Protein requirements of juvenile pampo, Trachinotus marginatus, and possible substitutes for fish meal
This thesis aimed to estimate the needs for essential amino acids, the influence of different levels of protein on the performance of juveniles of Trachinotus marginatus, as well as the feasibility of replacing fish meal with soy protein concentrate for juveniles of this species. All the fish used in this thesis were collected by means of trawl in the surf zone of Cassino beach, Rio Grande - RS, and transported to the Estuarine and Marine Pisciculture Laboratory of the Federal University of Rio Grande - FURG. At this place the fish were subjected to prophylactic baths with 50 ppm formalin for one hour and remained for three days acclimation on for four days. To estimate the needs for essential amino acids, carcass and muscle samples were collected.After analyzing the amino acid composition of the samples, the requirements for essential amino acids were estimated, based on the index A / E [(individual SEA / total SEA) * 1000] determined for each sample. Pampus juveniles have a composition and demand for amino acids very similar to other marine teleosts. As long as the requirements for essential amino acids are not determined experimentally, the requirements estimated in this experiment can be used to formulate balanced diets for T. marginatus. To evaluate the protein level capable of producing the best growth of juvenile pampo, groups of ten (10) fish were stored in nine 50 L tanks in a water recirculation system composed of a mechanical filter, biological filter and ultra violet filter.The fish were fed until apparent satiety four times a day for 60 days with diets containing 43, 54 or 64% crude protein (PB43, PB54 and PB64). The experimental design was completely randomized and in triplicate. Weight gain, specific growth rate and feed conversion did not differ significantly. However, the addition of protein consumed increased the hepatosomatic index and the excretion rate of postprandial ammonia, as well as reduced protein efficiency. Fish fed the PB43 diet showed lower concentrations of hepatic oxalacetic glutamic transaminase in addition to lower concentrations of triglycerides in muscle and liver. Carcass composition, glycogen and total protein content for muscle and liver did not show significant differences,except for the highest lipid content of the carcass in the PB43 treatment. These results suggest that the best use of protein by juvenile pampo occurred when they consumed the 43% protein diet, without prejudice to growth. The feasibility of replacing fish meal with soy protein concentrate was investigated by feeding young pampo juveniles with diets containing 0, 25, 50, 75 or 100% soy protein concentrate to replace fish meal (CPS0, CPS25, CPS50, CPS75 and CPS100, respectively). The diets were formulated to contain 43% crude protein. 16 juvenile pampo juveniles were stored in each of the 15 300 L tanks that comprised five water recirculation systems equipped with mechanical filter and biological filter.The fish was fed four times a day until apparent satiety for 45 days. Feed conversion, protein efficiency rate, lipid efficiency rate and lipid retention did not differ (p> 0.05). Final average weight, weight gain, specific growth rate, and hepatosomatic and viscerosomatic indices were lower for treatment CPS100 (p <0.05), but were not changed until treatment CPS75. The total food and protein consumption of animals fed the CPS100 diet was lower than the other treatments, which caused less protein retention in fish. The results indicate that fishmeal can be substituted by CPS in up to 75% in the diets for Trachinotus marginatus without causing a loss in fish performance.The data obtained in this thesis allow the formulation of diets that meet the requirements of essential amino acids, with adequate protein content and with the possibility of replacing up to 75% of fish meal with soy protein concentrate.