Cholecalciferol (vitamin D3) is traditionally used as a vitamin D supplement in aquaculture feed. Once ingested by the fish, two steps of hydroxylation using hydroxylase enzymes are necessary to convert cholecalciferol, via calcifediol (25-OH-D3) into calcitriol (1,25-OH-D3). By supplementing the feed directly with Bio D® (calcifediol), one of the two hydroxylation processes is avoided, improving the activity of the vitamin.
There is evidence to suggest that direct dietary calcifediol supplementation in higher vertebrates is effective at promoting performance, improving bone mineralisation, and reducing the incidence of tibial dyschondroplasia (Atencio et al., 2005; Han et al., 2016) and modulating avian immunity (Gómez-Verduzco et al., 2013; Leyva-Jiménez et al., 2019; Hashim et al., 2022). However, this had not been tested in Mediterranean aquaculture species until the present work which shows the first evidence of the positive effects of this compound on juvenile sea bream.
Materials and method
In this study, 360 juvenile sea bream (Sparus aurata), weighing 12.8 ± 1.5 g were distributed across nine tanks in groups tripled per diet, and fed either a control diet or one of two diets containing different levels of Bio D (99.7 and 167.4 ppb). Feeding was until apparent satiety three times a day for 105 days under a natural photoperiod (12 hours of light).
At the end of the trial, feed conversion rate (FCR), specific growth rate (SGR) and fish proximal composition were calculated.
Results and discussion
At the end of the trial, fish fed the diet containing 99.7 ppb of Bio D (calcifediol) showed the highest weight, which was significantly higher than the control group (Table 1) and led to a higher biomass production.
Fish had a total weight gain of up to 528.9 ± 27.3 (%) at the end of the trial, although this was not significantly different between treatments (Table 2). The lowest FCRs were observed in the fish fed diets containing Bio D, also leading to better feed performance.
An increase in vitamin D3 content in the fish was observed associated with the increase in Bio D in the diet. The calcium content in the vertebrae increased to the level of 99.7 and 167.4 ppb (Table 3). Better calcium retention plays a key role in skeletal mineralisation and is linked with bone strength and growth in fish.
Conclusion
- The inclusion level of 99.7 ppb of Bio D is recommended to improve growth, FCR and calcium levels in the vertebrae.
- Calcium content of bone increases with the use of Bio D at 99.7 and 167.4 ppb. Calcium plays a key role in normal bone development, potentially leading to fewer skeletal deformities and normal growth.
