Encapsulated L-Lysine: from physicochemical properties to broiler responses

Precision nutrition in broiler production requires optimizing amino acid bioavailability while minimizing nitrogen excretion. Therefore, this study was conducted to evaluate the effects of dietary micro-encapsulated L-lysine on growth performance, feed efficiency, carcass traits, and selected blood metabolites in broiler chickens. A total of 600 one-day-old Arian broiler chicks were used in a completely randomized design with six dietary treatments, five replicates per treatment, and 20 birds per replicate. The treatments consisted of a control diet formulated to meet the recommended lysine requirement using conventional L-lysine HCl, and five diets in which micro-encapsulated L-lysine (EL) supplied 100%, 90%, 80%, 70%, and 60% of that in the control diet. The physicochemical properties of EL were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Field Emission Scanning Electron Microscopy (FESEM). FTIR and DSC analyses confirmed successful core-shell integration, showing a reduction in melting enthalpy from 107.9 to 83.37 J/g, indicating a transition toward a more stable matrix-type structure. Morphological analysis revealed a heterogeneous porous architecture with surface microcracks. Biological results showed that EL had no significant effect on final body weight or feed intake (P > 0.05). However, birds fed diets containing 80-100% EL exhibited a significantly lower feed conversion ratio (FCR) during the starter period (1-28 d) (P < 0.05). Additionally, EL at 70-80% levels increased HDL-cholesterol and reduced serum globulin concentrations compared with the control (P < 0.05). These findings indicate that micro-encapsulated L-lysine may improve feed efficiency during early growth and can partially replace crystalline lysine in broiler diets without negatively affecting carcass characteristics.