Richard T. Lovell

Organic selenium sources, selenomethionine and selenoyeast, have higher bioavailability than an inorganic selenium source, sodium selenite, in diets for channel catfish (Ictalurus punctatus)

Abstract Channel catfish ( Ictalurus punctatus ) fingerlings (average initial weight, 1.70g) were fed casein-based purified diets supplemented with 0, 0.02, 0.06, 0.20 or 0.40 mg of selenium per kg from sodium selenite (Na 2 SeO 3 ), selenomethionine (Se-M) or selenoyeast (Se-Y) for 9 weeks. Data for weight gain and glutathione peroxidase activity were subjected to regression analysis to determine dietary requirements and relative bioavailability for the various selenium sources. Broken-line analysis showed that minimum supplemental dietary selenium requirements as Na 2 SeO 3 , Se-M and Se-Y for weight gain were 0.28, 0.09 and 0.11 mg kg −1 , and for liver glutathione peroxidase activity were 0.17, 0.12 and 0.12 mg kg −1 diet. Relative bioavailability values of Se-M and Se-Y compared to Na 2 SeO 3 were 336 and 269% for growth, and 147 and 149% for glutathione peroxidase activity, respectively. Selenium from Se-M and Se-Y showed significantly higher rates of accumulation in liver and muscle than selenium from Na 2 SeO 3 . This study indicates that selenium allowance in diets of channel catfish can be reduced when selenomethionine or selenoyeast replaces inorganic selenium.

Free lysine (l-lysine · HCl) is utilized for growth less efficiently than protein-bound lysine (soybean meal) in practical diets by young channel catfish (Ictalurus punctatus)

Abstract Two 10-week feeding experiments were conducted with channel catfish fingerlings in aquaria to compare the efficiency of utilization for growth of free versus protein bound lysine in practical diets. In experiment 1, a basal, 26% protein diet, deficient only in lysine, was formulated with a combination of peanut meal and corn gluten meal as the primary protein source. The diet was then supplemented with graded levels of lysine by either adding l —lysine · HCl or substituting soybean meal for the peanut meal—corn gluten meal combination to produce two series of diets with increasing concentrations of either free lysine or protein-bound lysine. In experiment 2, the basal diet contained sesame meal as the primary protein source and was supplemented with free or protein-bound lysine as in experiment 1. Slope ratio analysis of response data showed that the efficiency of utilization of protein-bound lysine in soybean meal relative to free lysine from lysine-HCl was 196 and 163% for experiments 1 and 2, respectively, based on weight gain. A subsequent feeding experiment was conducted in which the peanut meal-corn gluten meal basal diet was supplemented with lysine alone or with lysine plus histidine, isoleucine, threonine, and tryptophan to match the essential amino acid composition of the diet in which soybean meal provided the protein. Supplementation of the basal diet with the additional amino acids did not improve fish weight gain relative to that from supplementation with lysine alone. Overfortification of the basal diet with free lysine improved weight gain of fish to equal that obtained with the diet containing soybean meal. Loss of lysine due to leaching of diets in water was 12.7 and 2.0% of the original lysine concentration for free lysine and protein-bound lysine, respectively. When leaching losses are subtracted from the lysine concentrations in the test diets, the efficiency of utilization of protein-bound lysine is still higher than that of free lysine, 175 and 146%, based on weight gain, for experiments 1 and 2, respectively. These results indicate that protein-bound lysine is more efficiently utilized than free lysine in practical type diets for young channel catfish.

Partial substitution of soybean meal with animal protein sources in diets for channel catfish.

Nine-week laboratory feeding experiments were conducted to evaluate partial substitution of animal protein sources into a 32% protein soybean-meal-corn basal diet for channel catfish (Ictalurus punctatus) fingerlings. In the first experiment, substitution of 5, 10, 20, and 40% menhaden fish meal into the basal diet resulted in increases in weight, protein, and fat gains as fish mean was increased to 20% (P < 0.05), and an increase in fat gain as fish meal was increased to 40% (P < 0.05). In the second experiment, the basal diet was supplemented with 5 and 10% fish meal or isonitrogenous amounts of protein from meat and bone meal (5.6 and 11.3%), blood meal (3.4 and 6.8%), and a 60:40 combination of meat and bone and blood meals (5 and 10%). Weight, protein, and fat gains were improved (P < 0.10) when the lower level of each animal protein, except blood meal, was substituted into the basal diet. Increasing the dietary level of each animal protein, except blood meal, improved gains over those from diets containing the lower level of the animal protein (P < 0.10). Fish meal improved gains more than isonitrogenous levels of the other animal proteins at both dietary levels (P < 0.10). Estimated amino-acid contents of the diets indicate that the increase in growth produced by including fish meal may be explained on the basis of increasing dietary levels of the most limiting amino acids; however, the increase in growth effected by including the other animal protein sources in the diet cannot be explained on that basis. Food consumption during the first 3 days of experiment indicated that inclusion of fish meal, meat and bone meal, or the meat and bone-meal-blood-meal combination improved diet palatability.

Effect of restricted feeding regimens on compensatory weight gain and body tissue changes in channel catfish Ictalurus punctatus in ponds

Year 2 channel catfish averaging 41 g were stocked in 0.04 ha earthen ponds at the rate of 13 750 fish ha−1. When daytime water temperature reached 25 °C, one group of fish (four ponds per group) was placed on restricted feeding for 3 weeks during which time the fish were fed once every 3 days, another group was on restricted feeding for 6 weeks, another group was on restricted feeding for 9 weeks, and another group (control) was on full feeding continuously for the 18 week feeding period. All fish were fed as much as they would consume when placed on full feeding. After 18 weeks, the fish on restricted feeding for 3 weeks weighed approximately the same as the control, in fact, they required only 3 weeks on full feeding to catch up with the control. Fish on restricted feeding for 6 and 9 weeks weighed less (P < 0.05) than the control at the end of the experiment; however, their gains were 90% and 86%, respectively, as much as the control. Feed conversion for the 18 week period was the same for all treatments. Dressing yield and body composition (total fat, protein, moisture) were the same for all treatments at the end of the trial. Immediately following the period of feed deprivation, body fat in all restricted fed fish was lower than in the control fish but within 3 weeks on full-feeding body fat in these fish increased to levels equal to those of the control fish. Muscle fiber diameter was not different among treatments at any period. These results indicate that Year 2 channel catfish in production ponds can partially or completely recover in weight gain and body composition from periods of limited feeding provided they are subsequently fed to satiety.

Dietary lipid sources influence responses of channel catfish (Ictalurus punctatus) to challenge with the pathogen Edwardsiella ictaluri

Two experiments were conducted to evaluate the effect of feeding various lipid sources at high and low water temperatures on responses of channel catfish to challenge (25°C) with Edwardsiella ictaluri. Semipurified diets were fed which contained 7% beef tallow, corn oil, linseed oil, menhaden oil or a 1:1:1 mixture of beef tallow, corn oil and menhaden oil. In Experiment 1, fish (14.3±0.3 g average initial weight) fed the menhaden oil and linseed oil diets for 13 weeks at 28°C had lower survival than fish fed the other diets (P<0.05). In Experiment 2, the fish (0.7±0.01 g average initial weight) fed the menhaden oil and the linseed oil diets for 9 weeks at 28°C also had lower survival than fish fed the other diets (P<0.05). There was no difference in survival among treatments when fish were fed at 17°C. At the higher temperature, the fish fed the menhaden oil and the mixed oil diets had equal or higher weight gains than the other dietary treatments in both experiments; there was no difference in weight gain among treatments at the lower temperature. The reduced resistance to infection by channel catfish fed menhaden oil or linseed oil at the high temperature may be caused by the competitive inhibition of arachidonic acid metabolism by n−3 fatty acids as occurs in warm-blooded animals. A combination of menhaden oil and corn oil, or sources of n−3 highly unsaturated fatty acids and linoleic acid, appear to be desirable in practical catfish feeds to optimize immunocompetence and growth.

Comparison of satiate feeding and restricted feeding of channel catfish with various concentrations of dietary protein in production ponds

Abstract A 2 × 3 factorial experiment was conducted with channel catfish (Ictalurus punctatus) using satiate or restricted feeding with 26, 32 or 38% dietary protein concentrations in practical catfish diets. The diets were similar to commercial catfish feeds, with major ingredients being soybean meal, ground corn, fish meal and wheat middlings, and small amounts of vitamin and mineral supplements. The protein concentration of the diets was increased by substituting a fixed ratio of soybean meal to fish meal (5 : 1) for corn. Essential amino acids in all diets were adequate. Energy concentration of the diets was not regulated. Fish were grown from 60 g to marketable size at a stocking density of 13 590 fish per ha in 400-m2 earthen ponds. Fish in the satiation feeding group were fed as much as they would consume each day for the 125-day spring-summer experimental period. Fish in the restricted feeding group were not fed more than 60 kg/ha day−1; this rate was reached at approximately day 70 of the experiment. There was a significant interaction between feeding regime and dietary protein concentration on weight gain. Weight gain of fish fed to satiation decreased linearly as dietary protein content increased, while weight gain of fish under restricted feeding increased linearly with increasing dietary protein percentage. Weight gain of fish fed to satiation was positively correlated with feed consumption, which decreased linearly as dietary protein concentration increased. Dietary protein concentration had no influence on feed conversion under satiate feeding, but had a positive effect on feed conversion under restricted feeding. Feed conversion of fish fed to satiation was higher than that of fish under restricted feeding. Dietary protein had a quadratic effect on dressing percentage; it increased as dietary protein increased from 26 to 32% and decreased as dietary protein increased from 32 to 38% for both satiate and restricted feeding. Body fat content of fish in both feeding regimes was negatively correlated with the protein/digestible energy ratio of the diets. Body fat content of fish fed to satiation was higher than that of fish fed at the restricted rate. These results indicate that feeding rate significantly influences weight gain and body composition of channel catfish. In addition, channel catfish can obtain sufficient nutrients from a 26%-protein, amino-acid-balanced practical diet for maximum weight gain with satiate feeding, but when fed to less than satiation higher-protein diets are required.

Digestive Enzyme Activities in Striped Bass from First Feeding through Larva Development

Abstract Growth and activities of the digestive enzymes trypsin, chymotrypsin, carboxypeptidase A, α-amylase, and pepsin in striped bass Morone saxatilis were measured from the day before the fish first accepted food (day 4) to near the end of larva development (day 32). Fish were fed either live brine shrimp nauplii Artemia sp. (BSN), heat-killed BSN, or a prepared diet designed to be nutritionally complete with satisfactory physical and palatability properties. The larvae consumed the prepared diet but did not grow and all larvae fed this diet died soon after day 16. Larvae fed live or heat-killed BSN grew satisfactorily but growth of fish fed live BSN was faster (P < 0.05). With the exception of pepsin, which was not found until day 16, all of the measured enzymes were present in the digestive tract at the time of first feeding and activities of these enzymes were 25 to 60% of those at day 32, For the first 12 d, specific activity of the enzymes was not influenced by growth or diet. Near day 16, enzyme...

Dietary Phosphorus Requirement of Channel Catfish (Ictalurus punctatus)

Abstract When channel catfish fingerlings were fed semipurified diets supplemented with monobasic sodium phosphate, their minimum requirement of dietary phosphorus for satisfactory growth and bone mineralization was approximately 0.45%. The addition of calcium (calcium carbonate) to a phosphorus-supplemented diet increased growth rate slightly but not significantly. Availability of phosphorus for channel catfish, as determined by net absorption from the digestive tract, was 90-94% for monosodium and monocalcium phosphate, 65% for dicalcium phosphate (feed-grade), 40% for fish meal, 50-54% for soybean meal, and 25-28% for cereal products.

Identification of feed enhancers for juvenile largemouth bass Micropterus salmoides

Abstract Three trials were performed to identify feed enhancers for largemouth bass. Fish trained on dry pellets were stocked into 45 1 aquaria. Trial 1 evaluated the palatability of diets in which fish meal (FM) was replaced with 0, 20, 40, and 60% soybean meal (SM-00, SM-20, SM-40 and SM-60). Feed intake declined as dietary concentration of soybean meal increased ( P Euphasia pacifica ) extract. Chemical groups were tested alone or in all possible combinations. Nucleotides alone enhanced feed intake of fish by 46% compared with the control diet ( P P > 0.05). No additive effects among chemical groups were observed ( P > 0.05). In trial 3, inosine and IMP-5′ were tested alone at 1400, 2800, and 5600 mg kg −1 of feed or together, each at 2800 mg kg −1 of feed. A diet with 10% fish meal (FM-10) was also evaluated. Effective dietary concentration of IMP-5′ seems to be about 2800 mg kg −1 of feed which gave a feed intake 23% higher than the control diet ( P −1 of feed failed to further increase feed intake ( P > 0.05). Inosine was not an effective feed enhancer at the dietary levels tested ( P > 0.10). No significant additive effect of inosine in a diet flavored with IMP-5′ at 2800 mg kg −1 of feed was found ( P > 0.10). Feed intake was highest for fish fed FM-10 ( P

Available phosphorus requirements of food-size channel catfish (Ictalurus punctatus) fed practical diets in ponds

A pond feeding experiment was conducted in which Year 2 channel catfish (average initial weight, 61 ± 5 g) were stocked in 400 m2 earthen ponds (13950 fish ha−1) and fed an all-plant extrusion processed commercial type diet that contained 0.20, 0.27, 0.36, 0.44 and 0.60% available phosphorus from plant ingredients and monosodium phosphate. Availability of phosphorus in the basal diet and monosodium phosphate was determined by digestibility (net absorption) trials. All diets contained an inorganic calcium:available phosphorus ratio of 1:1. Each diet was fed to fish in four replicate ponds once daily to satiation throughout a 140 day growing season. Data for weight gain, feed conversion ratio, dressing percentage, serum phosphorus, serum alkaline phosphatase activity, bone ash, bone phosphorus, bone breaking strength, muscle composition and visceral fat were subjected to regression analysis to determine effects of the dietary levels of available phosphorus on these responses. There was no significant effect (P > 0.10) of increasing dietary available phosphorus on weight gain, feed conversion, and dressing percentage. Serum phosphorus, bone ash, bone phosphorus, fat, moisture and protein contents of muscle and visceral fat showed significant linear responses (P < 0.06) and serum alkaline phosphatase activity and bone breaking strength showed significant quadratic responses (P < 0.04) with increasing concentrations of dietary available phosphorus. Broken-line analysis showed that maximum serum alkaline phosphatase activity and bone breaking strength were obtained at dietary available phosphorus concentrations of 0.25 and 0.31%, respectively. Data from this study indicated that an all-plant, commercial type diet with no phosphorus supplement, containing 0.20% available phosphorus, was sufficient for maximum weight gain by channel catfish grown to marketable size in ponds. Based upon alkaline phosphatase activity and bone strength, 0.3% available phosphorus is recommended for production diets for catfish grown in ponds. Increasing the dietary available phosphorus to higher concentrations appears to reduce muscle and visceral fat in intensively-fed, pond-grown channel catfish.