Stable isotope profiling of farmed Penaeus monodon for the evaluation of feed efficiency

The current study profiled the dual isotopes of carbon and nitrogen in feeds and muscles of farmed Penaeus monodon for evaluation of feed efficiency in making up the prawn muscle. Signatures of both feed and resulted muscles of P. monodon were subjected to two- and three-source linear mixing models to elucidate the contribution of each feed item in the building of the muscle. The results revealed that carbon and nitrogen in different feed substances have different influences on the growth and nutrient uptake by the prawn. Different growth stages showed isotopic switching within prawn muscles in the course of their building up. Generally, marine sources were the most enriched in both δ¹³C and δ¹⁵N. Likewise, δ¹³C of wild-caught prawns (−16.30 ± 0.72‰) were superior over farmed prawns (−18.00 ± 0.59‰) (p < 0.01), whereas no significant differences were observed in δ¹⁵N values between wild (8.03 ± 0.65‰) and farmed (8.38 ± 1.39‰) (p > 0.01). The isotopic composition of P. monodon mirrored those of the ingredients contained in its feed and varied across treatment levels. Comparing to other ingredients, marine macroalgae exhibited significantly higher (p < 0.01) feed efficiency, and as a result, they improved the growth of P. monodon compared to the other ingredients. The same treatment recorded significantly lower (p < 0.01) feed conversion ratio compared to other treatments. However, muscle somatic index, specific growth rate and condition factor were not significantly different across treatments (p > 0.01). Moreover, a clear distinction was observed between wild and farmed P. monodon, and such a distinction is clearly explained by δ¹³C composition. In conclusion, multiple sources of δ¹³C and δ¹⁵N in feeds are incorporated more efficiently in muscles than single sources.