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In three studies on the effects of frequency of feeding on channel catfish (Ictalurus punctatus), optimal growth and food efficiency were obtained from groups fed to satiation two times per day. Gains in weight were substantially reduced in groups fed only one time per day and were not enhanced by feeding four times per day. The fact that food efficiencies were similar in fish fed one, two, and four times per day indicated that food intake and not utilization was the growth limiting factor. In a study with automatic feeders, fish fed 24 times per day had significantly poorer gains and food efficiencies than those fed four or eight times per day.

Two studies were conducted with channel catfish fry (Ictalurus punctatus) fed diets containing four levels of pantothenic acid activity (10, 25, 66, and 250 mg/kg diet). Supplemental pantothenate markedly improved growth rate, survival, and feed conversion, and prevented a loss of appetite, clubbed gills, and sluggishness. The results of these experiments suggest that diets fed to catfish fry should contain at least 250 mg of pantothenic acid per kg of diet.

Several experiments were conducted on relationships between oxygen consumption of channel catfish (Ictalurus punctatus) and environmental dissolved oxygen concentrations, feeding status, weight of fish, and temperature. Estimates of oxygen consumption under culture conditions were obtained by determining the rate of oxygen depletion in a still tank without aeration. Respiratory dependence (decrease in oxygen consumption rate with a decrease in environmental oxygen concentration) in both well-fed and fasted fish was noted at oxygen concentrations between 1 and 7 milligrams/liter. The oxygen consumption rates obtained one hour after feeding were higher than those taken immediately after feeding or from fasted fish. A log-log relationship between oxygen consumption and body weight of fish (2.3-1,006 g) was demonstrated. The slope (b) for the equation, oxygen consumption = (a) (weight)bwas 0.80 for both well-fed and fasted fish. The relationship between oxygen consumption and environmental temperature was linear over the range 24-28 C for well-fed fish and 24-30 C for fasted fish. The Q10's for plots for the well-fed and fasted fish were 1.9 and 2.3, respectively; thus the data were in accord with van't Hoff's Law.

Data on body weight, five body measurements, dress-out weigbt, and lipid content were collected from 56-week old channel catfish, Ictalurus punctatus, which belonged to 18 full-sib families. Analyses of variance showed that: (1) all sex differences, except that in dressing percentage and lipid content, were significant (P < 0.01); (2) the sex component of variance in percent of total variance ranged from 0.0% for lipid content to 34.7% for interorbital width; (3) all family differences were significant (P < 0.01), while those between replicate tanks were insignificant (P > 0.05); (4) differences between families or individual fish contributed most to total variance while those between tanks and family X tank interactions contributed least; (5) in all characters observed, the family component of variance ranged from 12.6% (dress-out %) to 49.2 % (head length) of total variance. Dress-out weight was positively and highly correlated with body weight, body measurements, or head weight (r= 0.89 or more). The correlations between percent dress-out and these characters were medium or small (r = 0.25-0.54). With the exception of percent head weight, all other characters had medium or small correlations with lipid content (r = 0.15-0.49). Percent head weight was negatively but moderately correlated with dress-out weight, dress-out percentage, and lipid content.

In 20 and 12 week feeding trials, channel catfish fingerlings were fed purified diets containing five levels (0, 5, 10, 20, and 30 mg/kg) and six levels (0, 1, 2, 5, 10, and 20 mg/kg) of supplemental pyridoxine hydrochloride. Fish fed unsupplemented diets (pyridoxine content of 1.2 mg/kg) were characterized by anoxeria, nervous disorders, tetany, greenish-blue body coloration, and eventual mortality. Anemia, which has been reported in pyridoxine deficient salmonids, was not observed in pyridoxine deficient catfish. However, a microcytic, normochromic anemia was observed in groups fed high dietary levels of pyridoxine (20 mg/kg or greater). The dietary pyridoxine level required for maximal growth was approximately 3 mg/kg of diet. All other deficiency signs were prevented by 2.2 mg/kg of diet.

Purified diets with five levels (25, 50, 75, 100, and 200 mg/kg) of supplemental L-ascorbic acid (LAA), and equimolar levels of ethylcellulose coated L-ascorbic acid (EAA) and dipotassium L-ascorbate 2-sulfate dihydrate (AS) were pelleted and fed to 7.9 ± 0.2 g channel catfish fingerlings for 20 weeks. A dietary level of 25 mg/kg of all three forms of vitamin C prevented spinal abnormalities. Approximately 50 mg/kg diet of either LAA or EAA was sufficient for maximal growth and feed efficiency. Growth response to AS was similar to a Michaelis-Menten type curve and 200 mg/kg diet of AS was necessary to achieve maximal growth. Blood and liver ascorbic acid levels were positively correlated with supplemental levels of LAA, EAA, and AS up to 200 mg/kg; however, blood and liver ascorbic acid levels of fish fed AS were considerably less than those fed LAA and EAA. Weight gains were positively correlated with blood ascorbate levels up to 7 µg/ml. No measurable level of AS was detected in blood or liver. These results suggest that the rate of enzymatic hydrolysis of AS to LAA or rapid excretion of AS may have been the limiting factor.

Channel catfish fingerlings were fed purified diets containing five levels (0, 20, 40, 80, and 120 mg/kg) and six levels (0, 3, 8, 20, 40, and 80 mg/kg) of riboflavin in separate 20 and 12 week feeding studies. The dietary riboflavin level required to provide maximal growth in channel catfish fingerlings was found to be approximately 9 mg/kg of diet. All fish fed unsupplemented diets (riboflavin content less than 0.1 mg/kg diet) demonstrated a short body dwarfism which was the result of arrested longitudinal growth of the vertebrae. This abnormality did not occur in groups fed 3 mg/kg or higher levels of riboflavin. No histological abnormalities were recognized in the liver, kidney, lateral muscle, gastrointestinal tract, gills, or bones of deficient fish. J. Nutr. 108: 1512-1517, 1978.

Channel catfish fingerlings were fed purified diets containing five levels (0, 25, 50, 100, and 150 mg/kg) and six levels (0, 5, 10, 25, 50, and 100 mg/kg) of supplemental niacin in 20 and 12 weeks feeding studies, respectively. The dietary niacin level required to provide maximal growth in rapidly growing channel catfish fingerlings was found to be approximately 14 mg/kg of diet. Fish fed unsupplemented diets (niacin content of 1.6 mg/kg diet) demonstrated poor growth, anemia, skin and fin lesions and hemorrhages, exophthalmia and total mortality in 20 weeks. Mortality and gross deficiency signs were prevented by 11.6 mg niacin/kg diet and anemia was prevented by 6.6 mg/kg. No histological abnormalities were observed in the heart, hepatopancreas, kidney, lateral muscle, gastrointestinal tract and gill tissues of deficient fish. J. Nutr. 108.- 1508-1511, 1978.

In separate 20 and 12 week feeding studies, channel catfish fingerlings were fed semipurified diets containing five levels (0, 2.5, 5.0, 10.0 and 15.0 mg/kg) and six levels (0, 0.5, 1.0, 2.5, 5.0 and 10.0 mg/kg) of supplemented thiamin hydrochloride respectively. The dietary thiamin level required to provide maximal growth and prevent deficiency symptoms in channel catfish fingerlings was found to be approximately 1 mg/kg of diet. Fish fed unsupplemented diets (thiamin content of less than 0.1 mg/kg diet) demonstrated anorexia, extremely poor growth, dark coloration of the skin and increased mortality rates. Neurological symptoms were not observed. Histological examinations of the heart, hepatopancreas, kidney, lateral muscle, gastrointestinal tract and gills of deficient fish revealed no abnormalities.

Linoleate, linolenate, arachidonate, docosahexaenoate and six other fatty acids were major components of 24 ester preparations fed as 5% of the diet for 60 days to groups of male white rats. The experiment was designed so as to provide that all major fatty acid components were independent of each other in the sense that the intake of each was poorly correlated with the intake of any of the others. Fatty acid compositions of liver lipids were determined and were related to the composition of the diet lipids. Linolenate and docosahexaenoate contents of diet and tissue revealed the same relationships reported previously from experiments in which individual pure acid esters were added to a fat-free diet. Linoleate, when fed in lipid mixtures, was more effective in raising the linoleate concentration in liver lipids than when fed alone, but this increase did not change the shape of the dose-response curve or the estimated nutritional requirement. Large amounts of fish oil in the diet tended to depress the arachidonate concentration in tissue lipids.

A study was conducted on the effects of three dietary levels of animal fat (5%, 10%, and 15%) and two environmental temperatures (23 and 28°) on the digestible energy (DE) and apparent absorbability (AA) of animal fat in diets of 150 g catfish. Results obtained by the use of the chromic oxide indicator technique demonstrated that at 28° and substitution levels up to 10% of diet, animal fat had a DE value of 7,000 kcal/kg and an AA of 94%. At the 15% level of substitution, both DE and AA were substantially reduced. At each level of substitution, DE and AA values were considerably lower in fish reared at 23°. At supplemental levels up to 10% of diet, the DE and AA values for catfish at 23° were 6,130 kcal/kg and 70%, respectively. Results from this study reconfirmed previous growth data which indicated that animal fat is an excellent dietary energy source for catfish which are reared at optimum temperatures.

Semipurified diets with casein as the sole protein source were supplemented with gelatin, arginine, cystine, methionine or tryptophan, and fed to channel catfish (Ictalurus punctatus) fingerlings. Increasing the arginine level from 1.1% to 1.7% of diet by the isonitrogenous substitution of gelatin for casein resulted in a significant enhancement of growth. However, the addition of free arginine, cysteine, tryptophan or methionine to casein had little effect on growth or food conversion. These data substantiate a previous report that suggested catfish were similar to carp in their inability to utilize free amino acids.

Studies were conducted to determine the effects of several lipid supplements in practical-type diets for channel catfish (Ictalurus punctatus) fingerlings reared at 23° and 28°. Maximum growth and feed efficiency were obtained when diets were supplemented with 9% animal tallow, 9% menhaden oil or a combination of the two (4.5% of each). A growth suppression was observed when fish were fed a diet containing a combination of 3% corn oil, 3% animal tallow and 3% menhaden oil. In studies on interactions of dietary protein and lipid at 23° and 28°, increasing dietary protein from 25% to 35% resulted in higher gains. At 28°, increasing dietary lipid from 5% to 12% resulted in increased gains with diets containing 35% protein but not with diets containing 25% protein. At 23°, 5% lipid was sufficient in all cases. Carcass lipid levels increased with increasing temperature and were positively correlated with weight gains and negatively correlated with carcass moisture content. Improved protein conversion (protein fed:protein gained) was noted when dietary protein levels were increased from 25% to 35%; when dietary lipid levels were increased from 5% to 12%; and when environmental temperature was increased from 23° to 28°.

Eight saturated fatty acid esters were fed to male white rats for 30 days in a 1/81 fractional factorial experiment in which diets contained 12–38% of their total energy as lipid. Marked increases in food intake, feed efficiency, and weight gain were achieved when lipid provided 36% of diet energy, and when that lipid was more than half caproate, caprate, myristate, and/or stearate. Caproate was the only saturated fatty acid to increase the concentration of cholesterol in plasma and liver. Caproate also increased plasma glucose levels. The feeding of stearate or caprylate decreased plasma and liver cholesterol. Caprate increased liver fat. The short-chain fatty acids (butyrate to myristate) increased the concentration of fat in the carcass.

Three feeding studies on the vitamin C requirements of channel catfish were conducted with practical and semipurified diets. In a long-duration study in which fish achieved almost a 4,000% increase in weight, 50 mg of l-ascorbic acid/kg diet was required for maximal growth and food efficiency. A diet stability study revealed that excessive losses in activity of l-ascorbic acid occurred when practical diets were stored for 16 weeks at 20°. The typical scoliosis condition associated with severe vitamin C deficiency in fish occurred in the nonsupplemented groups in the study with practical diets. Severe growth reductions were obtained from fish fed nonsupplemented semipurified diets, yet no incidences of spinal abnormalities were noted.

A 3 × 3 × 2 factorial feeding study with channel catfish (Ictalurus punctatus) included the following dietary treatments: 0, 25, and 100 mg/kg dl-α-tocopherol; 0, 10, and 100 g/kg oxidized menhaden oil; and 0 and 125 mg/kg ethoxyquin. Fish fed diets containing oxidized menhaden oil without supplemental α-tocopherol or ethoxyquin exhibited poor growth, food conversion, and survival rates; high incidence of three distinct gross syndromes—exudative diathesis, muscular dystrophy, and depigmentation; fatty livers; anemia; and pronounced histological changes in muscle fibers, kidney, and pancreatic tissue. Although these conditions were improved by the addition of either α-tocopherol or ethoxyquin, analysis of variance of data revealed differentiation in effects. Tocopherol had a very strong main effect on all variables; yet, ethoxyquin did not have a significant effect (P> 0.05) on hematocrit levels and incidences of muscular dystrophy. Growth reduction, hematological changes, and the occurrence of muscular dystrophy and fatty livers were not observed in fish fed diets without oxidized menhaden oil, α-tocopherol, or ethoxyquin. However, high incidences of exudative diathesis, depigmentation, and mortality were present in this dietary treatment. Data from this study suggest that 25 mg/kg α-tocopherol and 125 mg/kg ethoxyquin, or 100 mg/kg α-tocopherol should provide adequate protection in most practical catfish diets.

Four feeding studies were conducted to determine to what extent soybean meal could be used to replace fish meal in diets for channel catfish (Ictalurus punctatus). When soybean meal was substituted on an isonitrogenous basis for menhaden meal, growth and feed efficiency were substantially reduced (P< 0.05). Gains were not enhanced when synthetic methionine, cystine or lysine, the most limiting amino acids as the results of this substitution, were added to the soy-substituted diets. When diets void of fish meal were supplemented with a lipid extract, nonlipid residue or ashed fraction of menhaden meal, growth and food conversion data revealed that the growth factors not provided by soybean meal were in the nonlipid residue of menhaden meal and were destroyed by ashing. A further study demonstrated that these factors were not polar lipids that could be removed by extraction with chloroform-methanol (2:1). These data suggested that the growth factors were in the protein fraction of menhaden meal but do not explain why growth responses were not obtained when the soy-substituted diets were supplemented with the most limiting amino acids.

Channel catfish (Ictalurus punctatus) fingerlings were reared in 1-m-diameter fiberglass tanks at 26° and fed 27 experimental diets differing in source of lipid. Duplicate groups of fish were fed each of eight primary lipid sources and each lipid was fed at a level of 10% of diets in three molecular forms: triglyceride, free fatty acid, and ethyl ester. Highest average weights occurred when the fish were supplemented with beef tallow, olive oil and menhaden oil triglycerides. Substantially lower gains were obtained from groups fed short- and medium-chain fatty acids, a fat-free diet, safflower oil (high in 18:2ω6) and linseed oil (high in 18:3ω3). In general, triglyceride and ethyl ester diets led to more rapid growth of channel catfish than did free fatty acid diets. Food conversions for fish fed triglyceride diets were superior to those of fish on the other two dietary lipid types. The deposition of fatty acids in whole carcasses followed very closely the fatty acid composition of the diet whereas deviation from the dietary fatty acid composition was noted in liver.

The long-term effects of three levels of dissolved oxygen (100, 60 and 36% of air saturation) on channel catfish, Ictalurus punctatus, were evaluated under two feeding regimes—a constant rate of 3% of biomass daily and ad libitum. At ad libitum rates (6-week duration) average gains of 159, 124, and 65 g per fish were obtained in tanks containing oxygen at 100, 60 and 36% of saturation, respectively. In both experiments food consumption and efficiency were drastically reduced at 36% oxygen saturation. Survival rates were 100% in all groups, thus suggesting that disease and parasite problems were not enhanced by a hypoxic environment. In these studies catfish did not demonstrate a polycythemic response to hypoxic conditions.

A study of the interaction of five environmental temperatures (20, 24, 26, 30 and 33°), and three types of dietary lipids (beef tallow, safflower oil, and menhaden oil) on the growth and body composition of channel catfish, Ictalurus punctatus, indicated that maximum growth was obtained at 30° for fish fed each lipid supplement for a 70-day experimental period. At all temperatures, higher gains were obtained from beef tallow and menhaden oil than safflower oil supplements; likewise, lower food conversion rates were obtained from beef tallow and menhaden oil. The lipid level in fish carcasses increased with increasing temperatures up to 30° for all dietary supplements. At the optimum temperature for growth (30°), fish fed beef tallow contained less lipid than those fed the other supplements. The fatty acid composition of the diets was reflected in both liver and carcass lipids.

Diets with 25 or 35% protein and various corn and fat levels were fed to satiation (ad libitum) and at a controlled rate to 14- and 114-g channel catfish (Ictalurus punctatus). Growth and feed conversion criteria demonstrated that larger fish require lower levels of protein and higher levels of energy than smaller fish. For 114- to 500-g fish 25% protein was adequate but for 14- to 100-g fish, 35% protein produced the faster gains. Corn (up to 25%) and fat (up to 12%) were equally effective as energy sources with digestible energy values of 2,700 and 6,780 kcal/kg, respectively. High dietary levels of protein and energy resulted in decreased feed consumption. Feed intake (% body weight/day) decreased from 5% for 114-g fish to 2% for 500-g fish. Body composition was influenced by ratio of dietary digestible energy to protein (DE/P). Protein deposition remained independent of diet while body moisture levels were negatively correlated and body fat levels were positively correlated to DE/P ratios. Effects of DE/P ratios on body composition of channel catfish were similar to those reported for the chicken but the magnitude of the effects was not as great for catfish as reported for chickens.

Channel catfish (Ictalurus punctatus) fingerlings were fed diets containing varying dietary levels and ratios of calcium (0.5 to 2.0%) and phosphorus (0.5 to 1.2%). Results from two studies indicated that the available phosphorus requirement of catfish is approximately 0.8% of diet. In both experiments gains were maximal in fish fed diets containing 1.5% calcium and were reduced when higher levels were fed. This hypercalcemia effect could not be prevented by adjusting the Ca/P ratio by the addition of phosphorus to the diet. A phosphorus deficiency characterized by reduced growth, poorer food efficiency and lower bone ash and hematocrit levels occurred in fish fed 0.5 or 0.6% available phosphorus. The absence of a growth response to 0.4% supplemented phosphorus in the form of calcium phytate suggested that catfish are not able to fully utilize phytin phosphorus. Bone ash values from skull and vertebrae samples indicated that the calcium requirement for maximal bone mineralization may be higher than that for optimal growth.