Effect of rainbow trout growth hormone complementary DNA on body shape, carcass yield, and carcass composition of F1 and F2 transgenic common carp (Cyprinus carpio).

The effect of rainbow trout growth hormone complementary DNA on body shape, dress-out yield, and body composition were assessed in the F1 and F2 generations of transgenic common carp (Cyprinus carpio). All measurements were compared with those for nontransgenic full-sibling common carp in their respective families, and the fish were communally evaluated in earthen ponds. The body weight and length were highly correlated (P <0.01) in both genotypes in all the families. Head morphometrics were negatively correlated (P <0.05) to weight and length of the fish. Various head, body, and caudal traits grew disproportionately faster in transgenic fish in both generations. The altered body shape of transgenic fish resulted in improved dressing percentage in the F2 generation. The carcass composition of transgenic muscle had a lower percentage of (P <0.01) moisture and lipids and higher (P <0.01) percentage of protein in both generations. Six of the 18 amino acids analyzed in F1 transgenic common carp muscle were higher F1 (P <0.05) than the control genotype; however, amino acid ratios were minimally changed. Also, the fatty acid profiles of both genotypes were minimally altered. Higher histidine and lysine ratios in the diet are recommended for maximum growth and health of transgenic common carp in intensive culture systems on the basis of essential amino acid ratios.

Dietary folate requirement determined for channel catfish, Ictalurus punctatus.

Juvenile channel catfish, Ictalurus punctatus, were fed semipurified basal diets containing 0, 0.2, 0.5, 1.0, 4.0 or 10.0 mg/kg of folic acid or 10 g/kg of succinylsulfathiazole in aquaria for 15 wk. Fish fed the sulfonamide showed higher mortality, lower weight gain, lower thrombocyte counts, higher hemocytoblast and neutrophil counts, and lower liver folate concentrations than did control fish (0 folic acid), indicating that significant intestinal bacterial synthesis of folate occurs in channel catfish. There were positive quadratic regressions of weight gain, hematocrit, erythrocyte and leukocyte numbers, and positive linear regressions of plasma and liver folate on dietary folic acid concentrations. Broken-line analysis showed that the dietary requirements for folic acid for optimum weight gain, hematocrit, and erythrocyte and leukocyte numbers were 1.01, 1.17, 1.12 and 1.15 mg/kg, respectively. Plasma and liver concentrations of folate associated with normal growth and hematopoiesis were 22.9 nmol/L and 20.0 nmol/g, respectively. Ratios of leukocytes and lymphocytes to erythrocytes were maximal in fish fed 4.0 mg folic acid/kg, indicating that immunocompetence may increase as the dietary dose exceeds that required for normal growth. Anemia in folate-deficient channel catfish was characterized by pale livers, spleens, gills and kidneys, and by poikilocytosis, anisocytosis, pyknosis, cytoplasmic clearing, increased numbers of hemocytoblasts, macrocytosis, and binucleated erythrocytes or "spectacle" cells.

Influence of large doses of ascorbic acid on performance, plasma calcium, bone characteristics, and eggshell quality in broilers and Leghorn hens.

Four experiments were conducted using broilers (Experiments 1 and 2) or White Leghorn hens (Experiments 3 and 4) to determine the effects of large doses of dietary ascorbic acid on performance, plasma concentration of total and ionic calcium, bone characteristics, and eggshell quality. A total of 564 male broilers were fed diets containing ascorbic acid (ranging from 0 to 3,000 ppm) from 3 to 7 wk of age. Weight gain and feed conversion were measured, and blood plasma was analyzed for total and ionic calcium. Leg bones (femur, tibia, and metatarsus) were analyzed for bone mineral content, density, and breaking strength. In Experiments 3 and 4, a total of 484 Leghorn hens were fed diets containing ascorbic acid (ranging from 0 to 3,000 ppm) for 4 wk. Egg weight and specific gravity were determined, and plasma and tibiae were analyzed as in Experiments 1 and 2. Results of the broiler experiment (Experiment 2) indicated that plasma ionic calcium was significantly increased (P < .05) in ascorbic-acid-treated birds. Among leg bones examined, femur strength was improved by 16% in birds fed 2,000 ppm of ascorbic acid (Experiment 2). Other bone characteristics were not affected. In the layer experiments (Experiments 3 and 4), egg weight increased up to 5% and egg specific gravity was improved in hens fed 2,000 or 3,000 ppm of ascorbic acid, which also had increased calcium in the blood. Results suggest that large doses of ascorbic acid in the diet influence calcium metabolism, affecting bone and eggshell mineralization in chickens.

Nutrition of aquaculture species.

Dietary requirements for amino acids and fatty acids have been reported for channel catfish (Ictalurus punctatus), salmonids (Oncorhynchus spp.), common carp (Cyprinus carpio), tilapias (Oreochromis spp.), and eel (Anguilla japonicus). Most of the vitamin and mineral requirements are available for channel catfish and salmonids, and some are available for common carp, tilapia, eel, and other finfish and crustaceans. From this available information, cost-effective feeds can be formulated for the major commercial aquaculture species. Major differences in nutrient requirements between fish and mammals or birds are as follows: fish have a lower digestible energy:protein ratio (8 to 10 kcal of DE/g of CP for fish vs 15 to 20 kcal of DE/g of CP for livestock); fish require n-3 fatty acids and land animals require n-6; fish can absorb minerals from the water, which negates the need for some minerals in the diet; and fish have limited ability to synthesize vitamin C and must depend on a dietary source. Areas for further research include 1) refinement of nutrient requirements of the major culture species considering effects of fish size, temperature, and management; 2) nutrient requirements of crustaceans; 3) effects of nutrition on fish health and product quality; and 4) feeding technology.

L-ascorbyl-2-monophosphate has equal antiscorbutic activity as L-ascorbic acid but L-ascorbyl-2-sulfate is inferior to L-ascorbic acid for channel catfish.

Channel catfish (Ictalurus punctatus) fingerlings (13 g average initial weight) were fed semipurified diets supplemented with 0, 0.06, 0.12, 0.24 and 0.72 mmol/kg (0, 11, 22, 44 or 132 mg/kg) of ascorbic acid molar equivalent supplied by either L-ascorbic acid, L-ascorbyl-2-monophosphate (Mg salt) (AAP), or L-ascorbyl-2-sulfate (K salt) (AAS). After 14 wk, weight gains were equal for all fish fed diets containing L-ascorbic acid or AAP; however, growth rates were less for fish fed AAS at all dietary levels and for fish fed the ascorbic acid-free diet (control). There were no gross signs of vitamin C deficiency in any of the fish fed L-ascorbic acid or AAP, whereas spinal deformities were found in the controls and in fish fed all but the highest concentration of AAS. The percentage of spinal deformities decreased as dietary levels of AAS increased. Reduced bone collagen content and histopathology in liver and gill tissues also indicated ascorbic acid deficiency in the controls and in fish fed all but the highest concentration of AAS. Limited histopathology was found in fish fed the lowest level of L-ascorbic acid but not in those fed the lowest level of AAP. Regression analysis of weight gain data showed that the vitamin activity of ascorbic acid from AAS was only 5.2% of that from L-ascorbic acid for growth. This study indicates that AAP has equimolar activity to L-ascorbic acid as a vitamin C source for channel catfish and that AAS has vitamin activity for this species but at a much lower level than the other compounds.

Amino acid requirements for growth of Nile tilapia.

A series of feeding experiments was conducted in aquaria to determine the quantitative requirements of the 10 essential amino acids for growth of young Nile tilapia (Oreochromis niloticus). The test diets contained casein and gelatin supplemented by crystalline L-amino acids to provide an amino acid profile similar to 28% whole egg protein except for the test amino acid. Each set of test diets consisted of seven isonitrogenous diets containing varying levels of the amino acid to be tested. Weight gains analyzed by the broken line regression method indicated the following requirements as a percentage of the dietary protein: lysine, 5.12; arginine, 4.20; histidine, 1.72; valine, 2.80; leucine, 3.39; isoleucine, 3.11; threonine, 3.75; tryptophan, 1.00; methionine with cystine (0.54% of the protein), 3.21; and phenylalanine with tyrosine (1.79% of the protein), 5.54.

Elevated levels of dietary ascorbic acid increase immune responses in channel catfish.

Channel catfish fingerlings were fed purified diets containing 0 to 3000 mg/kg of ascorbic acid until external signs of scurvy were seen in the fish fed the ascorbic acid-deficient diet. At this time, resistance to bacterial infection, antibody production, complement activity and phagocytic activity were assessed for fish from the various dietary treatments. Mortality rates of fish experimentally infected with Edwardsiella ictaluri, the bacterium causing enteric septicemia in channel catfish, decreased with increases in dietary ascorbic acid doses, ranging from 100% for fish fed the ascorbic acid-deficient diet to 15% for fish fed 300 mg ascorbic acid per kilogram diet and 0 for fish fed 3000 mg ascorbic acid per kilogram diet. Antibody response to E. ictaluri antigen, hemolysis of sensitized sheep erythrocytes by complement activity and phagocytic engulfment of E. ictaluri by peripheral phagocytes were each impaired in fish fed the diet without supplemental ascorbic acid; intracellular bactericidal activity of the phagocytes was not affected by ascorbic acid deficiency. There were no differences in antibody production, complement activity, or phagocytic activities among fish fed diets containing 30-300 mg ascorbic acid/kg of diet. However, the dose level of 3000 mg ascorbic acid/kg significantly enhanced antibody production and complement activity.

Biotin supplementation of practical diets for channel catfish.

A purified diet and two practical-type diets were each evaluated with supplemental biotin (1 mg/kg), without supplemental biotin, and with a biotin antagonist (freeze-dried egg white) for channel catfish (Ictalurus punctatus) over a 17-week feeding period. Omission of supplemental biotin from the casein-dextrin purified diet, with or without egg white, resulted in anorexia, reduced growth rate, lighter skin, hypersensitivity and reduced liver pyruvate carboxylase activity by this fish. Omission of supplemental biotin from either practical diet, one containing basically soybean meal and corn and another containing basically soybean meal, corn and menhaden fishmeal , caused none of these deficiency signs. The ratio of biotin to indigestible dry matter in feces was lower than that in the diet for all fish, indicating little or no synthesis of biotin by the intestinal microflora in channel catfish. Levels of total biotin, measured microbiologically, in the all-plant and in the plant- fishmeal diets were 0.37 and 0.33 mg/kg, respectively. These results indicate that practical diets for channel catfish made from the commonly used ingredients, soybean meal, corn and menhaden fishmeal , do not need supplemental biotin.

Requirement for alpha-tocopherol by channel catfish fed diets low in polyunsaturated triglycerides.

Channel catfish (Ictalurus punctatus) were grown from 5 to 45 g average size by feeding diets containing a low level of polyunsaturated fatty acids (0.48% linolenic acid) and supplemented with 0 (basal), 25, 75, 250 or 2500 mg/kg of alpha-tocopherol or 125 mg/kg of ethoxyquin. Growth rate was improved by supplementation of the basal diet with ethoxyquin (P less than 0.05) and further improved by supplementation with alpha-tocopherol (P less than 0.05); increasing alpha-tocopherol above the lowest level did not improve growth. Fish fed the basal diet were lighter in color, visibly thinner across the back, more easily excitable and had lower hematocrits. Histological signs in the alpha-tocopherol-deficient fish included extreme atrophy and necrosis of white muscle fibers, sclerotic glomeruli in the posterior kidney and ceroid-laden macrophages in intrahepatic blood vessels. Fish fed the lowest level of alpha-tocopherol showed no gross signs of vitamin deficiency but histological examination revealed necrosis of white muscle fibers and ceroids in liver blood vessels. No pathological changes were found in fish fed higher levels of alpha-tocopherol. These results indicate that high amounts of polyunsaturated fatty acids are not necessary in alpha-tocopherol-deficient diets to produce myopathy in channel catfish, and that the present National Research Council requirement for this vitamin for channel catfish may be low.

Intestinal synthesis and absorption of vitamin B-12 in channel catfish.

A feeding experiment conducted in a controlled environment and using a vitamin B12-deficient, but otherwise nutritionally complete, purified diet revealed that intestinal microorganisms in channel catfish synthesized approximately 1.4 ng of vitamin B12 per gram of bodyweight per day. Removal of cobalt from the diet or supplementation with an antibiotic (succinylsulfathiazole) significantly reduced the rate of intestinal synthesis and liver stores of vitamin B12. Radiolabeled vitamin B12 in the blood, liver, kidneys, and spleen of fish fed 60Co in the diet indicated that the intestinally synthesized vitamin was absorbed by the fish. The primary route of absorption was directly from the digestive tract into the blood because coprophagy was prevented in the rearing aquariums and the amount of vitamin B12 dissolved in the aquarium water was too low for gill absorption. Dietary supplementation of vitamin B12 was not necessary for normal growth and erythrocyte formation in channel catfish in a 24-week feeding period. A longer period, however, may have caused a vitamin deficiency since liver-stored vitamin B 12 decreased between the 2nd and 24th weeks.

Fish culture in the United States.

The culture of channel catfish, trout, and crayfish is a well-established, profitable enterprise, but aquaculture provides only a fraction of the protein consumed by Americans, who prefer red meat. This situation could change, since pond-raised fish require less energy for protein synthesis than land animals, the supply of ocean food fish no longer appears inexhaustible, and fish culture can utilize resources unsuitable for other agriculture.

Essentiality of biotin for channel catfish (Ictalurus punctatus) fed lipid and lipid-free diets.

A 3 X 2 factorial feeding study was conducted with channel catfish (Ictalurus punctatus) to evaluate effects of biotin, no biotin, or a biotin antagonist (avidin) in lipid and lipid-free diets. At 10 weeks, fish fed diets containing lipid were significantly larger than fish fed lipid-free diets. At 20 weeks, fish fed diets containing avidin had grown significantly less than those fed the other diets. At 22 weeks, fish fed the lipid diet supplemented with biotin had grown significantly more than those fed the lipid diet without biotin. Fish fed the lipid diet with avidin were found to be anemic and exhibited a marked depigmentation of the skin. Fish fed biotin in lipid and lipid-free diets had higher liver pyruvate carboxylase activity than fish fed diets without supplemental biotin. These results indicate that channel catfish require an exogenous source of biotin for maximum rates of growth and lipid utilization.

Pathology of the vitamin C deficiency syndrome in channel catfish (Ictalurus punctatus).

Channel catfish fingerlings fed purified diets devoid of vitamin C showed reduced growth rate, deformed spinal columns, external and internal hemorrhages, erosion of fins, dark skin color and reduced bone collagen content after 8 to 12 weeks, whereas fish fed a diet containing 30 mg/kg of vitamin C had none of these anomalies after 22 weeks. A dietary level of 30 mg of vitamin C per kg was insufficient to prevent distortion of gill filament cartilage, although 60 mg of vitamin C per kg was sufficient. Vertebral collagen percentages of 25 or below and liver ascorbic acid levels of 30 microgram/g or below appeared to be indicative of vitamin C deficiency in channel catfish fingerlings. Epidermis and dermis were almost completely healed and extensive collagen fiber formation had commenced in the somatic muscle, in experimentally inflicted wounds after 10 days in fish fed the vitamin C-free diet. Skin and muscle at the wound site were almost regenerated to normal after 10 days in fish fed 60 mg of vitamin C per kg of diet.