This study aimed to determine the effects of vitamin C and propolis-supplemented feeds on some blood parameters, lipid peroxidation, and activities of some antioxidant enzymes in broilers exposed to oxidative stress. 360 three-day-old broiler chicks (Ross 308) were randomly divided into four treatment groups each containing 90 animals, including six replicate groups for each treatment. The experimental groups were designated for a 3-42 days period as follows: no supplement to basal ration (Control-Group I); supplement of 500 ppm vitamin C and 200 ppm lead (as lead acetate) to basal ration (Group II); supplement of 1 g/kg propolis and 200 ppm lead (as lead acetate) to basal ration (Group III); and supplement of 200 ppm lead (as lead acetate) to basal ration (Group IV). The highest TG level (86.83 mg/dl) was observed in the lead supplemented group; however, the lowest aspartate aminotransferase (SGOT) level (90.71 IU/L) was observed in the control group (p<0.05). The addition of lead increased the plasma malondialdehyde (MDA) level (p<0.01) compared to other treatments. However, the addition of vitamin C and propolis decreased the plasma MDA level close to control levels. The highest erythrocyte superoxide dismutase (SOD) activity was observed in the lead addition group (p<0.01) while no significant differences were observed for SOD activities of the control, vitamin C +lead, and propolis+lead groups. The plasma reduced glutathione (GSH) activity of the control (2.30 μmol/ml) was significantly lower than the lead administered group (6.20 μmol/ml) (p<0.01); while this parameter was determined to be similar to other groups. No significant differences were observed between groups for liver GSH activity, but heart GSH activity of the control was significantly higher in comparison to other treatments (p<0.05). To obtain similar antioxidant effects, it is recommend that using propolis (1 g/kg) and vitamin C (500 mg/kg) supplementation in broiler diets may overcome the adverse effects of oxidative stress originating from dietary lead.

In this study, the effects of propolis and vitamin C (L-ascorbic acid) supplementation in diets were investigated on feed intake (FI), body weight (BW), body weight gain (BWG), feed conversion rate (FCR) and digestibility and on egg production and qualities (weight, mortality, shell thickness) in laying hens exposed to heat stress. A total of 150 Hyline White Leghorn, aged 42 weeks, hens was divided into five groups of 30 hens. Chicks were randomly divided into 1 positive control, 1 control and 3 treatment groups. The chicks were kept in cages in temperature-controlled rooms at 22°C for 24 h/d (positive control, Thermoneutral, TN group) or 34°C for 9 h/d from 08.00-17.00 h followed by 22°C for 15 h (control, heat stress, HS group) and fed a basal diet or basal diet supplemented with vitamin C (250 mg/kg of L-ascorbic acid/kg of diet) or two levels of propolis (2 and 5 g of ethanol extracted propolis/kg of diet). Increased FI (p<0.05) and improvement in FCR (p<0.05), hen day egg (p<0.05) and egg weight (p<0.05) were found in Vitamin C and propolis-supplemented laying hens reared under heat stress conditions. Mortality rate was higher in the control group than TN, vitamin C and propolis groups (p<0.05). Digestibility of dry matter, organic matter, crude protein and ether extract improved with increasing of both dietary vitamin C and propolis (p<0.05). Vitamin C or propolis supplementation did not affect either the percentage shape index, yolk index or haugh unit and albumen index (p>0.05). However, the egg shell thickness and egg shell weight appeared to be increased in Vitamin C and propolis groups in comparison to HS group birds (p<0.05). In conclusion, dietary supplementation of laying hens with anti-oxidants (vitamin C and propolis) can attenuate heat stress-induced oxidative damage. These positive effects were evidenced by increased growth performance and digestibility, improvement of egg shell thickness and egg weight in comparison to non-supplemented birds. Moreover, supplementation with propolis (5 g/kg diet) was the most efficient treatment.

In this study, we investigated the antioxidant activity of ethanol extracts of propolis (EEP) and vitamin C on biochemical indicators and antioxidant enzyme activities of broilers exposed to heat stress (at 34 °C). The experimental groups were as follows: group I (positive control) and group II (control) were fed a basal diet, group III (vitamin C) was fed a basal diet supplemented with 250 mg vitamin C as ascorbic acid/kg, group IV (EEP-0.5) was fed a basal diet supplemented with 0.5 g EEP/kg, group V (EEP-1) was fed a basal diet supplemented with 1 g EEP/kg, group VI (EEP-3) was fed a basal diet supplemented with 3 g EEP/kg. Plasma superoxide dismutase levels of positive control, control, vitamin C, EEP-0.5, EEP-1 and EEP-3 groups were found as 0.34, 1.23, 0.50, 0.90, 0.30 and 0.41 μkat/ml, respectively (p < 0.01). Aspartate transaminase (except for EEP-0.5 and EEP-1 groups) and alkaline phosphatase in the control group were significantly higher than those of positive control, vitamin-C and EEP-3 groups. Malondialdehyde level in plasma, liver and muscle tissues of control group were found significantly (p < 0.05) higher than those of positive control and EEP-3 groups. Catalase activities of blood, liver, kidney and heart were the highest in the control group. Reduced glutathione activities of plasma and liver of all groups were not significantly different from each other, whereas those of muscle, kidney and heart were significantly higher in the control group. Significantly lower levels of glutathione peroxidase were found in blood, liver and kidney tissues of the control group (p < 0.05), whereas those of muscle and heart were similar in all groups. The results of the present study suggest that EEP and specially EEP at the supplemented dose of 3 mg/kg diet might be considered to prevent oxidative stress in the broilers exposed to heat stress.

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