Oxidative stability of chilled broiler breast meat as affected by dietary supplementation with rosemary (Rosmarinus officinalis L.) powder and vitamin E

Abstract The aim of the present study was to evaluate the effect of rosemary (Rosmarinus officinalis L.) powder and vitamin E, as feed additives combined at different levels, on oxidative stability of broiler meat up to 14th day after chilling. A total of 270 1‐day‐old male chicks of Ross 308 strain were randomly assigned to nine dietary groups with three replicates having 10 birds each. Diets were supplemented with 0, 0.5, or 1.0% of rosemary (R) powder and 0, 100, or 200 mg/kg of vitamin E (alpha‐tocopherol acetate; VitE) according to the following treatments: T1 – control basal diet (0R + 0VitE); T2 – 0R + 100VitE; T3 – 0R + 200VitE; T4 – 0.5R + 0VitE; T5 – 0.5R + 100VitE; T6 – 0.5R + 200VitE; T7 – 1.0R + 0VitE; T8 – 1.0R + 100VitE; and T9 – 1.0R + 200VitE. At day 42, two birds of each replicate were slaughtered and the length and weight of cecum was recorded. Carcasses and their economically valuable parts were also weighted and broiler breast refrigerated at 4°C for 14 days. At day 0, 4, 7, and 14 of storage the malondialdehyde (MDA) content of breast meat was evaluated. After 4 days of storage, meat MDA contents of the T5 (0.43 mg/kg) and T9 (0.41 mg/kg) were lower than control group (T1: 0.55 mg/kg; p < .05). On day 7, groups supplemented with rosemary or VitE alone showed similar MDA contents (p > .05) than control. On day 14, lower (p < .05) MDA contents than T1 were observed in all groups except for broilers fed diet supplemented only with vitamin E. No effects were observed between treatments on the relative weight of the several carcass traits, however, VitE influenced (p < .05) the weight and size of cecum. Based on our findings, the combination of rosemary powder and vitamin E at different levels in diet is useful to limit the lipid oxidation of chilled chicken meat.


| Study design and diet composition
The experimental design included nine treatments with three replicates for each dietary treatment. Each replicate had 10 birds, such that mean body weights were similar between groups. All chickens were fed according to the producer's feeding instructions. The composition of basal diet and its nutrient composition in the starter (1-21 days of age) and finisher (22-42 days of age) rearing periods are given in Table 1.
T A B L E 1 Ingredient and chemical composition of the basal diet fed to broiler chickens

| Meat oxidation evaluation
The Thiobarbituric acid (TBA) was determined based on the description of Tarladgis, Watts, and Yonathan (1960). This tissue TBA assay is considered as a standard method for malondialdehyde (MDA) analysis (Tokur, Korkmaz, & Ayas, 2006) and involved the reaction between two molecules TBA and one molecule MDA. Each homogenized sample was added to 97.5 ml of distilled water and 2.5 ml of 6 N HCl and distilled until reaching 200 ml of distillate. A total of 5 ml of thiobarbituric reactive reagent (0.02 M TBA in 90% glacial acetic acid) was added in equal part to 5 ml of distillate. This mixture was incubated for 35 min on boiling water. After cooling, the absorbance was measured at 538 nm. The multiplication by 7.8 was used in order to calculate the distillation TBA number as described by Tarladgis et al. (1960).

| Statistical analysis
The following formula: [(weight of component(s)/eviscerated carcass weight) × 100] was used for respective ratios calculation. Data were tested by analysis of variance using a 3 × 3 factorial design with three rosemary (0, 0.5, and 1.0%) and three vitamin E (0, 100, and 20 mg/kg in diet) levels, using the two-way ANOVA procedure. Data were analyzed using SPSS (1997) statistical software and the GLM procedure was used. The means (±SEM) were compared by using least significant difference (LSD). Results were considered significantly different at p < .05.

| RESULTS
A significant effect (p < .05) of both rosemary powder and vitamin E dietary supplementation on MDA contents of breast meat broiler was observed on 4th, 7th, and 14th day after chilled storage ( Rosemary powder influenced (p < .05) the weight and relative weight of the right cecum. An effect of vitamin E was observed on length of right and left cecum (p < .05; Table 3). However, no significant differences (p > .05) were found between dietary groups for the right cecum width (8.09 mm) and diameter (0.36 mm). The left cecum weigh, relative weight, width, and diameter were as follows: 6.77 g, 0.28%, 8.36 mm, and 0.36 mm, respectively, without significant differences (p > .05) between groups.
No significant differences (p > .05) among treatments on broilers' live body weight and empty abdomen carcass weight as well as eviscerated carcass percentage (Table 4) or on breast and drumsticks relative weight were observed (Table 5).

| DISCUSSION
Thiobarbituric acid (TBA) analysis is an indicator of malondialdehyde (MDA), a product of oxidation that increases during the storage period (Yesilbag et al., 2011). The results of our study showed that the rosemary supplementation in broiler diet combined with vitamin E, but not as single additive, was effective in order to prevent the breast  In the present study, the weight and relative weight of carcass and several carcass parts were similar among treatments, suggesting that the 0.5 and 1.0% of rosemary supplementation with or without vitamin E have no adverse effect on carcass biometric characteristics.
However, the increment of weight and relative weight of right cecum, when 0.5% rosemary powder was added or the small length of cecum when 200 mg/kg vitamin E was added, suggested a real influence of both additive in the organ development of broilers. In fact, the feeding rosemary can improve the body weight gain, but not the final live weight of broilers, as reported by Yesilbag et al. (2011). However, Basmacioğlu et al. (2004) observed a decrease in weight gain at the end of the starter feed period (21st day) in broilers fed diet including rosemary. This increment was not always evident, and Yesilbag et al.
(2011) also observed no significant differences with rosemary supplementation on broilers live weight gain.
In conclusion, supplementing rosemary and vitamin E in diet at 0.5% + 100 mg/kg and 1.0% + 200 mg/kg, respectively, reduced significantly the lipid oxidation of chilled chicken meat at 4th, 7th, and 14th day without any adverse effect on the carcass parts and meat cuts.

ACKNOWLEDGMENT
This work was supported by Rasht Branch, Islamic Azad University (grant number 4.5830).