Introduction
The study explores the use of calcifediol, a metabolite of vitamin D3, as a dietary supplement in gilthead seabream (Sparus aurata). Vitamin D is an essential fat-soluble vitamin that fish are unable to synthesize and so require absorbing it directly from the diet (Lock et al., 2010). While vitamin D3 is commonly used in aquaculture, its metabolite, calcifediol, has shown promise in livestock and rainbow trout (Oncorhynchus mykiss) (Atencio et al., 2005; Rider et al., 2023), but remains untested in marine species like seabream. Given the essential role of vitamin D in calcium homeostasis, bone development, and nutrient absorption (Lock et a., 2010; Sivagurunathan et al., 2022), this research aims to evaluate the effects of calcifediol on growth, biochemical composition, skeletal anomalies, and intestinal histology in seabream juveniles.
Materials and Methods
A total of 600 seabream juveniles (12.8 ± 1.5 g) were divided into five dietary groups with increasing levels of calcifediol: <2.0 (control), 99.7, 167.4, 298.6, and 825.4 ppb. All diets included 3000 IU/kg of vitamin D3. The fish were reared for 15 weeks under controlled conditions and fed three times daily. Parameters measured included growth performance, feed conversion ratio (FCR), specific growth rate (SGR), biochemical composition, vitamin and mineral content, skeletal anomalies (via X-ray), and intestinal histology among others. Statistical analyses included ANOVA and regression models to determine significance (p<0.05).
Results
-Growth Performance: Fish fed 99.7 ppb calcifediol showed the highest growth and best FCR. Higher doses (298.6 and 825.4 ppb) reduced growth, suggesting potential toxicity.
-Biochemical Composition: Whole-body lipid content increased with calcifediol, while protein content decreased. Liver lipid levels rose linearly with supplementation. The whole-body omega 3/ omega 6 ratios describe a higher deposition of DHA and omega 3 in the diet containing 99.7 ppb of calcifediol, whereas the contrary was observed for fish fed the highest level of calcifediol.
-Vitamin and Mineral Content: Whole-body vitamin D3 and vertebral calcium increased significantly at 99.7 and 167.4 ppb. Excess supplementation reduced calcium retention.
-Skeletal Anomalies: No significant differences were observed among groups.
-Histology: Mid-intestine fold length and goblet cell density improved at 99.7–167.4 ppb. Lamina propria width was thinner in supplemented groups, indicating better gut health.
Discussion
Calcifediol supplementation at 99.7 ppb significantly enhanced growth, nutrient retention, and intestinal morphology, outperforming traditional vitamin D3. However, higher doses led to reduced growth and calcium retention, indicating a narrow safety margin. The findings align with previous studies showing vitamin D3 toxicity at high levels in seabream (Sivagurunathan et al., 2022). The improved omega-3/omega-6 ratio and DHA deposition at optimal calcifediol levels suggest enhanced lipid metabolism. Histological improvements, such as increased goblet cells and reduced lamina propria width, support better gut health and nutrient absorption.
Conclusions
Calcifediol is a potent and efficient vitamin D source for gilthead seabream juveniles. A supplementation level of 99.7 ppb optimizes growth, feed efficiency, vitamin D3 retention, and intestinal health. However, excessive levels (>298.6 ppb) may induce toxicity, reducing performance and mineral retention. These results highlight the importance of precise dosing when using calcifediol in aquaculture diets.
References
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Cheng, K., Huang, Y., Wang, C., Ali, W., & Karrow, N. A. (2023). Physiological function of vitamin D3 in fish. Reviews in Aquaculture, 15(4), 1732-1748.
Lock, E. J., Waagbø, R., Wendelaar Bonga, S., & Flik, G. (2010). The significance of vitamin D for fish: a review. Aquaculture nutrition, 16 (1), 100-116.
Rider, S., Verlhac-Trichet, V., Constant, D., Chenal, E., Etheve, S., Riond, B., ... & Schoop, R. (2023). Calcifediol is a safe and effective metabolite for raising vitamin D status and improving growth and feed conversion in rainbow trout. Aquaculture, 568, 739285.
Sivagurunathan, U., Dominguez, D., Tseng, Y., Eryalçın, K. M., Roo, J., Boglione, C., ... & Izquierdo, M. (2022). Effects of dietary vitamin D3 levels on survival, mineralization, and skeletal development of gilthead seabream (Sparus aurata) larvae. Aquaculture, 560, 738505.