Dietary Zinc Requirement of Oreochromis aureus and Effects of Dietary Calcium and Phytate on Zinc Bioavailability

Abstract

Two experiments were conducted to determine the dietary zinc requirement of fingerling blue tilapia (Oreochromis aureus) and the effects of dietary calcium and phytate on zinc bioavailability. Purified egg white diets containing graded levels of supplemental zinc were fed to fingerling tilapia in triplicate aquaria for 80 days. No overt signs of zinc deficiency were observed; however, scale and bone zinc concentrations of fish fed the various diets were significantly (P < 0.05) affected and increased linearly as dietary zinc increased until plateauing at 20 mg Zn/kg diet and greater. Based on these data, 20 mg Zn/kg of dry diet was determined to be the minimum dietary zinc requirement of blue tilapia. Purified egg white diets containing 20 mg Zn/kg were also supplemented with 0.5 or 2.0% calcium and 0 or 1.5% phytate in a factorial arrangement to determine the effects of these dietary factors on zinc bioavailability. At this level of supplemental zinc, 1.5% phytate significantly (P < 0.05) reduced zinc bioavailability as reflected in scale and bone zinc concentrations; whereas, dietary calcium did not affect zinc bioavailability. Results from this study establish the dietary zinc requirement of blue tilapia and indicate that higher levels of supplemental zinc should be included in practical feeds to compensate for reduced zinc bioavailability caused by dietary phytate.

Comparison of endogenous loss and maintenance need for minerals in rainbow trout (Oncorhynchus mykiss) fed fishmeal or plant ingredient-based diets

“…We did not measure phytic acid content, but based on ingredient composition of the two feeds, we estimated diet M to contain no phytic acid and diet V to have about 0.27 % of phytic acid. It has been often observed that apparent digestibility of dietary Zn is reduced by phytic acid or calcium phytate or even by supplementation of inorganic calcium and phosphorus salts (Richardson et al 1985;Hardy and Shearer 1985;McClain and Gatlin 1988;Gatlin and Phillips 1989;Satoh et al 1989;Ramseyer et al 1999;Kousoulaki et al 2010;Antony Jesu Prabhu et al 2014a). This may explain the increased loss of dietary as well as endogenous Zn in fish fed diet V compared with diet M. Moreover, ELF of K (P = 0.11) and Mg (P = 0.15) also tended to be slightly higher in trout fed diet V, as reported in piglets when fed diets containing phytic acid (Woyengo et al 2009).…”

Essential fatty acid requirement of juvenile red drum (Sciaenops ocellatus)

“…The 7% tristearin and menhaden oil diets were used again as EFA-deficient and control diets, respectively. Procedures for diet preparation were as previously described (McClain and Gatlin 1988). In addition, all diets were supplemented with 125 mg ethoxyquin/kg.…”

Dietary zinc requirement of adult Nile tilapia (Oreochromis niloticus) fed semi-purified diets, and effects on tissue mineral composition and antioxidant responses

“…The dietary Zn requirement of tilapia also had been studied (Do Carmo et al, 2004, 2005Eid and Ghonim, 1994;Lin et al, 2008;McClain and Gatlin, 1988). The tilapia in these previous studies were of small size (average initial body mass less than 5 g), whereas the Zn requirement of large tilapia has received little attention.…”