Abstract
The protein fraction is the most expensive component in aquafeed. This study aimed to determine if injecting fragmented shark (Squalus acanthias) DNA into Nile tilapia (Oreochromis niloticus) broodstock could enhance the offspring's ability to utilize low-protein diets. Shark genomic DNA was used as a donor source to investigate if its high metabolic efficiency and growth traits could biologically complement and improve feed utilization in tilapia fed low-protein diets. A 2 × 3 factorial design was used, where offspring from genetically modified (GM) and wild-type (WT) broodstock were fed diets containing 22%, 26%, and 30% crude protein (CP) for 90 days. Results showed that GM tilapia had significantly superior growth performance (FBW, WG, SGR) and feed utilization (lower FCR; higher PER, PPV) compared to WT (P < 0.05). Critically, GM fish fed the 22% CP diet achieved growth comparable to WT fish fed the 30% CP diet. The GM fish also deposited significantly more body protein and fat, with lower moisture content. Molecular analysis revealed distinct alterations in the muscle protein profile (SDS-PAGE) and a significant metabolic rebalancing of the amino acid profile (higher methionine and valine, but lower lysine and arginine) in GM fish compared to WT fish. The genetic analysis via PCR and sequencing confirmed the successful transfer of the shark's COX1 gene in GM fish and consequently its absence in WT. In conclusion, the direct injection with shark genomic DNA is an effective technique to produce tilapia offspring with enhanced growth and metabolic efficiency, particularly on low-protein diets. This confirmed genetic modification, which alters the proteomic and metabolic profile, offers a viable approach to enhance tilapia aquaculture fed on a low-protein diet.