POTENTIAL INTERACTION BETWEEN VITAMIN D AND VITAMIN K IN RELATION TO GROWTH, CALCIUM METABOLISM AND BONE MAINTENANCE IN GILTHEAD SEABREAM JUVENILE Sparus aurata

Introduction

Studies on plant-based ingredients have been increasing for aquafeed production due to the diminished availability and increasing price of high-quality fish meal and fish oils (FAO, 2020). This alternative source of plant-based ingredients may alter the nutritional profile of the produced aquafeed, which directly affects the nutritional requirement of the fish (Francis et al, 2001) including vitamins, which play a major role in growth, health, and reproduction in fish. Vitamin requirements for various fish species have been established in NRC, 2011, but the requirement level for gilthead seabream (Sparus aurata) was still unknown. 

Gilthead seabream is one of the most cultured fish species in the European Union (EU) aquaculture system and contributes around 6.77% of all European aquaculture production (APROMAR, 2020). Even though the production rate is high, the gilthead seabream is often detected with skeletal anomalies during the culture period which affects the production cost, growth, and fish survival rate (Andrades et al., 1996). There are several studies on skeletal anomalies in gilthead seabream based on developmental stage, temperature, genetic background and nutrition (Boglione and Costa, 2011, Izquierdo et al., 2016). Therefore, the present study focused on the micronutrients, especially vitamin D and vitamin K, due to the lack of information about these vitamins on gilthead seabream juveniles.

Vitamin D (VD) and Vitamin K (VK) are fat soluble vitamins, which deliver synergistic effects on calcium (Ca) metabolism, skeletal development, and mineralization of bones. In fish, the source of vitamin D depends on the dietary intake, and it helps in calcium deposition and skeletal development (Lock et al., 2010), while vitamin K helps in posttranslational modification and activation of the vitamin K-dependent proteins, that eventually help in skeletal development of fishes (Krossøy et al., 2011). This suggests a pleiotropic effect in vitamin D and K, that helps in understanding the interaction of these vitamins in growth and skeletal development of fish. Thus, the aim of the study was to evaluate the potential interaction between vitamin D and K in skeletal development and to identify the optimum requirement of these vitamins in gilthead seabream juveniles.

Materials and methods

Seven different isoenergetic and isonitrogenous plant-based diets (FM – 10%, FO – 6%) were formulated with increasing levels of VD3 and VK3 (Table 1). Gilthead seabream juveniles with initial weight of 72.63 ± 0.33 g were randomly distributed into 21 tanks in triplicate groups and manually fed 2% body weight until apparent satiation for 105 days. Every two weeks, fish were sampled for growth parameters such as length and weight. Water quality and feed intake were monitored throughout the experiment. At the end of the trial, fish were analysed for growth performance, protein utilization and body indices. Samples were taken for X-ray, histology, gene expression and vitamin analyses.

Results

After a period of 105 days feeding, fish doubled the weight, in which the final body weight (FBW) showed no significant difference (P – 0.19) among the groups by one-way ANOVA. But with respect to two-way ANOVA the VD*VK interaction showed a significant difference (P – 0.002) between treatments. Other parameters such as Feed conversion ratio (FCR), Specific growth rate (SGR), Feed intake (FI), showed no significant difference in one-way ANOVA as well as no interaction effect (P ≤ 0.05) by two-way ANOVA among the groups, except for Protein efficiency ratio (PER) which showed significant differences among the groups in both statistical tests such as One-way ANOVA: P – 0.04 and  Two-way ANOVA: P – 0.009 (Figure 1).

Discussion and Conclusion

The results from the present study suggest no significant difference in growth performance by one-way ANOVA. However, two-way ANOVA suggests an interaction effect among the groups with respect to FBW. Moreover, there were no significant differences observed in FI by both statistical tests, indicating there might be a combination effect of dietary VD and VK in FBW of the gilthead seabream juveniles. Abawi and Sullivan (1987) also suggest that higher supplemental levels of vitamins D and K would improve growth performance of poultry. On the other hand, in Atlantic salmon (Salmo salar) VD, VK, Ca, and dissolved CO2 exposure did not cause any deleterious effects on bone mineralization or fish health (Graff et al.,2002). Therefore, further analyses are being conducted to understand the interaction effects of these vitamins in skeletal development and calcium metabolism in gilthead seabream juveniles.

Acknowledgment

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 766347

References

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