Benefits of adjusting zinc levels and source in shrimp feed: Your zinc choice may be limiting performance

by Cláudia Figueiredo-Silva, Zinpro, USA

Zinc (Zn) was identified as an essential human micronutrient in 1961. Zn deficiency symptoms include growth retardation, immune insufficiency, chronic inflammation, skin abnormalities, impairment of wound healing, persistent diarrhea, loss of appetite and brain dysfunctions, among others, in both humans and animals.

In addition, Zn is a structural constituent of ∼750 Zn-finger transcription factors enabling gene transcription and is a catalytic component of approximately 2,000 enzymes, encompassing all six classes (hydrolase, transferase, oxido-reductase, ligase, lyase, and isomerase). Hence, Zn is essential for cellular processes, including growth and development, as well as DNA synthesis and RNA transcription.
 

Although information on Zn functions in aquatic species is limited, the basic metabolic functions of trace minerals (TMs) and particularly Zn are recognised to be similar across species (NRC, 2011). Zn is known to exert beneficial effects beyond growth performance, such as bone and nervous system development, improvements in reproduction, reductions in oxidative stress and increased resistance to disease in fish and shrimp.

A common cause of Zn deficiency is malnutrition. Illness and/or infection and high phytate-containing diets reduce Zn bioavailability by inhibiting uptake. The replacement of fish meal (FM) in aquaculture diets may significantly reduce the Zn content while increasing levels of anti-nutritional factors, e.g. phytic acid.  Phytic acid may bind TMs and make them less available for absorption, with direct effects on performance. As supplements, mineral amino acid (AA) complexes have an absorption advantage over inorganic minerals, because they are minimally antagonised by dietary components like phytic acid and use AA-transporters instead of common metal ion transporters (Gao et al. 2014; Sauer et al. 2017).

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The Aquaculturists

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