The present study was designed to evaluate the effect of amount of dietary protein levels on blood indicators of protein metabolism and immune condition (blood protein, hemocyanin, osmotic pressure, and hemocytes concentrations), and reproductive capacity of pre-adult Litopenaeus setiferus males (F-0). Assessments were made of the relationship between amount of dietary protein, immune condition, and reproductive condition of the shrimp during the maturation process. Three different diets, with different amounts of protein (DP; 35, 45, and 55%), were evaluated over 55 days and compared with shrimp that were from a baseline group before treatments were administrated. Osmotic pressure, hemocyanin, blood protein, and hemocytes were greater in shrimp from control ponds than those obtained of shrimp fed 35 and 45% DP and similar to that obtained in shrimp fed 55% DP, demonstrating that food in the control pond had a nutritional value to that obtained by feeding amounts of dietary protein beyond 45%. Osmotic pressure, hemocyanin (Hc), blood protein (BP), and hemocytes were influenced by amount of DP with the physiology and immune system of shrimp being influenced by diet. At the same time, a maximum reproductive condition (measured as a proportion of normal cells of the total sperm cells) of shrimp males was observed in shrimp fed 45% DPL with lesser normal cells being present in shrimp fed 35 and 55% DPL. These results indicate that an immune reaction can occur in response to dietary protein with excess DP affecting several physiological functions included the sperm synthesis and sperm quality. Influence on hemocytes concentration in shrimp fed protein in excess could activate an attack on sperm cells in the vas deferens provoking lose of sperm quality in such conditions. Results indicate an optimal DP of 45 for maintaining the broodstock bank of L. setiferus. (c) 2005 Elsevier B.V. All rights reserved.
