Evaluation of single cell protein on the growth performance, digestibility and immune gene expression of Pacific white shrimp, Penaeus vannamei

Growth and digestibility trials were undertaken to evaluate a single cell protein (SCP) produced from methane-oxidising bacteria Methylococcus capsulatus (String Bio, Bengaluru, India) as a replacement for fishmeal in the diets of Pacific white shrimp, Penaeus vannamei. Five isonitrogenous and isoenergetic diets were formulated to contain different levels of SCP: Control (Fishmeal, no SCP), SCP inclusion at 50 g/kg (S-5), 100 g/kg (S-10), 200 g/kg (S-20), 250 g/kg (S-25). The final body weight of the shrimp increased with increasing levels of SCP up to 200 g/kg (S-20) and recorded the best feed efficiency when compared to other treatments. Nitrogen (N) and phosphous (P) gain and retentions were improved in shrimp fed diets containing upto 200 g/kg SCP. There was no significant difference in the whole-body chemical and amino acid composition of shrimp. Apparent protein digestibility of the SCP was greater than 0.90. The expression levels of immune-relevant genes (lysozyme, Toll-like receptor and immune deficiency (IMD)) were up-regulated in the shrimp fed diet S-20. Results of this work demonstrate that SCP from M. capsulatus can be efficiently used in the diet of P. vannamei up to 200 g/kg (two-thirds of fishmeal replacement) with significant beneficial effects on growth, feed and nutrient utilisation.