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-The objective of this work was to evaluate the performance of Litopenaeus vannamei fed different levels (0, 25, 50, 75, and 100%) of soybean protein concentrate (63.07% crude protein, CP) to replace fish meal-by product (61.24% CP). The study was conducted in clear water in fifteen 800 L tanks equipped with aeration systems, constant heating (29 ºC), and daily water exchange (30%). Each tank was stocked with 37.5 shrimp/m 3 (3.03±0.14 g). Feed was supplied four times a day, at 6% of the initial biomass, adjusted daily. After 42 days, the weight gain of shrimp fed diets with 0 and 25% protein replacement was higher than that observed in shrimp fed 100% replacement, and there were no differences among those fed the other diets. Feed efficiency and survival did not differ among shrimp fed different protein replacements. There was a negative linear trend for growth parameters and feed intake as protein replacement with soybean protein concentrate increased. Fish meal by-product can be replaced by up to 75% of soybean protein concentrate, with no harm to the growth of Pacific white shrimp.

This study evaluated the performance, immunology, and survival of the Pacific white shrimp Litopenaeus vannamei to experimental challenge to Vibrio alginolyticus based on the use of the probiotic Lactobacillus plantarum and the combined use of probiotic and butyrate. Four different diets resulted from the addition of additives: butyrate, probiotic, butyrate + probiotic, and control (no additives). The attractiveness of the diets was assessed by the percentage of positive choices and rejections, using a dual-choice Y-maze format aquarium. The shrimps were fed during four weeks and performance parameters, intestinal microbiota, and immunological parameters were all evaluated. Subsequently, the shrimps were challenged with V. alginolyticus and after 48 h, survival and immunological parameters were evaluated. The results showed increased attractiveness and intake, but only with diets supplemented with sodium butyrate. However, other diets were not rejected. No difference in performance or immunological parameters was observed among the different diets. Also, among the treatments, no difference in Vibrio spp., or total heterotrophic bacteria counts, was found in the intestinal tract. However, the lactic acid bacteria count was higher in the intestinal tract of shrimps fed diets supplemented with probiotic. After bacterial challenge, shrimp fed all diets had a greater survival when compared with the control group. Lactobacillus plantarum and sodium butyrate increase the resistance of shrimp to infection with V. alginolyticus, but do so without affecting performance, immunological parameters, or Vibrio spp., and total heterotrophic bacteria counts in the intestinal tract.

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