Evaluation of a high protein distiller's dried grains product as a protein source in practical diets for Pacific white shrimp Litopenaeus vannamei

Abstract

A series of trials were conducted to evaluate the efficacy of a high protein distiller's dried grains (HPDDG) product in practical shrimp feed formulation. In the three growth trials, the basal diet (35% crude protein, 8% lipid) consisted primarily of fish meal (FM), soybean meal (SBM), whole wheat, and corn starch. In trial 1 and trial 2, test diets were produced by supplementing the basal diet with 10, 20, and 30% HPDDG as a replacement for SBM or a combination of FM and SBM, respectively. In trial 1, shrimp (0.18 initial mean weight, 10 shrimp/tank, n=5) were offered diets for six weeks. No significant differences were detected in the growth and feed conversion ratio (FCR). In trial 2, shrimp (1.24 initial mean weight, 30 shrimp/tank, n=4) were offered diets over seven weeks. Significant reductions in growth and FCR were observed when shrimp were fed with diets containing >20% HPDDG. To explore the upper inclusion limit of this product a third trial was conducted for which the basal diet was modified to contain 6, 12, 18, and 24% HPDDG. Shrimp (0.25 initial mean weight, 10 shrimp/tank, n=4) were offered diets over six weeks. Significant reduced growth and increased FCR as well as enhanced iron and copper contents of whole body were detected in treatment containing 24% HPDDG. Apparent net sulfur, calcium, iron, copper, and zinc retention were also significantly affected by different HPDDG inclusions levels. Apparent digestibility coefficients of energy, protein, and amino acid (AA) for the meal were determined using chromic oxide as an inert marker and the 70:30 replacement technique. Generally, nutrients availability of HPDDG were similar to that of FM, while significantly lower than SBM that were evaluated at the same time. Result of this study indicate that HPDDG is a good plant based ingredient and can be included up to 30% as a replacement of SBM without compromising growth of shrimp. When HPDDG was utilized to replace a combination of SBM and FM, an upper limit of 18% of the diet should be recommended in shrimp feed formulation. The growth depression observed at high levels of inclusion is not likely due to digestibility but a limitation of some nutrients (e.g. marginal amino acids). Palatability shifts or unidentified factors could also be factors influencing the negative effects at high levels (≥18% of the diet).