Effect of fortification of potassium and magnesium in the diet and culture water on growth, survival and osmoregulation of Pacific white shrimp, Litopenaeus vannamei reared in inland ground saline water.

Abstract

A 60 day trial was conducted to evaluate the effect of dietary supplementation of graded levels of potassium (K+) and magnesium (Mg2+) on Litopenaeus vannamei reared using IGSW (inland ground saline water, 10 ppt). Two different types of waters, IGSW without ionic fortification (R-IGSW, R-raw) and IGSW fortified with K+ & Mg2+ (F-IGSW, F-fortified) with equivalent salinity sea water was used. Four experimental diets with graded levels of K+ & Mg2+: F1 (5 g KCl & 150 mg MgCl2 kg-1 of feed); F2 (10 g KCl & 300 mg MgCl2 kg-1 of feed); F3 (15 g KCl & 450 mg MgCl2 kg-1 of feed) and F4 (with no ionic amendment) were tested in the trial, for each of the two types of water. A significant improvement in the growth and survival has been observed in the groups fortified with K+ & Mg2+ in the feed (P<0.05) irrespective of the potassium and magnesium levels in the water. No significant difference in osmoregulatory capacity, serum and water osmolality and Na+ K+ATPase activity of gill despite the significant variation (P<0.05) in serum K+, Na+, Mg2+ and Ca2+ levels were observed among different treatments. It is concluded that growth and survival of L. vannamei can be enhanced by supplementing the deficient ions such as K+ (5 g kg-1) and Mg2+(150 mg Kg-1) through diet as well as in the water simultaneously.