Appropriate zinc requirements of Litopenaeus vannamei under low-salinity cultivation estimated by biokinetic modeling

The Pacific white shrimp (Litopenaeus vannamei) has become a popular species in low-salinity aquaculture in China, while its production efficiency remains limited compared to marine systems. Zinc (Zn), an essential mineral element, plays a critical role in shrimp growth. In the present study, we employed the stable isotope ⁶⁸Zn as a tracer to quantify Zn accumulation dynamics in L. vannamei reared at 5 ppt salinity. An optimized biokinetic model was developed to determine the precise Zn requirements in low-salinity conditions. The results demonstrate that dietary uptake made more contribution to Zn assimilation (>50 %) than waterborne uptake under environmentally relevant dissolved Zn concentrations (5–20 μg L⁻¹). The biokinetic model estimated a daily net Zn flux of 1.16–1.27 μg g⁻¹ d⁻¹, corresponding to an appropriate dietary Zn concentration of 44–66 mg kg⁻¹ at ingestion rates of 2–3 %. These predictions were validated by a 30-day feeding trial, where shrimp fed diets supplemented with 40–80 mg kg⁻¹ Zn exhibited significantly improved growth performance and physiological responses (e.g., digestive and antioxidant enzyme activities). Overall, this study provides a mechanistic framework for optimizing Zn supplementation in shrimp feeds. The biokinetic approach offers an alternative to traditional methods, with broader applications for precise mineral nutrition.