Reports from hatcheries have demonstrated that commercially available diets are inadequate for June Suckers Chasmistes liorus and suggest that fish quality can be improved through species‐specific diet optimization. To determine dietary protein and lipid levels for juvenile June Suckers, practical‐type diets were formulated with 35, 40, or 45% protein and 8, 12, or 16% lipid and tested in a 3 × 3 factorial design. Two additional diets (45% protein and 16% lipid [45:16] without dicalcium phosphate supplementation and 45:16 with 2× dicalcium phosphate) were formulated to test the necessity of dicalcium phosphate supplementation. Each diet was fed to three replicate tanks (average initial fish weight ± SD = 4.48 ± 0.24 g) of fish per treatment (85 fish/tank); only duplicate tanks were used for the nondicalcium phosphate‐supplemented treatment. Fish were reared in 80‐L tanks supplied with 4 L/min of 22°C spring water and fed 6–4% body weight (BW)/d by automated belt feeders, 6 d/week. At the end of 12 weeks of culture, tissue samples were obtained to determine nutrient partitioning. An acute temperature challenge was also conducted to investigate dietary adequacy. Significant effects of diet on growth and temperature tolerance were observed. Fish fed the diet with 45% crude protein gained more weight than did fish fed 40% or 35% crude protein, and fish fed 16% dietary lipid gained more weight than did fish fed 12% and 8% crude lipid. However, the composition of this growth indicated that fish fed the 16% lipid stored larger amounts of lipid in both the visceral cavity and the muscle. A significant negative interactive effect of dietary protein and lipid on temperature tolerance was observed at 45% crude protein and 16% lipid. Results of this study define acceptable ranges of dietary protein and lipid for juvenile June Suckers and provide culturists information to make better choices regarding appropriate diets for this species.
Tilapia is the second most consumed farmed fish after carp and the most widely grown farmed fish. However, significant price increases in ingredients in recent years threaten profitability of the industry because dietary costs are approximately 60% of production costs. Therefore, the objective of this study was to optimize dietary protein and lipid levels of juvenile tilapia cultured in high-intensity recirculating-water system and assess dietary effects on stress tolerance. To achieve this objective, a factorial treatment design with diets formulated to contain three levels of dietary protein (28, 32, and 36%) and three levels of dietary lipid (3, 6, and 9%) was employed. Juvenile tilapia (34.5 ± 0.4 g initial weight) were randomly assigned to each of 24 tanks and fed one of the nine diets, three feedings per day to apparent satiation, 6 d/wk for 12 wk. Fish were weighed and counted every 3 wk and feed consumed recorded weekly. Tilapia weight gain, feed conversion, feed intake, and proximate composition were significantly affected by diet. Following the feeding trial, tilapia were subjected to a 24 h simulated live haul where fish were stocked into a static water system at 0.24 kg/L of water. Glucose, lactate, and cortisol measurements were taken at time 0, 24, and 72 h after fish were placed into hauling containers. There was significant effects (P < 0.05) of crude lipid and crude protein on blood chemistry parameters. These data indicate that practical diet formulations can be improved to enhance growth rates, production of tilapia, and stress response during live hauls.
Distillers dried grains (DDG) with solubles (DDGS) is a product that has shown potential as a protein source for some fish species, but high inclusion rates of DDGS have not always been successfully achieved for Rainbow Trout Oncorhynchus mykiss. Our objective was to determine whether inclusion of a mycotoxin deactivation product (Biofix Plus) could improve the ability of high‐protein DDG (HPDDG) to replace a portion of the fish meal in diets for Rainbow Trout. The 2 × 2 factorial feeding trial examined protein source (menhaden fish meal [MFM] or HPDDG) with or without Biofix Plus. A control diet (42% digestible protein, 20% crude lipid, 25% MFM) was compared to a test diet in which HPDDG replaced 12% of the total MFM on a digestible‐protein basis (24% HPDDG inclusion). Diets were fed to juvenile Rainbow Trout (initial weight: mean ± SE = 30.5 ± 1.6 g) in four replicate tanks per treatment for 9 weeks in a 15°C recirculating system. At the conclusion of the feeding trial, we observed no negative effects of fish meal replacement on growth or feed conversion ratio; no benefit of Biofix Plus supplementation was observed. These data indicate that when Rainbow Trout diets containing a high‐quality DDGS product are balanced for digestible protein, lysine, methionine, and threonine, dietary fish meal levels can be successfully reduced to 13% without compromising growth and without the need for mycotoxin deactivator inclusion.
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