Diets containing purified nucleotides reduce oxidative stress, interfere with reproduction, and promote growth in Nile tilapia females
Introduction
Aquaculture is fast expanding worldwide and its current growth rates are higher than those of other farming activities (FAO, 2018). In this context, tilapia is the second most farmed group of fish in the world and tilapia farming has increased 11% annually in the last three decades, reaching 5.9 million tons in 2017 (Barroso et al., 2019). Nile tilapia (Oreochromis niloticus) is the most important species of this group (FAO, 2018) and is farmed in at least 78 countries, with 4.13 million tons produced in 2017 (Cai et al., 2019).
With the accelerated growth of this activity, the intensification of production systems has been adopted as a strategy to ensure productivity meets the demands of the market (Barroso et al., 2018). However, in some countries the production chain has not developed at the same speed that the tilapia culture has increased, and the availability of high-quality, vigorous and resistant fry has become a limiting factor in the production of tilapia (Schulter and Vieira Filho, 2017; Barroso et al., 2018; FAO, 2018).
Thus, the strategies of feeding and the nutritional management of female and male breeders (Bhujel et al., 2007; Bombardelli et al., 2017) may be alternatives that contribute to improving the quality of eggs, larvae, and fry (Izquierdo et al., 2001; Migaud et al., 2013). Nutrition is especially important in females because dietary nutrients are recruited for vitellogenesis (Mommsen and Korsgaad, 2008; Fernández-Palacios et al., 2011) and influence gonadal maturation and yolk quality (Bobe and Labbé, 2010; Hilbig et al., 2019). This determines the vigor and quality of the offspring (Bombardelli et al., 2009; Ng and Wang, 2011), because the embryos and larvae in the initial stage of development depend solely on the yolk for feeding (Mazorra et al., 2003; Fernández-Palacios et al., 2011). Moreover, nutrition modulates the health and vigor of females and determines their ability to tolerate the metabolic stress imposed by the intense reproduction process and rearing characteristics of tilapia (Lupatsch et al., 2010).
Dietary supplementation with purified nucleotides (NT) may be a good approach for improving the health and vigor of Nile tilapia broodstock. These molecules are components of nucleic acids, DNA and RNA (Hess and Greenberg, 2012), and are involved in the coding/decoding of genetic information, as well as in processes of cell growth and repair, and the regulation of several metabolic pathways (Cosgrove, 1998; Hess and Greenberg, 2012). Even if an organism is able to synthesize the nucleotides via the de novo pathway or via cell turnover (Li and Gatlin III, 2006), under highly challenging conditions that cause cellular or metabolic stress, external supplementation may be necessary (Hess and Greenberg, 2012).
Research in this area has been conducted with fish in the growth phase and for short periods of time (Cheng et al., 2011; Kenari et al., 2013; Peng et al., 2013; Barros et al., 2015; Shiau et al., 2015; Xu et al., 2015). Data on dietary supplementation with NT in fish broodstock and its effects on the quality of the offspring are scarce. Only one preliminary study conducted by González Vecino (2005) suggested that dietary supplementation with NT improves fecundity, egg quality, and larval survival in haddock broodstock (Melanogrammus aeglefinus L.).
Thus, the objective of the present study was to assess the health, growth, and reproductive performance of Nile tilapia (O. niloticus) females fed diets containing purified NT. The effects on hematological, biochemical, and morphological parameters would be assessed, in addition to indicators of immune system function and redox balance.
Section snippets
Animals, facilities, and experimental design
The study was conducted using the procedures approved by the ethics committee on the use of animals of the West Paraná State University (CEUA/Unioeste), according to protocol no. 2112/2016. A total of 420 females (average weight of 286 ± 7.15 g) and 140 males (average weight of 536 ± 13.4 g) of Nile tilapia (GIFT strain) were used. The females were conditioned in 20 hapas (2 m × 3 m; 1 mm mesh net), resulting in 21 females per hapa. The males were conditioned in others 20 hapas (1 m × 2 m; 2 mm
Reproduction and growth
Along the entire experimental period females and males mated eight times. The fecundity of spawning females (eggs g−1 of spawning female) was significantly higher (p < .05) among those fed diets containing 7.5 g NT kg−1 (Table 2). On the other hand, the percentage of spawning females significantly decreased (p < .05) among the females given rations containing 7.5 g and 10.0 g NT kg−1 (Table 2). Consequently, the relative eggs production (eggs g−1 of mated female) of all individuals in the mated
Discussion
Feeding Nile tilapia females with diets containing NT had an effect on reproduction and energy metabolism, and improved the body function and the health of the female breeders. Nucleotide supplementation to fish diets (Burrells et al., 2001; Tahmasebi-Kohyani et al., 2011; Hossain et al., 2016; Guo et al., 2017; Samir et al., 2017) and shrimp diets (Li et al., 2007b; Arshadi et al., 2018) has been shown as an important strategy to improve animal health and growth. However, some studies have
Conclusions
Dietary supplementation with purified nucleotides interfered with energy metabolism, redox balance, and liver and gonadal function in breeding Nile tilapia females. This translated into improvements in their health and, consequently, reproductive and growth rates of females fed diets containing between 5.0 and 7.5 g NT kg−1.
Declaration of Competing Interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
We thank NutriQuest-Technofeed for donating the Ascogen®, Piscicultura Sgarbi, and specifically thank Ari Sgarbi and Ariane Sgarbi for donating the tilapia broodstock used in the experiments. We also thank the national Scientific and Technological Development Council (CNPq) for financially supporting the study through grants CNPq no. 311658/2016–4 and no. 429239/2016–5.
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