Salts of organic acids selection by multiple characteristics for marine shrimp nutrition

Organic acids or their salts can be used as growth promoters in aquaculture, aiding in pathogen inhibition in the intestinal tract, providing energy to aquatic organisms, and improving the digestibility of dietary nutrients, such as nitrogen and phosphorus. The objective of the present study was to select salts of organic acid such as sodium acetate, sodium butyrate, sodium citrate, sodium formate, sodium lactate and sodium propionate, with potential to be used as feed additives for marine shrimp. One performed and analyzed in vitro inhibition of three Vibrio species (Vibrio harveyi, V. alginolyticus, and V. anguillarum), at two different pH values (6.2 and 7.1). The attractiveness of the diets was assessed by the percentage of positive choices and rejection, in aquariums, of dual choice Y-maze format. The leaching of different salts in the diets was also evaluated after immersion in seawater for 0, 15, 30, 45 and 60 min. In order to evaluate the intestinal bacterial count alteration, shrimps were fed, during 14 days, with diets containing 2% of their salts plus a control diet. Later, it was possible to determine the bacteriological count of total heterotrophic marine bacteria (Marine Agar) vibrio species (TCBS Agar) and bacteria lactic acid (MRS Agar). Subsequently, data of bacterial inhibition in vitro and in vivo, besides the tests of attractiveness and leaching of diets were used to select the best salts by the ideotype test through Mahalanobis distance. After, the top three salts were used in the tests of feed intake and digestibility of dry matter, protein, energy and phosphorus. The results of this study clearly indicate that salts of organic acids possess inhibitory activity against pathogenic vibrio species in marine shrimp, with propionate, butyrate, and acetate salts exhibiting the highest inhibitory capacity (p<0.0001). Regarding the stability of salts in the diets, molecules with a higher carbon number (C), such as butyrate (4C), lactate (3C), and citrate (6C), showed less leaching. There was also increased attractiveness and consumption of commercial diets when they were supplemented with sodium propionate and butyrate (p<0.05). Furthermore, sodium propionate decreased the vibrio species concentration in the intestinal microbiota of marine shrimp (p<0.05), Litopenaeus vannamei, besides increasing the apparent digestibility of energy (p<0.01) and phosphorus (p<0.02). Thus, we conclude that the use of salts of organic acids could improve marine shrimp nutrition and health and that the salt propionate has the greatest potential for use as a diet supplement for L. vannamei. (C) 2012 Elsevier B.V. All rights reserved.