Exigências de lisina para mantença de tambaqui

Abstract

Lysine is one of the essential limiting amino acids in ingredients used in formulations of diets for tropical fish and is used almost exclusively for protein synthesis. Currently, the requirement for digestible lysine for fish is obtained through empirical studies (dose response), neglecting the requirement of maintenance. The requirement for lysine for maintenance may be defined as an amount of lysine ingested for its equilibrium in body nitrogen or lysine, there being no anabolism or catabolism of body protein or lysine. Tambaqui (Colossoma macropomum) stands out as the main native species marketed in the country, but information on its amino acid requirements for maintenance and production is still scarce in the literature. The objective of this study was to determine the digestible lysine requirement for the maintenance of tambaquis in the growth stages (121.23 to 145.75 g) and fattening (595.93 to 652.4 g) using increasing levels of digestible lysine in the diet. The initial mean weight was 121.23±1.23 g in the first phase and in the second phase with initial weight of 595.93±47.57 g. Both experiments were completed in a completely randomized design (DIC) for a set of five replicates. The treatments consisted of diets containing 0.219; 0.438; 0.657; and 0.876% digestible lysine, formulated by the dilution technique. To determine the requirement for digestible lysine for maintenance, the amount of digestible lysine ingested (mg/kg0,7 /day) capable of providing a nitrogen retention (NR) equal to zero obtained by comparative slaughter was considered. The data were compared with regression (P <0.05) with the use of digestible lysine (mg/kg0,7/day) as a dependent variable and nitrogen retention (mg/kg0,7 /day) as a dependent variable. The requirements of digestible lysine for tambaqui maintenance were estimated in the growth and fattening phases of 73.39 and 114.07 mg/kg0,7 /day, respectively. By means of the inverse slope values, it was possible to obtain the digestible lysine consumption for the growth and fattening phases 17 and 20 mg, respectively, for the deposition of 1 g of protein. The determination of the digestible lysine requirement for tambaqui maintenance is a starting point for the elaboration of prediction equations for the total digestible lysine requirement for any production phase. In addition, it will allow the industry to elaborate rations with lysine levels suitable for tambaqui, providing less excretion of nitrogenous compounds to the aquatic environment and the balance between maximum productivity and cost of production.