Valor nutricional de flocos microbianos e rações vegetais para o desempenho zootécnico do camarão branco, litopenaeus vannamei

Abstract

The aquaculture industry is looking for alternatives to minimize production costs and the impact of wastewater discharge through the replacement of fishmeal by microbial flocs, vegetable ingredients and the effect of feed rate on the performance of juvenile white shrimp, Litopenaeus vannamei, farmed without exchange of water in the presence of microbial flakes. The aim of this study was to evaluate the nutritional value of microbial flocs and vegetable ingredients in the diet of the shrimp Litopenaeus vannamei. The first phase compared the bioavailability of crude protein and fat from meals with microbial flocs, using shrimp farming water and clean sea water. It was observed that microbial flocs meals contained high content of ash (from 649.2 to 591.0 g / kg) and low crude protein (95.9 - 137,3g / kg). The final survival of shrimp was 93.2 ± 0.8% and the biomass gain of 37.1 ± 1.8 g / tank. The final body weight of shrimp ranged from 9.01 ± 0.15 to 9.45 ± 0.13 g. The microbial flocs produced with waste water from shrimp farming or clean sea water through sequence reactors had low protein content available for juvenile L. vannamei. Despite the low levels of fat were present, they have proven to be highly available for the species. The inclusion of microbial flake meal in the diet seemed to have a growth promoting effect which may be associated with trace minerals or other nutrients. The second phase assessed the effects of the soy protein rate, lipid content and minimum level of krill in meals based on vegetable ingredients on the growth performance and digestibility of L. vannamei. The diets based on plants ranged in soybean meal (SBM) and soy protein concentrate (SPC) and in lipid content in the diet. A salmon by-product meal diet was used as control. The krill meal was included in a new group of diets based on plant ingredients. In clean water tanks, no effect on the SBM:SPC rate and lipid content was detected in the survival of shrimp. However lipid levels in the diet of 80 and 121 g / kg combined with a high SPC SBM resulted in lower final body weight and poorer digestibility of crude protein, respectively. The inclusion of krill meal in vegetable diets improved the feeding only 10 g / kg of diet, while 20 g / kg accelerated the shrimp growth, increased the yield and reduced FCR. The third phase evaluated the growth performance of the white shrimp L. vannamei farmed in a heterotrophic system. The work was carried out in two steps: (1) rainy season and (2) dry season. Shrimps weighing 3.69 ± 0.68 g (n = 240) and 2.13 ± 0.51 g (n = 300) were submmited to progressive increasing in meal of 40%, 54%, 81%, 84 % and 113% and 52%, 77%, 98%, 127% and 153% in steps 1 and 2, respectively. In the culture, the water quality parameters were measured. In this two-step farming, the shrimps were fed with a diet containing 235g / kg of crude protein and molasses. The survival, yield, final body weight, weekly growth and feed conversion factor (FCR) were obtained at harvesting. There was an increase in sedimentary and total solids with the increasing of the feeding rate in the treatments, including the control tanks, suggesting that microbial flakes may have contributed to the better performance of the animals. In both steps of farming, there was a significant increase in the final body weight gain (9.84 ± 1.79 and 10.45 ± 1.55g) and in the growth (0.70 ± 0.01 and 0.82 ± 0.05g), from the gradual increasing of the feed. The FCR increased, however, no statistical difference was observed between the treatments in the rainy season, however, in the dry season, there was statistical difference between treatments of 153% and 52% and with the control. The evaluation of the effect of feed rate on the performance of juvenile of L. vannamei farmed in heterotrophic system and fed with gradual increasing of feed, showed have improved the growth performance of the animals.