The present study aimed to investigate the influence of the dietary antioxidant addition to the basal diet on productive and reproductive performance of Mandara strains under summer conditions. A total number of 147 laying hens and 21 cocks at 24 weeks of age was allocated to 7 treatment groups (21 hens + 3 cocks / each treatment) until 36 weeks of age. The birds within each treatment were fed as follows:T1: Basal diet only without supplementation (served as a control), T2: Basal diet and 100 mg Vitamin C /kg feed, T3: Basal diet + 100 mg Vitamin E /kg feed, T4: Basal diet + 100 mg Vitamin C + E /kg feed, T5: Basal diet + 200 ml rosemary oil /kg feed, T6: Basal diet + 200 ml oregano oil /kg feed and T7: Basal diet + 100 ml rosemary and oregano oils as medicinal plants /kg feed, respectively.
The obtained results showed that, the major percentage components of rosemary and oregano oils by Gas chromatography-mass spectrometry (GC—MS) analysis were 1.8-cineole (44.33), α-Pinene (16.38) and Carvacrol (65.41) and p-cymene (14.58), respectively. Under the high ambient temperatures dietary oregano oil, Vitamin C, rosemary oil and an equal mixture of Vitamin C + E added to the basal basal diet were significantly (P≤0.05) increased the percentage of egg production and egg mass of Mandara layers. However, rosemary oil and an equal mixture of Vitamin C + E added to the diet were significantly (P≤0.05) heavier of egg weight than non-supplemented groups during the whole experimental period. Combinations of rosemary and oregano oils, combination of Vitamin C and E, rosemary oil, oregano oil, Vitamin C, Vitamin E alone in the diet treated groups were significantly (P≤0.05) enhancement of fertile eggs (%), hatchability/total eggs (%), sperm motility and sperm-cell concentration (X 109/ml) and decreased yolk cholesterol, serum
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cholesterol and glucose concentration, dead spermatozoa (%), sperm abnormalities (%) and acrosomal damage than in those controls treated group. Vitamin C addition alone or their combination with Vitamin E were significantly (P≤0.05) decreased body temperature and respiration rate of Mandara layers under Egyptian hot summer conditions. Blood pH was significant (P<0.05) decreased for layers fed Vitamin C, Vitamin E alone or their combination treated groups than in those controls. On the other hand, during the days post immunization control group created the lowest antibody levels, whereas individual antioxidant dietary supplementation alone or their mixtures had higher Sheep red blood cells (SRBC's) antibody levels when contrasted with the control group. However, blood serum activities of aspartate-aminotransferase (AST), alanine-aminotransferase (ALT) and malondialdehde (MDA) concentrations were significantly (P≤ 0.01) decreased, while total antioxidant capacity (TAOC) was significantly (P≤ 0.01) increased in all treated groups as compared with the control treated group. In conclusion, Vitamins C, E, rosemary oil, oregano oil alone or their combination showed better reduced the negative effects of heat stress and beneficial effect on maintaining immunity and antioxidant status under summer conditions.