Dietary supplement guava leaf extract regulates growth, feed utilization, immune function, nutrient digestibility and redox regulation in growing rabbits

The use of agricultural waste in animal production has gained global interest. An eight-week trial was conducted to investigate the impacts of adding ethanolic guava leaf extract (GLE) as a feed supplement on the growth, feed utilization, immune response, nutrient digestibility, redox regulation, and blood health of growing rabbits. Ninety weaned growing rabbits were randomly assigned to three groups. The first group was fed a basal diet (GLE0), while the other two groups were fed the control diet fortified with 15 mg (GLE15) or 20 mg (GLE20) of GLE per kg of diet for 8 weeks. The HPLC analysis of GLE exhibited the presence of gallic acid, ferulic acid, catechin, and caffeic acid in significant amounts. The results indicated that final body weight, daily body weight, daily feed intake and nutrient digestibility were significantly higher in the GLE-treated groups compared to the un-treated group (p < 0.05). Dietary supplementation of GLE significantly reduced lipid contents including triglycerides, total cholesterol, LDL, HDL, and VLDL (P < 0.05), with the most significant results observed when adding 20 mg/kg to the diet. AST and ALT levels as well as cortisol hormone in rabbits fed GLE were lower than those in the GLE0 group (P < 0.05). Immunoglobulins (IgG and IgA), antioxidant biomarkers (SOD and TAC) and T3 hormone were significantly improved by GLE supplementation (P < 0.001). Rabbits fed with GLE had lower levels of ROS and MDA compared to those in the GLE0 group (P < 0.001). Moreover, the hepatic and intestinal architectures were maintained in all rabbits fed diets with GLE. The results suggest that GLE supplementation (20 mg/kg diet) in fattening rabbit diets could efficiently improve growth, health status, blood physiology, antioxidant capacity and tissue histology.