Coeficientes de digestibilidade aparente da proteína e de aminoácidos de ingredientes de origem animal e vegetal utilizados em dietas para o camarão Litopenaeus vannamei

Abstract

The determination of digestibility is essential to meet the nutrient requirements of farmed animals, formulate on a least-cost basis and minimize excretion of nutrients in water. This study aimed at determining the apparent digestibility coefficients (ADC) for crude protein (CP) and essential amino acids (EAA) of 12 ingredients commonly used in the composition of shrimp feeds for the rearing of juvenile Litopenaeus vannamei. The following plant-derived feedstuffs, in addition to rendered animal by-products of terrestrial and aquatic origin were evaluated: soy protein concentrate (SPC), corn gluten meal (CGM), soybean meal (SBM), wheat flour (WHF), poultry and feather by-product meal (PBM), meat and bone meal (MBM), feather meal (FEA), blood meal (BLD), tilapia waste meal (TLM), Brazilian marine fish processing waste meal (FBM), salmon by-product meal (SLM) and krill meal (KLM). The ADC was estimated by the indirect method using an inert marker, chromium III oxide (Cr2O3), at 10 g/kg (as is basis) in a reference (REF) mixture. Each raw material was incorporated into the REF mixture at a 30-70 ratio. The study was conducted over three experimental stages, lasting 29-30 days each. Sampling of shrimp feces took place by syphoning. Shrimp of 6 and 8 g were stocked in 44 tanks of 61 L each. A total of 11 tanks were assigned to each test ingredient, four for the REF diet. At harvest, final shrimp survival exceeded 96%. Final shrimp body weight exhibited a significant linear correlation with dietary CP and EAA. In the case of CP, lysine and methionine, higher dietary levels of these nutrients resulted in increased shrimp body weights. ADC ranged from 66.7% for a diet containing BLD to 84.2% for the REF diet. Higher ADC were observed for aquatic proteins compared to plant and land animal proteins. Aside from SPC (ADC = 79.3%), other plant ingredients, SBM, CGM and WHF, showed a low ADC of protein, between 32.0 to 47.7%. Among land-animal by-products, ADC of protein was higher in MBM, PBM, BLD, and FEA (71.2, 62.8, 48.6 and 45.9%, respectively). With the exception of KLM (61.6%), ADCs of protein for all other aquatic ingredients exceeded 80%. It can be concluded that TLM, FBM, and SLM, resulted in a better utilization of protein and EAA by L. vannamei, while KLM promoted the highest growth performance.