Zongjia J. Cheng

Effects of lysine supplementation in plant protein-based diets on the performance of rainbow trout (Oncorhynchus mykiss) and apparent digestibility coefficients of nutrients

Abstract Feeds for carnivorous fish contain large proportions of fish meal. Increasing amounts of plant protein meals must be formulated into fish feeds since fish meal production is not growing worldwide. However, relative to fish meal, many plant protein meals are deficient in lysine. In this experiment, seven diets were made such that the reference diet (Diet 1) contained 32.1% fish meal, 46% crude protein (CP) and 2.25% lysine. The basal diet (Diet 2) had 15% fish meal, 43% CP and 1.5% lysine. Diets 3–7 contained 15% fish meal, 43% CP and 1.65, 1.8, 1.95, 2.1 and 2.25% lysine, respectively. Diets 2–7 were isonitrogenous and all diets were isocaloric. One thousand and fifty rainbow trout (initial body weight 14.9±0.4 g) were randomly assigned to twenty-one 150-l fiberglass tanks with 50 fish per tank, and three tanks per dietary treatment. After an 8-week growth period, weight gains were 82.7, 57.9, 61.7, 73.2, 74.5, 72.8, 71.8 g for fish fed Diets 1–7, respectively. Feed conversion ratios were 0.99, 1.18, 1.18, 1.08, 1.09, 1.07 and 1.08 g feed/g gain for fish fed Diets 1–7, respectively. Results showed that more than 50% fish meal in rainbow trout diets could be replaced by plant protein meals without significantly reducing fish growth and increasing feed conversion ratio if these diets were supplemented with 0.4% or higher levels of lysine. Furthermore, lysine supplementation increased CP and lysine, and reduced fat levels in whole trout body (P 88%) in all diets, ADCs of dry matter were in the range of 72.0–75.6%, and ADCs of phosphorus varied from 47.7% to 61.8%.

Effects of extrusion and expelling processing, and microbial phytase supplementation on apparent digestibility coefficients of nutrients in full-fat soybeans for rainbow trout (Oncorhynchus mykiss)

An experiment was conducted to evaluate the effects of extrusion and expelling processing, and microbial phytase supplementation on apparent digestibility coefficients (ADCs) of dry matter, crude protein (CP), amino acids, and minerals in full-fat soybeans (FFSB) for rainbow trout. Raw, extruded, and expelled soybeans were used. Microbial phytase (Natuphos 5000 l) was added to extruded soybeans at 200, 400, 600, 800, and 1000 FTU/kg diet, and to expelled soybeans at 200 FTU/kg diet. They were each mixed with a casein-gelatin reference diet at a 30:70 ratio to determine their respective ADCs. Nine diets were made and a total of 900 fish (initial mean body weight 170.8±5.5 g) were stocked into 18 150-l tanks with 50 fish per tank. Two tanks were assigned randomly to each diet. Fish were fed their respective diets for 1 week before fecal collection began. Fecal collection by hand-stripping was performed every 3 days for three collections. Yttrium oxide was used as inert marker. Results showed that extrusion processing increased ADCs of CP and sulfur but reduced ADCs of magnesium and total-phosphorus significantly compared to ADCs in raw soybeans (P<0.05). Phytase supplementation in extruded soybeans increased ADCs of magnesium, total-phosphorus, phytate-phosphorus, manganese, and zinc significantly (P<0.05). Phytase supplementation in expelled soybeans increased ADCs of CP, sulfur, total-phosphorus, and phytate-phosphorus significantly compared to ADCs in raw soybeans (P<0.05). The optimum dosage of phytase used to effectively releasing phosphorus and other minerals in extruded full-fat soybeans is approximately 400 FTU/kg diet for rainbow trout.

Nutritional Value of Diets Containing Distiller's Dried Grain with Solubles for Rainbow Trout, Oncorhynchus mykiss

Abstract A feeding trial using corn distillers dried grain with solubles (DDGS) was conducted to evaluate the nutritional value of DDGS and effects of lysine and methionine supplementation in DDGS-based diets on the performance of rainbow trout, Oncorhynchus mykiss. The DDGS-based diets were made such that DDGS was used at 7.5% (diet 2), 15% (diet 3), and 22.5% (diet 4) inclusion levels without supplementing crystalline L-lysine-HCl and DL-methionine, and was used at 7.5% (diet 5), 15% (diet 6), and 22.5% (diet 7) with lysine and methionine supplementation in a 2 × 3 factorial design. A fish meal-based diet (diet 1) was used as a control. The control and lysine and methionine supplemented diets contained 2.2% lysine and 1.1% methionine. A total of 630 fish (initial body weight 49.8 g) were randomly stocked into twenty-one, 150-L tanks with 30 fish/tank and 3 tanks/diet. Fish were fed to apparent satiation 3 times/day and 6 days/week. After a 6-week growth period, weight gain (WG) offish fed diets 1 to 7 was: 48.9, 43.9, 46.5, 42.9, 51.3, 54.3, and 46.4 g, respectively. Feed conversion ratio (FCR) offish fed diets 1 to 7 was: 1.21, 1.35, 1.25, 1.34, 1.20, 1.11, and 1.29 g diet/g gain, respectively. Survival was 100% for fish fed all diets. Two-way ANOVA showed that lysine and methionine supplementation improved WG (P = 0.0002) and FCR (P = 0.0011). Fish fed diets containing 15% DDGS, or replacing 50% offish meal on isonitrogenous and isocaloric basis, were not significantly different from fish fed the fish meal-based diet in terms of WG, FCR, and survival (P > 0.05), indicating that DDGS could be used at the 15% inclusion level, or replace up to 50% offish meal. Furthermore, DDGS could be used at the 22.5% inclusion level, or replace up to 75% of fish meal in rainbow trout diets with lysine and methionine supplementation.

Apparent digestibility coefficients and nutritional value of cottonseed meal for rainbow trout (Oncorhynchus mykiss)

Abstract Cottonseed meals (CSM) from four different locations in the southern US were evaluated to measure apparent digestibility coefficients (ADC) of nutrients using yttrium as an inert marker. One type of CSM was used at 0% (diet 0), 5% (diet 5), 10% (diet 10), 15% (diet 15), and 20% (diet 20) inclusion rates in experimental diets (44% crude protein, 22% crude fat) to evaluate its nutritional value. A total of 450 rainbow trout (initial mean body weight 11.2±0.4 g) were randomly stocked into fifteen 150-l fiberglass tanks with 30 fish per tank and 3 tanks per diet. Fish were fed to apparent satiation 3 times a day and 7 days per week. The ADC of the four CSM groups were: dry matter, 50.8–75.5%; fat, 60.2–78.6%; crude protein, 81.6–87.9%; potassium, 98.9–99.6%; magnesium, 45.1–60.5%; sodium, 89.1–92.7%; phosphorus, 53.3–56.2%; copper, 53.3–65.6%; iron, 34.0–60.4%; manganese, 15.1–31.6%; zinc, 6.1–33.4%; essential amino acids, 80.2–96.1%; and non-essential amino acids, 62.5–94.3%. After a 6-week growth period, average weight gain of fish fed diets 0 to 20 was: 42.4, 39.1, 39.4, 34.2, and 31.8 g, respectively. Average feed conversion ratio of fish fed diets 0 to 20 was: 0.94, 0.99, 1.01, 1.12, and 1.13, respectively. Survival was >98% for fish fed all diets. Results showed that the ADC of most nutrients in CSM obtained from different locations were different. Fish fed CSM diets at the 5% or 10% inclusion rates were not significantly different compared to fish fed the fish meal control diet in terms of weight gain, feed conversion ratio, and survival ( P >0.05), indicating that CSM could be used at the 10% inclusion rate in rainbow trout feed formulations.

Plant protein ingredients with lysine supplementation reduce dietary protein level in rainbow trout (Oncorhynchus mykiss) diets, and reduce ammonia nitrogen and soluble phosphorus excretion

Abstract Two experiments were conducted to evaluate the effects of lysine supplementation on the reduction of dietary crude protein (CP), and reductions of total ammonia nitrogen (TAN) and soluble phosphorus (soluble-P) discharged into water by rainbow trout. In Experiment 1, eight diets were prepared, such that Diet 1 contained 32.8% fish meal, 42% CP and 2.1% lysine. Diet 2 had the same amount of fish meal and lysine as in Diet 1, but only 37% CP. Diets 3–8 contained 16.4% fish meal, 37% CP, and 1.5%, 1.65%, 1.8%, 1.95%, 2.1%, and 2.25% lysine, respectively. Rainbow trout (initial body weight: 26.9±0.2 g) were randomly assigned to triplicate tanks per diet with 50 fish per tank. After an 8-week feeding trial, weight gains were 112.5, 111.8, 87.5, 94.4, 103.0, 105.7, 101.8, and 102.6 g; feed conversion ratios were 0.99, 1.01, 1.16, 1.15, 1.10, 1.08, 1.10, and 1.09 g feed/g gain for fish fed diets 1–8, respectively. Survival was greater than 99% for all treatments. In Experiment 2, 130 fish (102.4±8.3 g) per tank were moved to flowing water tanks (140 l) and fed the same diets as in Experiment 1 for 1 week, and then TAN and soluble-P in the wastewater were measured for 2 consecutive days. The values of TAN discharged by the fish 8 h after feeding were 9.69, 8.56, 8.44, 7.81, 7.19, 6.65, 6.24, and 6.29 mg/l, and discharged soluble-P were 1.01, 0.85, 0.45, 0.31, 0.30, 0.26, 0.25, and 0.14 mg/l for fish fed Diets 1–8, respectively. Results showed that lysine supplementation in plant protein-based diets allowed dietary CP to be reduced without reducing fish performance. TAN and soluble-P excretions by rainbow trout were reduced in plant protein-based diets (37% CP) with lysine supplementation compared to the control fish fed with fish meal diets with either 42% or 37% CP.

Effects of Microbial Phytase Supplementation in Corn Distiller's Dried Grain with Solubles on Nutrient Digestibility and Growth Performance of Rainbow Trout, Oncorhynchus mykiss

Abstract Two experiments were conducted to evaluate the effects of microbial phytase in corn distillers dried grain with solubles (DDGS) on apparent digestibility coefficients (ADCs) and growth performance of rainbow trout, Oncorhynchus mykiss. In experiment 1, DDGS was supplemented with phytase at 0,300,600,900, and 1200 FTU/kg diet. A total of 180 fish (129.1±9.3 g) were stocked into six 140-L tanks with 30 fish/tank. Fish were assigned randomly to a reference diet and each of the 5 diets containing DDGS. Yttrium oxide was used as an inert marker. Results showed that ADCs in DDGS supplemented with different dosages of phytase were: dry matter, 49.1-58.6%; crude fat, 78.9-88.9%; crude protein, 80.0-91.9%; gross energy, 50.5-66.6%; minerals, -7.3-99.7%; and amino acids: 73.9 to 96.8%. In experiment 2, abasal diet containing 15% DDGS supplemented with lysine and methionine was used to determine if trace mineral supplemental levels in rainbow trout diets could be reduced if microbial phytase was supplemented. Six diets were made with trace mineral premix supplementation at 0.1, 0.08, 0.06, 0.04, 0.02, and 0%. Phytase was not supplemented in the basal diet, but supplemented at 500 FTU/kg diet in all other diets. Ten-week results showed that there were no significant differences in fish weight gain, feed conversion ratio, and survival (P < 0.05). There were no significant differences in fish body composition and apparent nutrient retention among fish fed all diets, except that fish fed a diet without trace mineral supplementation had the lowest zinc level and the highest manganese retention. Results indicated that phytase was effective in releasing most of minerals, and that trace mineral supplementation level could be reduced when phytase was used in rainbow trout diets.

Effects of Extrusion on Nutritional Value of Diets Containing Corn Gluten Meal and Corn Distiller's Dried Grain for Rainbow Trout, Oncorhynchus mykiss

Abstract The effects of diet processing methods on diets containing increasing levels of a combination of corn distillers dried grain with solubles (CDDGS) and corn gluten meal (CGM) to replace fish meal in diets of rainbow trout were investigated. A two by four factorial treatment arrangement was used with two types of diet processing methods (cold-pelleted and extruded) and four levels of corn products replacing fish meal protein (0, 25, 50, or 75%). There was an effect of processing method and level of corn products on weight gain and feed conversion ratio, and an interaction of those effects. Extrusion of diets containing the corn products did not improve fish growth compared to fish fed the cold-pelleted feed (extrusion of the wheat-containing diet did improve weight gain and feed conversion). There were interactions between process type and level of corn products on protein retention efficiency, and apparent digestibility coefficients for both dry matter and energy. The presence of indigestible carbohydrate in the CDDGS limited replacement of fish meal with the corn products to 18% of the protein.