Enhanced Growth and Immune Response in Common Carp Fry ( Cyprinus carpio ) Treated With a Novel Growth Hormone‐Releasing Peptide Analog (F5WAC)

Growth hormone (GH)‐releasing peptides (GHRPs) regulate growth and immune responses in fish, offering potential aquaculture applications. This study evaluated the effects of GHRP‐6 and its recombinant analog, F5WAC (acetylation of the N‐terminal Histidine [His1] and substitution of D‐Phenylalanine with D‐Tryptophan at position 5), on growth performance, immune function, and metabolic parameters in common carp fry ( Cyprinus carpio ). Peptides (GHRP‐6 and F5WAC) were administered at 100 μg/kg feed over 4 weeks. F5WAC significantly elevated GH levels, cortisol, and immune markers (IgM, C3, and lysozyme activity), alongside upregulated igf1 gene expression, compared to GHRP‐6 and controls. Furthermore, F5WAC‐treated fry exhibited superior weight gain, feed conversion ratio (FCR), and specific growth rate (SGR). These results position F5WAC as a potent growth and immune enhancer, with promising applications in sustainable aquaculture practices.