Search Results (4)

Vitamin A (VA) is an essential micronutrient that improves growth, immune activity, and antioxidant responses in fish. This study focuses on optimizing VA dietary levels for Oncorhynchus kisutch (Coho salmon) alevins. A 12-week trial was conducted using seven diets containing graded dietary VA levels of 244, 957, 1902, 3494, 6906, 10,248, and 25,213 IU/kg. A total of 2100 fish were reared in 21 tanks; 100 fish were housed in each tank, and 3 tanks represented one treatment. Peak (SGR) and FBW were observed at 6906 IU/kg. Excess VA levels (>15,000 IU/kg) compromised feed conversion efficacy and led to oxidative stress. Analysis of proximate composition resulted in protein and lipid deposition at optimal VA levels. However, excess may have led to metabolic disturbances and reduced ash content. The activity of the antioxidant enzymes catalase (CA), acid phosphatase (ACP), alkaline phosphatase (AKP), and total superoxide dismutase (T-SOD) revealed biphasic patterns, peaking at 6906 IU/kg and dropping when VA levels were exceeded, inducing pro-oxidant effects. Malondialdehyde (MDA), the indicator of toxicity, had a minimal value of 15,000 IU/kg. VA accumulation in the liver showed a dose-dependent relationship, while excess storage (>25,000 IU/kg) induced hepatotoxicity. Quadratic regression was used to identify the optimum VA levels required in Coho salmon alevins, ranging from 6906 to 10,248 IU/kg. Polynomial quadratic regression results indicated that the predicted dietary inclusion of VA at 3000 IU/kg and 15,000 IU/kg may yield better results of T-SOD and MDA. Real-world experimentation is recommended to explore long-term VA optimization with other nutrients and promote better feed utilization and sustainable aquaculture practices. Full article

Vitamin K₃ (VK₃) is an essential micronutrient for fish growth and metabolism. To determine the optimal required dietary concentration of VK, a 12-week-long trial was planned to investigate the impact of VK₃ on growth performance, muscle composition, liver menaquinone-4 (MK-4), whole-body MK-4 concentration, and antioxidant capacity (T-AOC) in coho salmon alevins. A total of 2100 coho salmon alevins were divided into twenty-one tanks, with 100 alevins in each tank, and three tanks represented one group. Each of the seven groups were randomly assigned to one of the experimental diets formulated with varying levels of menadione nicotinamide bisulphite (VK₃), i.e., 0.16 (control), 5.25, 10.22, 14.93, 20.51, 40.09, and 59.87 mg/kg, respectively. The results revealed that the inclusion of VK₃ from 5.25 to 40.09 mg/kg improved (p < 0.05) the survival rate (SR), weight gain (WG), specific growth rate (SGR), and feed conversion ratio (FCR), while no effect (p > 0.05) was observed on the hepatosomatic index (HSI), viscerosomatic index (VSI), Fulton’s condition factor (K), and muscle composition. The whole-body MK-4, liver MK-4, liver T-AOC, total superoxide dismutase (T-SOD), and catalase (CAT) enzymes were also increased (p < 0.05). Malondialdehyde (MDA) contents were reduced (p < 0.05) in all supplemented groups with a decreasing trend. The predicted optimal required dietary concentrations of VK₃ were found to be 34.0, 43.5, 38.54, and 31.97 mg/kg based on WG, SGR, liver MK-4 concentration, and T-AOC, respectively, by quadratic regression analysis. It is concluded that the dietary VK₃ has improved the growth performance and antioxidant status in alevins during early development in the range of 31.97 to 43.5 mg/kg diet. Full article

The suitable dietary L-lysine concentration for coho salmon (Oncorhynchus kisutch) alevins was assessed by a dose response feeding trial. Six experimental diets were made with graded L-lysine concentrations of 2.29%, 2.81%, 3.32%, 3.80%, 4.27%, and 4.78% of the dry matter, respectively, each of which was fed to triplicate groups of 100 alevins (initial body weight: 0.30 ± 0.01 g) in 18 plastic baskets (water volume 240 L). The alevins were cultured in a flowing freshwater system and fed manually to apparent satiation four times a day for 12 weeks. The survival rate of alevins did not differ significantly among the dietary groups. The specific growth rate (SGR), protein efficiency ratio (PER), and body protein deposition (BPD) increased significantly (p < 0.05) with the increase in dietary lysine concentration up to 3.80% and then reduced as lysine level further increased. The feed conversion ratio (FCR) had an inverse trend to SGR. The whole-body crude protein content of the alevins increased significantly with increasing dietary lysine level, while crude lipid content showed the opposite trend. In comparison, the contents of morphological indices, whole-body moisture, and ash were not affected significantly (p > 0.05) by the different dietary lysine concentrations. The highest contents of lysine, arginine, and total essential amino acids (EAAs) were observed in the group with 4.27% dietary lysine concentration, which did not differ significantly from those in the 3.32%, 3.80%, and 4.78% groups but was significantly higher than those in the 2.29% and 2.81% groups. Similarly, valine had the highest content in the group with 4.78%. The variations in dietary lysine had no significant impacts on other EAA and non-EAA contents except glycine, which increased with increasing dietary lysine level. Second-order polynomial model analyses based on SGR, PER, BPD, and FCR evaluated the optimum L-lysine requirements of coho salmon alevins as 3.74%, 3.73%, 3.91%, and 3.77% of the diet or 6.80%, 6.78%, 7.11%, and 6.85% of dietary proteins, respectively. Full article

A 12-week feeding trial aimed to evaluate the effects of dietary linoleic acid (LA, 18:2n-6) on the growth performance, fatty acid profile, and lipid metabolism enzyme activities of coho salmon (Oncorhynchus kisutch) alevins. Six experimental diets (47% crude protein and 15% crude lipid) were formulated to contain graded LA levels of 0.11%, 0.74%, 1.37%, 2.00%, 2.63%, and 3.26%. Each diet was fed to triplicate groups of 50 alevins with an initial body weight of 0.364 ± 0.002 g, which were randomly assigned to 18 white plastic tanks (0.8 × 0.6 × 0.6 m, 240 L/tank). Fish were reared in a freshwater flow-through rearing system and fed to apparent satiation four times daily. The survival rate was not significantly different among the treatments (p > 0.05). However, the 1.37% LA group significantly improved the final body weight and specific growth rate (SGR) (p < 0.05) of alevins. The feed conversion ratio (FCR) in the 1.37% LA group was significantly lower than those in other groups (p < 0.05). The whole-body lipid content significantly decreased (p < 0.05) with dietary LA levels increasing from 0.74% to 2.00%. The fatty acid composition of the total lipid in muscle was closely correlated with those in the diets. The dietary LA level of 1.37% led to significantly higher activities of liver lipoprotein lipase (LPL) and hepatic lipase (HL) than those of other groups (p < 0.05). Hepatic malate dehydrogenase (MDH) and fatty acid synthase (FAS) decreased with the increase in the dietary LA levels from 0.11% to 1.37%. The lowest MDH and FAS activities were obtained in the 1.37% LA group (p < 0.05). This study indicated that an appropriate amount of dietary LA was beneficial for the growth and lipid metabolism of coho salmon alevins, and the results of the quadratic regression analysis of the SGR and FCR indicated that the optimal dietary LA requirements were 1.25% and 1.23% for coho salmon alevins, respectively. Full article