Dietary potassium partially compensates the requirement of aqueous potassium of P. vannamei reared in medium saline inland groundwater

Abstract

A 15-day trial was conducted to determine the effect of dietary potassium on the requirement of aqueous potassium in P. vannamei under inland saline water (ISW). Two experimental diets viz. control (C) and control with 1% KCl (K) were fed to P. vannamei as six treatments viz. FW (reared in freshwater and fed on C), ASW (reared in artificial seawater and fed on C), ISW (reared in inland saline water and fed on C), ISW+eK (reared in potassium fortified ISW and fed on C), ISW+fK (reared in ISW and fed on K) and ISW+½eK+fK (reared in 50% K fortified ISW and fed on K). The samples were collected on selected intervals (0th day, 1st day, 7th day and 15th day), and mortality was recorded continuously. Total mortality (100%) was observed in FW and ISW. 100% survival was recorded in ASW and ISW+½eK+fK, while a lower survival was observed in ISW+fk. The haemolymph osmotic and ionic concentrations were lowest in FW and ISW. The principal ions (Na+, K+ and Cl−) and osmolality of ISW+½ eK+fK were restored to the level of ASW within 15 days. Na+K+ATPase activity was increased in ISW while lowered by K supplementation. HSP70 expression was upregulated in ISW fortified with K partially or entirely. However, the groups reared in ISW and ISW supplemented with feed potassium alone could not enhance HSP protection up to the level of ISW+eK and ISW+½ eK+fK groups. Overall, 50% of aqueous potassium can be compensated with 1% dietary KCl, without affecting survival and ionic homeostasis.