Effect of Some Natural Antioxidants on Growth Performance, Blood Parameters and Carcass Traits of Growing Rabbits Under Egyptian Summer Condition

The current study aimed to evaluate the effect of treatment with combination of royal Jelly (RJ) plus green tea (GT) or propolis (PR) plus GT on thermo-physiological response, growth performance, blood biochemicals and carcass traits. Total of 60 NZW weaned rabbits (5 wk of age and 703.03±11.59 g LBW) were assigned into three similar groups of 20 rabbits in each (10 males and 10 females). Rabbits in the 1and 2 groups were fed complete feed diet (CFD) supplemented with 2 g GT/kg and orally treatment twice/week with 150 mg RJ/kg (G1) or 0.5 g PR/kg LBW (G2). However, rabbits in the 3 group were fed the same CFD without any supplements and orally treated with one ml saline and served as a control group (G3). Throughout the experimental period (August and September months), temperature humidity index (THI), rectal temperature (RT), LBW, feed intake (FI), viability rate and performance index (PI) were recorded, and daily weight gain (DWG) and feed conversion ratio(FCR) were calculated at 5-9, 9-13 and 5-13 age intervals. Blood samples were collected from three males from each group for determination of total proteins (TP), albumin (AL), glucose, cholesterol, triglycerides, high density lipoproteins (HDL), low density lipoproteins (LDL), creatinine, urea, triiodothyronine (T3) and tetraiodothyronine (T4) concentrations, as well as activity of aspartate (AST) and alanine (ALT) transaminases in serum. At 13 wk of age, three males from each group were slaughtered to evaluate carcass traits. Meat samples from hind limb were taken for chemical analysis. Results show that rabbits extremely severed from heat stress throughout all months studied. RT reduced in G2 (P<0.05) and G1 (P≥0.05) as compared to G1, being better in males than in females. Both G1 and G2 showed marked improvement in LBW, DWG, RGR, FI, FCR and PI as compared to G3, being with the best G2, in particular, at 5-9 wk of age. VR was the highest in G1, and higher in females than females only in G2. Concentrations of TP, AL, GL, AL: GL ratio, total cholesterol, triglycerides, LDL, HDL, creatinine and urea as well as activity of ALT in blood serum were not affected by treatment. Serum glucose concentration was higher (P<0.05) in G2 than in G1, while both groups did not varied significantly from that in G1. Also, AST activity in serum reduced (P<0.05) in G1, but did not differ in G2 as compared to G3. Concentration of T3 and T4 was higher (P<0.05) in G1 than in G2 and G3. All carcass traits and meat composition were not affected significantly by treatments. Economic feed efficiency was the best in G1, followed by G2, and the lowest in G3. In conclusion, treatment of weaned rabbits during growing period under summer ambient temperature from 5 to 13 weeks of age with green tea in combination with royal jelly or propolis twice/week resulted in improving growth performance, viability rate and economic feed efficiency without adversely effects on rabbit health, in particular, at 5-9 wk age interval. A combination of royal jelly with green tea showed the best results.