This study comprised five experiments aimed at evaluating the impact of three natural antioxidants, namely sweet orange peel extracts (SOPE), shaddock peel extracts (SHPE), and lemon peel extracts (LMPE), on the performance, carcass traits, meat quality, and lipid oxidation of broiler chickens. The peels of ripe sweet oranges, shaddock, and lemons were subjected to oven-drying and extracted using standard methods. The qualitative and quantitative phytochemical contents, as well as the diphenyl 2-picrylhydrazyl (DPPH) abilities of SOPE, SHPE, and LMPE, were also assessed.
The phenolic compounds present in SOPE, SHPE, and LMPE were found to include steroids, flavonoids, coumarins, triterpenes, and alkaloids. However, phlobatanin, anthocyanin, and amino acids were not detected. SOPE exhibited significantly higher levels of steroids (34.43 mg/100g), flavonoids (161.82 mg/100g), terpenoids (17.09 mg/100g), triterpenes (128.27μg/100g), and alkaloids (32.44 mg/100g) compared to SHPE and LMPE. SHPE contained significantly higher phenolics (26.76 mg/100g) than SOPE and LMPE, while LMPE had significantly higher tannins (1.74 mg/100g) and coumarins (18.15 μg/100g) compared to SOPE and SHPE.
For the feeding trials, a total of 300 day-old broiler chicks of the Abhor acre breed were divided into five treatments (T) with three replicates each, following a completely randomized design. The feeding trial spanned eight weeks, with the first four weeks utilizing starter diets (23% CP and 2879 Kcal/kg ME) and the remaining four weeks using finisher diets (20% CP and 3000 Kcal/kg ME). The first feeding trial consisted of T1 (butylated hydroxyanisole BHA, 0.02% per liter of water, + control), T2 (water OW as – control), T3 (SOPE), T4 (SHPE), and T5 (LMPE), each at 0.02% per liter of water. The second feeding trial included T1 (BHA as control), T2, T3, T4, and T5 (SOPE at 0.02%, 0.04%, 0.06%, 0.08%, and 0.10% per liter of water, respectively).
In the first feeding trial, LMPE showed superior weight gain (WG) and feed conversion ratio (FCR) compared to the other treatments. Treatment OW exhibited significantly higher (p<0.05) white blood cell (WBC) levels than other treatments, while both SHPE and LMPE treatments had higher (p<0.05) red blood cell (RBC) counts. OW and SOPE treatments resulted in significantly higher (p<0.05) total protein (TP) and cholesterol (TC) levels. LMPE treatment showed higher (p<0.05) carcass weight than other treatments, and sensory evaluations favored SOPE treatment.
Regarding lipid oxidation, TBARS values on day 0 for cooked meat in SHPE treatment and raw meat in OW and SOPE treatments were significantly lower (p<0.05) than other treatments. On storage day 2, TBARS values in SHPE cooked meat were significantly lower (p<0.05) than other treatments, while raw meat storage day 2 TBARS values were similar in BHA, SOPE, SHPE, and LMPE treatments but significantly lower (p<0.05) than OW treatment.
In the second feeding trial, SOPE at 0.04% showed significantly higher (p<0.05) WG and feed intake compared to other treatments, while FCR was similar between BHA and SOPE (0.04% and 0.10%) treatments and significantly lower (p<0.05) for SOPE (0.06% and 0.08%) treatments. SOPE (0.10%) exhibited significantly higher (p<0.05) WBC levels, and SOPE (0.08%) treatment had higher (p<0.05) RBC counts. SOPE (0.06%) treatment resulted in significantly higher (p<0.05) total cholesterol (TC) levels. Carcass weight was higher (p<0.05) in SOPE (0.04%) treatment, and sensory evaluations favored SOPE (0.10%) treatment.
Regarding lipid oxidation in the second feeding trial, TBARS values on day 0 for both cooked and raw meat in BHA and SOPE (0.04% and 0.08%, except for SOPE 0.06%) were significantly lower (p<0.05) than other treatments.
In conclusion, SOPE demonstrated significant effects on various parameters, with better performance observed in birds fed higher doses (0.04%, 0.06%, and 0.10%) of SOPE in the second experimental feeding trial.
The Impact of Supplementation with Natural Antioxidant Extracts on Growth Performance, Carcass Traits, Meat Quality, and Shelf-Life of Broiler Chickens.