SL) for replacing 39% or 52% FM protein. The control diet was the same as that (0% SL) in Experiment I. Three methionine levels (0.00%, 0.12%, or 0.26% at 39% SL, 0.00%, 0.21%, or 0.33% at 52% SL) were separately supplemented to represent two endogenous controls (no methionine supplementation), and to produce diets with the same methionine content as that found in either the body carcass of this fish or the control diet (0% SBM protein), respectively. The results showed that there were no significant differences in feeding rate, digestibility and SGR between fish fed the diets with and without supplementation of methionine at 39% SL. However, supplementation of methionine at 52% SL results in significantly higher SGR and feed efficiency (FE) than that of fish fed the diet without supplementation (P < 0.05). It is suggested that the endogenous methionine content in the diet at 39% SL could meet the requirement for the growth, but is insufficient at 52% SL. The results of the present study indicate that methionine is one of the limiting factors in SBM‐based diets to growth of the southern catfish, and supplementation of methionine into diets containing a high content of SBM could improve the growth performance of this fish.     

Microbial Phytase Can Replace Inorganic Phosphorus Supplements in Channel Catfish Ictalurus punctatus Diets1

Abstract.– Juvenile channel catfish Ictalurus punctatus (initial weight: 6.8 g/fish) were fed four practical diets containing 0, 250, 500, and 750 units of microbial phytase/kg and a diet containing 1% feed grade dicalcium phosphate (but no microbial phytase) under laboratory conditions for 12 wk. Fish fed the diets containing 250 units of microbial phytase/kg and above consumed more feed, gained more weight, and had a lower feed conversion ratio (FCR) in comparison to fish fed the basal diet containing no microbial phytase. Fish fed the diet containing dicalcium phosphate had intermediate weight gain and feed conversion ratio as compared to fish fed the basal diet and diets containing microbial phytase. Bone ash and phosphorus concentrations were lower for fish fed the basal diet than for fish fed other diets. No differences in weight gain, feed consumption, FCR, bone ash and bone phosphorus were observed among fish fed the diets containing various levels of microbial phytase. Fish fed the diet containing dicalcium phosphate had a lower bone phosphorus concentration than fish fed diets containing microbial phytase. Fecal phosphorus concentrations were lower for fish fed the diets containing microbial phytase than for fish fed the basal diet and the diet containing dicalcium phosphate. Results from the present study indicated that addition of 250 units of microbial phytase/kg to practical diets can effectively improve bioavailability of phytate phosphorus to channel catfish and may possibly eliminate the use of an inorganic phosphorus supplement in channel catfish diets. However, these data must be verified in trials conducted in ponds, prior to recommending removal of supplemental phosphorus from channel catfish diets.     

Effects of varying dietary compositions using common feed ingredients on growth and feed efficiency of pond‐raised channel catfish Ictalurus punctatus (Rafinesque)

Two experiments were conducted to evaluate various ingredient combinations in a 28% or 32% protein diet for optimum performance of channel catfish Ictalurus punctatus. All diets contained soybean meal and corn, but with or without cottonseed meal, wheat middlings or fish meal (FM). Channel catfish fingerlings were stocked into 0.04 ha earthen ponds at 18 530 fish ha^?1. Fish were fed one of eight diets once daily to apparent satiation for two growing seasons. Results demonstrated that the dietary ingredient composition used had significant effects on fish performance, but magnitude of differences was relatively small. Overall, diets containing FM resulted in greater weight gain (Experiments 1 and 2) and lower feed conversion ratio (Experiment 1) than fish fed all‐plant diets. However, certain combinations of plant ingredients provided the similar fish growth as some diets containing FM. There were no significant differences in weight gain between fish fed soybean meal–corn or soybean meal–corn–wheat middlings‐based diets with cottonseed meal or FM. The use of wheat middlings in the diet had no significant effects on fish production characteristics.     

Evaluation of Corn Gluten Feed and Cottonseed Meal as Partial Replacements for Soybean Meal and Corn in Diets for Pond‐raised Hybrid Catfish,Ictalurus punctatus×I. furcatus

This study examined the use of corn gluten feed (CGF) and cottonseed meal (CSM) to partially replace soybean meal and corn in diets for pond‐raised hybrid catfish, Ictalurus punctatus×I. furcatus. Five 28% protein diets containing various combinations of CGF and CSM were evaluated. Fingerling hybrid catfish (mean initial weight: 45 g/fish) were stocked into 25, 0.04‐ha ponds at a rate of 14,826 fish/ha. Fish were fed once daily to apparent satiation for a 179‐d growing season. CGF at 30% of the diet (10% CSM) and a combination of CGF and CSM up to 25% each did not affect physical quality (percentages floatability and feed dust) of the diet. No significant differences were observed in total amount of diet fed, net yield, diet consumption, weight gain, feed conversion ratio (FCR), survival, and fillet proximate nutrient composition among fish fed various diets. Results show that hybrid catfish can utilize CGF at levels up to 30% of the diet (10% CSM), and a combination of CGF and CSM up to 25% each without significantly affecting growth, diet consumption, FCR, and fillet proximate nutrient composition. However, a combination of CGF and CSM at 20% each and above reduced carcass yield.     

Evaluation of Plant and Animal Source Proteins for Replacement of Fish Meal in Practical Diets for the Largemouth Bass Micropterus salmoides

Two feeding trials were conducted with juvenile largemouth bass Micropterus salmoides to evaluate alternative plant and animal source proteins for their ability to replace fish meal in practical diets. The first trial was designed to identify the most promising candidates. The second trial was conducted to evaluate how much of the fish meal could be replaced by those candidates. In Study 1, feed‐trained largemouth bass (3.1 ± 0.7 g) were randomly stocked into 18114‐L glass aquaria at 25 fish per aquarium. Fish were fed one of six experimental diets, each containing approximately 38% crude protein and 10% crude lipid, to apparent satiation twice daily. The control diet (CTL) contained 30% fish meal and 34.5% soybean meal. Diets 2–6 each contained 15% fish meal and at least 34.5% soybean meal with the remainder of the protein made up of either meat and bone meal (MBM), soybean meal (SBM), poultry by‐product meal (PBM), a 50150 mixture of blood meal and corn gluten meal (BM/CG), or 50150 mixture of hydrolyzed feather meal and soybean meal (FMISBM). There were three replicate aquaria per dietary treatment. After 12 wk, there was no significant difference (P > 0.05) among treatments in survival which averaged 92% overall. Only fish fed the PBM or BM/CG diets had average individual weights and feed conversion efficiencies that were not significantly different (P > 0.05) from the control diet (CTL). In Study 2, the formulation of the control diet (CTL) remained the same. Based on their performance in the first trial, PBM and BM/CG were chosen to now replace 75 or 100% of the fish meal. Fish were stocked at an average weight of 6.9 ± 1.7 g. After 11 wk, fish fed diets containing the BM/CG mixture at both levels were significantly smaller (P 5 0.05) than fish fed other diets and at 100% replacement survival was reduced. Fish fed diets containing poultry meal as the primary protein source performed as well as those fed the control diet (CTL). It appears that PBM can completely replace fish meal in diets for juvenile largemouth bass without adverse effects on growth, feed efficiency, or body composition.