Structural Equation Modeling (SEM) of the interaction between cholecalciferol treatment and external factors in the incidence of vertebrae malformations in the hybrid grouper Epinephelus fuscoguttatus X Epinephelus polypehadion

Abstract

Vitamin D3(VD3), also known as cholecalciferol plays a crucial role in maintaining calcium and phosphate homeostasis and has the potential to suppress bone malformations in fish larvae. However, external factors during growth also significantly influence the development of fish larval bones. Understanding the complex interaction between VD3 treatment and these external factors is crucial for optimizing therapeutic potential and effectively treating bone anomalies. SEM (Structural Equation Modeling) offers a comprehensive framework to explore these interactions by considering multiple variables simultaneously and examining their interrelationships. This study aimed to determine the impact of VD3 and its relationship with other external factors on the incidence of bone malformations in hybrid grouper larvae (Epinephelus fuscoguttatus X Epinephelus polyphekadion, EFEP). The treatments included a dose of 1.9 IU/g of VD3 in the feed and control group without VD3. All treatments received standard enrichment ingredients including vitamin C, taurine, and commercial enrichment (*SELCO). The enrichment was applied to rotifers (3 – 25 days after hatching, DAH) and artificial feed (25 – 35 DAH). The treatment was conducted in two batches, during the dry season (batch 1) and the rainy season (batch 2), to explore the seasonal impact on bone malformations. Results indicated that VD3 reduced the incidence of bone malformations in EFEP hybrid grouper fry by 1.14–1.65 times. SEM analysis revealed that spawning timing, egg quality, and water quality significantly impacted the occurrence of bone deformities, influencing malformations directly and indirectly through bone mineral content. This study demonstrated that bone malformations can be result from deficiencies in calcium, excess potassium and sulfur, and the presence of bromine in bone.