Diets containing purified nucleotides reduce oxidative stress, interfere with reproduction, and promote growth in Nile tilapia females

Abstract

The objective of the present study was to assess the health, growth, and reproductive performance of Nile tilapia females fed diets containing purified nucleotides (NT). A total of 420 females (286 ± 7.15 g) and 140 males (536 ± 13.4 g) were used. Fishes were fed with extruded rations (280 g of digestible protein kg−1; 11.72 MJ of digestible energy kg−1) containing 0.0, 2.5, 5.0, 7.5, and 10.0 g NT kg−1 for 150 days. After mating occurred in hapas, the eggs were harvested and incubated. At the end of the experiment, blood and tissue samples were collected for hematological, biochemical, morphological, and centesimal composition analyses. In addition, indicators of immune system function and redox balance were analyzed. The production of eggs g−1 by spawning females was significantly the highest at 7.5 g NT kg−1. The percentage of spawning females was significantly low in the 7.5 g and 10.0 g NT kg−1 groups, reflecting on fecundity. However, these females showed significantly the highest growth rates. Diets containing 5.0, 7.5, and 10.0 g NT kg−1 significantly increased hemoglobin levels. Plasma alanine aminotransferase (ALT) significantly decreased in fish fed diets containing between 2.5 and 7.5 g NT kg−1, whereas alkaline phosphatase (ALP) and plasma triglyceride levels significantly decreased with 7.5 g NT kg−1. Levels of NT higher than 5.0 g NT kg−1 led to a significantly increase of albumin and significantly reduced plasma calcium levels. Liver glycogen levels significantly increased with 5.0 g NT kg−1. The activities of liver superoxide dismutase (SOD) and glutathione S-transferase (GST) were significantly the highest in the 5.0 g NT kg−1 and 7.5 g NT kg−1 groups, respectively. The highest glycogen content in the ovaries was significantly observed with 7.5 g NT kg−1. Lipid peroxidation (LPO) in the ovaries was significantly lower with 2.5, 7.5, and 10.0 g NT kg−1, and the highest catalase activity was significantly observed with 2.5 and 7.5 g NT kg−1. Lysozyme activity in the spleen and kidney and levels of nitrite/nitrate in the kidney were not significantly altered. Only the levels of spleen nitrite/nitrate significantly decreased at 10.0 g NT kg−1. Rations containing more than 5.0 g NT kg−1 significantly increased the percentage of secondary growth oocytes, and liver and intestinal morphology was not significantly altered. Diets containing 5.0 g NT kg−1 significantly increased crude protein content in the ovaries. Supplementation with purified nucleotides, using rations containing between 5.0 and 7.5 g NT kg−1, affected energy metabolism, redox balance, and liver and gonadal status in tilapia females, thereby improving their health and, consequently, their reproduction and growth rates.