The aim of this study was to determine the requirement for lysine in the diet of juvenile tambaqui (Colossoma macropomum). In total, 750 juvenile fish (0.34 ± 0.02g) were distributed in tanks arranged in a randomized block design with six treatments, five replications in two blocks, and 25 fish per unit, for 50 d. Six levels of digestible lysine were tested (1.30, 1.48, 1.66, 1.84, 2.02, and 2.20%), in formulated diets based on the ideal protein concept. The performance, feed efficiency, daily deposition of protein and body fat, and nitrogen retention efficiency of the fish were evaluated. The consumption of rations and protein, specific growth rate, body composition, and deposition of body fat were not influenced by the lysine levels tested. The consumption of digestible lysine increased linearly and the efficiency of digestible lysine for weight gain decreased linearly with the increase in lysine levels. The levels of digestible lysine that optimized weight gain and body protein deposition were estimated at 1.73 and 1.78%, respectively. The feed conversion and nitrogen retention efficiency were most improved at 1.66% and 1.84%, respectively. The recommended level of dietary lysine for providing better weight gain and body protein deposition in juvenile tambaqui is 1.78%, equivalent to 2.00% total lysine.
The aim of this study was to determine the requirement of digestible phosphorus in diets for juvenile tambaqui (Colossoma macropomum). 300 juveniles (26.4 ± 0.68 g) were used in a completely randomized design, consisting of six treatments with five replicates and 10 fish per experimental unit. The treatments consisted of six isoprotein, isonitrogenous, and isocalcium rations, with different levels of digestible phosphorus: 0.27; 0.46; 0.67; 0.91; 1.04; and 1.14%. The fish were kept in 30 polyethylene tanks (500 L) with a closed water circulation system and fed six meals per day for 49 days. Parameters of performance and feed efficiency, daily protein, and fat, ash, and phosphorus deposition rates were evaluated. The elevation of digestible phosphorus provided a quadratic increase in feed consumption to a level of 0.92%, linear increase in the consumption of digestible phosphorus, and quadratic reduction in the efficiency of digestible phosphorus for weight gain. The linear response plateau model was the best fit for weight gain and specific growth rate, estimated at 0.55% and 0.56% digestible phosphorus, respectively. The feed conversion and protein efficiency for weight gain improved quadratically up to an estimated level of 0.84% of digestible phosphorus. Body fat deposition improved quadratically up to an estimated level of 0.90% of digestible phosphorus. The linear response plateau model was the best fit for body deposition of protein, ash, and phosphorus, estimated at 0.55%, 0.46%, and 0.59% of digestible phosphorus, respectively. To optimize weight gain, the recommended level of digestible phosphorus in diets for juvenile tambaqui is 0.55%, which corresponds to an estimated level of 0.87% of total phosphorus.
BackgroundLysine is an essential amino acid and, generally, the first limiting in diets for tambaqui (Colossoma macropomum), main native fish produced in continental aquaculture from South America. However, there is a lack of information on their amino acids requirements, especially for maintenance and efficiency of utilization of lysine.ResultsDiets with increasing levels of digestible lysine significantly increased final weight and the weight gain of tambaqui, for all studied ages. Feed intake decreased significantly only for fish weighing 121 g (p < 0.05), and was not affected for other ages. However, digestible lysine consumption significantly increased in all body weights groups evaluated (p < 0.05). In addition, digestible lysine consumption provided sufficient intervals to obtain of values negative, near zero and positive of retention body protein and lysine, allowing estimation of maintenance requirements without extrapolation. The maintenance lysine requirement was determined at the intersection of the point to maintain body protein retention equal to zero, and the efficiency of lysine utilization was the slope of the line between the digestible lysine consumption and its retention, for different tambaqui body weights (121, 235 and 596 g). Linear responses (p < 0.05) were observed between protein retention and body lysine in function on the consumption of digestible lysine for all evaluated body weights, and the parallelism test showed influences of body weight on the values of the maintenance requirement and efficiency of utilization for lysine, with an increase in the maintenance requirement as the fish grow. However, the efficiency of using lysine decreases with the increase in fish body weight.ConclusionsThe requirement of tambaqui for maintenance lysine and efficiency utilization are directly related to the body weight. The requirement for digestible lysine for tambaqui maintenance was 82.03 mg kg-0.7 day-1 for body weights 121 to 235 g and utilization efficiency of 55%. For weight of 596 g, the requirement of maintenance was 106.85 mg kg-0.7 day-1 and 40% of utilization efficiency of lysine.
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