IDEAL RELATIONSHIP AMONG DIETARY ESSENTIAL AMINO ACIDS FOR PACU Piaractus mesopotamicus IN THE FINISHING GROWTH PHASE BY THE DELETION METHOD

Deletion method is a technique used for determining the amino acid requirements of fish, which aims to calculate the optimal relationship among essential amino acids (EAAs) in a single experiment. The main advantage of using this method is to avoid the negative effects of factors such as difference in the rearing environments, fish stocks, diets and trial durations, which may affect the performance results.

The present study aimed to determine the ideal relationship among essential amino acids for pacus in the finishing growth phase by the deletion method.

A total of 165 fish with an average initial body weight of 1,109.83±14.26g were distributed in 33 tanks of 1,000L capacity, each being connected to a water recirculation system. The experiment lasted 60 days, consisted 11 treatments with three replicates each, distributed in a completely randomized design. A control diet (CD) was formulated meeting 100% nutritional requirements for the fattening phase of the species under study. The other treatments i.e., EAA limiting diets (LD) were kept isonitrogenous and isoenergetic with a 45% deficiency of each of the 10 EAAs, respectively. The relationship among EAAs was determined by the relationship between body nitrogen retention (N) and the amount of amino acid being deleted from the test diet.

To quantify body N retention, a group of 10 fish was sampled out at the beginning of the experiment and 4 fish from each experimental unit/replicate at the end. Body N content was determined by the Kjedhal method (AOAC, 2000). The values found were used to measure the body N deposition for each treatment during the experimental period using the following equation:

Through the relationship of N deposition levels which were determined for each specified treatment, the ideal EAA ratio was calculated by the following equation:

The optimal balance among EAAs was obtained when the estimated level of each EAA was divided by the estimated lysine level (lysine = 100%).

The data obtained for zootechnical performance and N retention were submitted to One-Way ANOVA and mean contrast analysis by the Dunnett test.

The ideal profile of EAAs obtained for pacu in the finishing growth phase in relation to lysine (100%) was; arginine 41.18%, phenylalanine 31.18%, histidine 14.87%, isoleucine 42.07%, leucine 38,97%, methionine 26.48%, threonine 54.94%, tryptophan 8.58% and valine 45.55%.

Acknowledgments: CNPq (Process No. 130873/2019), FAPESP (Process No. 06343-3/2019, and 25761-4/2013).