Andries J. Roem

Differing nutritional responses to dietary soybean meal in rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

This study was carried out to compare the responses of rainbow trout and Atlantic salmon to being fed defatted soybean meal. Two extruded experimental diets containing either low-temperature (LT)-fish meal as the sole protein ingredient or 32% fish meal and 30% soybean meal, were each fed to triplicate groups of 0.1 kg trout or 0.2 kg salmon maintained in 7°C freshwater. The experiment lasted 84 days, divided into three periods. Weight gain of the trout was similar with both diets, whereas the salmon gained 44% more weight with the fish meal diet than with the soybean meal diet. The apparent digestibilities were 6% higher for nitrogen, 8% higher for fat, and 11% higher for energy in the trout than in the salmon. The feed conversion ratio (FCR) was 24% lower, the nitrogen retention 34% higher, and the energy-retention 28% higher in the salmon than in the trout. Within each species, the digestibility of nitrogen was similar for both diets. In trout, the digestibilities of fat and energy were 4% higher, the nitrogen retention 8% higher, and the energy retention 9% higher with the fish meal than with the soybean meal diet. Similarly, but more severe within the salmon, the respective digestibilities of fat and energy were 16% and 9% higher, the nitrogen retention 19% higher, and the energy retention 23% higher with the fish meal than with the soybean meal diet. Both species developed enteritis in the distal intestine when fed the soybean meal diet.

Feed consumption and conversion in Atlantic salmon (Salmo salar) fed diets with fish meal, extracted soybean meal or soybean meal with reduced content of oligosaccharides, trypsin inhibitors, lectins and soya antigens

Abstract The objectives of the experiment were to examine palatability of diets containing two different soybean meals in Atlantic salmon ( Salmo salar ) previously fed fish meal diets, and to separate effects of feed intake and physiological factors in soybean meal on growth and feed conversion. A fish meal-based control diet (FM) and two diets with 40% of the protein from either toasted, extracted soybean meal (SBM), or soybean meal with reduced content of oligosaccharides and antinutritional factors (RO-SBM) were fed to 107-g salmon in seawater for 55 days. The fish were weighed at days 28 and 55, and feed consumption was monitored daily. The FM diet contained 100 mg kg −1 of the inert marker Y 2 O 3 , while the soybean meal diets contained 100 mg kg −1 of Yb 2 O 3 . During days 25–28, a feed preference and adaptation test was carried out. Salmon fed the FM diet were either fed equal amounts of the FM and SBM diets or the FM and RO-SBM diets. Fish previously fed the SBM or RO-SBM diets were fed equal amounts of the respective soybean diet and the FM diet. At day 28, preferences for the different diets were estimated by determining the relative proportion of Y and Yb in stripped faeces. At the end of the experiment, faeces were again stripped to determine digestibility of the diets. Both the SBM and the RO-SBM diets were readily accepted by S. Salar , as the fish consumed similar amounts of either of the two diets and the FM diet in the preference test. The daily feed consumption, measured as percent of body weight, was initially lower in the SBM fed fish, but was similar in all treatments during the last part of the experiment. Thus, the fish appeared to adapt to some factor in the SBM which did not notably affect palatability. Growth rate, feed conversion and digestibilities of nitrogen, fat and energy were lower in the salmon fed the SBM diet than the FM and RO-SBM diets, while they were similar in salmon fed the RO-SBM and FM diets. When feeding the SBM diet, a major reason for reduced feed conversion and, thereby, growth, appeared to be lowered digestibility of nutrients.

Long-term protein and lipid growth of Atlantic salmon (Salmo salar) fed diets with partial replacement of fish meal by soy protein products at medium or high lipid level

Abstract This study investigated long-term effects on nutrient digestibility and protein and lipid growth of soy protein and lipid levels used in commercial grower diets for Atlantic salmon. Two series of extruded diets were formulated to contain either 45% protein and 32% lipid (medium fat) or 40% protein and 39% lipid (high fat). Each series consisted of six diets in which a soy protein source partially replaced low-temperature (LT) dried fish meal (FM): FM only (control), soy protein concentrate (SPC, 30% of crude protein, CP); SPC added 0.2% dl -methionine (30% of CP, SPC+met); dehulled, defatted soybean meal (HP-SBM, 20% of CP); full-fat (FF) SBM (10% of CP), and; defatted SBM (10% of CP). Each diet was fed to triplicate groups of 0.56-kg salmon kept in sea pens. The experiment lasted 235 days, during which the salmon reached 2.5 to 2.8 kg. Growth was slower in the FM-control and HP-SBM treatments than in the other treatments. The HP-SBM diet induced enteritis in the distal intestine of the salmon and, at day 215, the apparent digestibilities of nitrogen, lipid and energy were lower in the HP-SBM treatments than in all other treatments. Except a slightly reduced muscle protein concentration in the HP-SBM treatment, no effects of dietary soy were detected on final body composition. Salmon fed the high-fat diets reached on average 122 g higher final weight than those fed the medium-fat diets; however, 91 g of this was in the form of lipid, and corresponded with enlarged deposits of visible fat.

Vitamin E requirements of the blue tilapia, Oreochromis aureus (Steindachner), in relation to dietary lipid level

Abstract The vitamin E requirement of the blue tilapia, Oreochromis aureus (Steindachner), was evaluated in semipurified diets containing two lipid levels (3% and 6% corn oil) and five levels (0, 10, 20, 40, and 80 mg/kg) of dl-α-tocopheryl acetate. Vitamin E-deficient fish exhibited significantly lower weight gains and feed conversion efficiencies compared to the other fish. In addition, the following vitamin E deficiency signs were observed; skin and fin hemorrhages, anorexia, impaired erythropoiesis, muscle degeneration, ceroid depositions in liver and spleen, and lack of skin color. The vitamin E requirement of the blue tilapia was estimated at 10 mg dl-α-tocopheryl acetate/kg of diet at 3% dietary lipid and at 25 mg/kg of diet at 6% dietary lipid when diets contained 120 mg/kg BHA. It is recommended that vitamin E requirements be expressed as a function of dietary lipid level; 3–4 mg α-tocopheryl acetate per percent corn oil per kg of diet for the blue tilapia.

Dietary Pantothenic Acid Requirement of the Blue Tilapia

Abstract The minimum dietary requirement of the blue tilapia (Tilapia aurea) for pantothenic acid was determined. Five semipurified diets supplemented with 0, 5, 10, 20, or 40 mg calcium D-pantothenate per kilogram of diet were evaluated. Fish fed unsupplemented diets showed significantly poorer (P < 0.05) weight gain, feed conversion efficiency (fish weight gained/dry weight fed), and survival after 12 weeks than fish that received the vitamin. Deficiency signs included exudated gills, fusion of gill filaments and lamellae, and severe fin erosion. Deficient fish recovered completely when fed a diet supplemented with 40 mg calcium D-pantothenate/kg. The minimum pantothenic acid requirement was estimated at 6 mg/kg based on growth. However, based on survival and lack of pathology, a level of 10 mg/kg of diet is recommended.

Vitamin Requirements of Blue Tilapias in a Recirculating Water System

Abstract Fingerling blue tilapias (Tilapia aurea) were offered vitamin-complete semipurified diets supplemented with different levels of either pantothenic acid or choline during three studies. A vitamin-free control diet was included in one study. Fish were kept in aquaria and supplied with recirculated water from a downflow gravel filter. No differences in weight gain, survival, or feed utilization were detected among fish in the different treatments, except for fish fed the vitamin-free diet. Those fish became lethargic and anorexic, lost equilibrium, developed hemorrhagic areas in the skin and fins, and exhibited poor growth and low survival. It is suggested by the results of this study that tilapias could satisfy their requirement for pantothenic acid, choline, and possibly other (but not all) vitamins by feeding on bacteria in a recirculating system.