Effect of different types of bacterial single cell protein on feed intake, digestibility, growth and body composition of Pacific white shrimp (Penaeus vannamei)

Abstract

This study assessed the potential of four bacterial (Methylococcus capsulatus) single cell protein (SCP) products as alternative protein sources for Pacific white shrimp (Penaeus vannamei) diets. A growth trial and a digestibility trial were undertaken, during which the bacterial SCP products were compared with a high-quality fishmeal and a soy protein concentrate, regarding their impact on ingredient digestibility, growth, feed intake and whole-body composition of juvenile P. vannamei. Seven diets were formulated; one reference diet (REF) and six test diets. The test diets consisted of 85% of the REF diet and 15% of a test ingredient. Ingredients tested were four bacterial SCP products (SCP1–4), which differed in processing conditions, fishmeal (FM) and soy protein concentrate (SoyProt). Growth and feed utilization were similar for P. vannamei fed either the FM diet or one of the bacterial SCP diets, whilst lowest growth and feed utilization were observed for shrimp fed the SoyProt diet. Final whole-body protein content did not differ between shrimp fed the FM diet or one of the four bacterial SCP diets. However, shrimp fed the SCP diets had a significantly higher final phosphorus body content and a higher phosphorus retention than shrimp fed the FM or SoyProt diets. This indicates a higher phosphorus availability in the bacterial SCP products compared to FM and SoyProt. Protein digestibility of the SCP products was similar to FM, whilst amino acid (AA) digestibility was comparable to FM for three of the four SCP products (SCP1, SCP2 and SCP4). The SCP3 product showed the lowest digestibility for most AA, indicating a possible influence of processing conditions on AA availability of bacterial SCPs. Overall, this study highlights that bacterial SCP originating from M. capsulatus is a viable alternative protein source for Pacific white shrimp diets, but processing conditions should be taken into account.