Dietary curcumin encapsulated in nanostructured lipid carriers improves growth performance, feed utilization efficiency, and resistance to <em>Streptococcus agalactiae</em> in Nile tilapia (<em>Oreochromis niloticus</em>).

BACKGROUND AND AIM: Streptococcosis caused by Streptococcus agalactiae represents a major constraint to Nile tilapia (Oreochromis niloticus) aquaculture, resulting in substantial economic losses. Curcumin (CUR) possesses antioxidant, antimicrobial, and immunomodulatory properties, but its practical application is limited by poor aqueous solubility and low bioavailability. This study aimed to develop CUR encapsulated in nanostructured lipid carriers (CUR-NLCs) and evaluate their effects on growth performance, feed utilization efficiency, and resistance against S. agalactiae infection in Nile tilapia.

MATERIALS AND

METHODS

CUR-NLCs were synthesized using a phase-inversion compositional technique and characterized for particle size, polydispersity index, zeta potential, encapsulation efficiency, and release behavior. A 60-day feeding trial was conducted using four dietary treatments: a control diet, a free CUR diet (2000 mg/kg feed), CUR-NLCs containing an equivalent amount of CUR, and blank nanostructured lipid carriers. Growth performance, feed utilization indices, hepatosomatic index, and length-weight relationships were evaluated. Antibacterial activity against S. agalactiae isolates was determined, followed by experimental challenge with strain ENC06 to assess survival responses.

RESULTS

CUR-NLCs exhibited favorable physicochemical characteristics, including a mean particle size of 215.6 nm, a low polydispersity index (0.145), and a high encapsulation efficiency (98.79%), along with sustained-release properties. CUR-NLCs produced larger inhibition zones against S. agalactiae than free CUR. Fish receiving the CUR-NLC diet demonstrated significantly higher final body weight, weight gain, specific growth rate, feed intake, and protein efficiency ratio than the control group (p < 0.05). Positive allometric growth (b = 3.278) and improved relative condition factor were observed in CUR-NLC-fed fish. Following bacterial challenge, CUR-NLC supplementation resulted in the lowest mortality (11.1%), highest survival (88.9%), and highest relative percent survival (82.4%). Cox proportional hazards analysis indicated an approximately 86% reduction in mortality risk compared with infected controls.

CONCLUSION

Dietary administration of CUR encapsulated in nanostructured lipid carriers improved growth performance, feed utilization efficiency, and post-challenge survival of Nile tilapia. These findings demonstrate that CUR-NLCs represent a promising phytobiotic-based nutritional strategy for enhancing fish health and promoting sustainable tilapia aquaculture.