The objective of this study was to investigate the effects of thyme and oregano essential oils (as growth promotors), individually and in combination, on the health, growth performance, and prevalence of muscle abnormalities in broiler chickens. Six hundred day-old Cobb 500 hybrid chickens were randomized into four dietary treatment groups with three replicates each. Chicks in the control group (C) received a basal diet, while the experimental treatment groups received basal diets containing 350 mg/kg of thyme oil (T1), 350 mg/kg of oregano oil (T2), and 350 mg/kg of thyme and oregano oil (T3). Growth performance parameters were evaluated at 14, 28, and 42 days. The broilers in treatments T1 and T2 had significantly higher body weights than the control group. The feed conversion ratio was the lowest in chicks who received oregano oil, followed by those fed thyme oil. The overall prevalence of growth-related breast muscle abnormalities (including white striping and white striping combined with wooden breast) in groups receiving essential oils (T1, T2, and T3) was significantly higher than in the control group (C). The thyme and oregano oil diets showed no significant differences in antibody titers against Newcastle disease or interferon-γ (INF-γ) serum levels. In conclusion, thyme and oregano oils had a positive impact on the growth performance of broiler chickens but increased the incidence of growth-related breast muscle abnormalities.

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The aim of this study was to assess the occurrence of white striping (WS), wooden breast (WB), and WS combined with WS/WB muscle abnormalities in broilers (Ross 500) at different slaughter ages (34, 41, and 48 d). In addition, the influence of these muscle abnormalities at different slaughter ages on quality characteristics (physical dimensions, pH, color index, and chemical composition) was studied. Overall occurrence of muscle abnormalities was 45%, 92%, and 100% at slaughter ages of 34, 41, and 48 d, respectively. It was found that about 39% from the occurrence of muscle abnormalities was not similar in the same bird (left and right fillets). Breast fillets affected by muscle abnormalities had significantly (p<0.05) higher weight than normal fillets. At slaughter age of 34 d, normal fillets had significantly higher L* (67.37 vs. 61.73 and 63.05, p<0.05), lower a* (3.25 vs. 4.87 and 5.18, p<0.05) and b* (4.02 vs. 5.20 and 5.99, p<0.05) than WS and WS combined with WB fillets; respectively. The changes in chemical composition due to muscle abnormalities were more significant at high slaughter age than at low slaughter age. In conclusion, the occurrence of muscle abnormalities was strongly influenced by slaughter age. Moreover, breast fillets affected by muscle abnormalities had different quality characteristics (proximate composition, color traits, and dimensions) in comparison to normal fillets.

The objective of this study was to investigate the effect of dietary supplementation with black cumin seed meal (BCSM) and coconut meal (CM) on the performance and cecal microbiota of Cobb 500 hybrid broilers. The study was conducted on 600 chicks on the first day of hatching; the chicks were randomly distributed equally into 12 equal-sized floor pens. Four dietary treatments (C, T1, T2 and T3) were replicated three times (50 chicks/replicate): C was the control group; T1 was supplemented with 10% BCSM; T2 was supplemented with 10% CM; T3 was supplemented with 5% BCSM and 5% CM. At slaughter age on day 35, our findings showed that treatment T2 increased significantly body weight and feed conversion ratio (FCR) compared to C, T1 and T3. In addition, the hot carcass dressing percentages in treatments T1, T2, and T3 were significantly higher than that of the C group. The results of relative normalized comparative gene expression of Clostridioides difficile, Roseburia and Streptococcus were not significantly changed in all treatments (p > 0.05). Treatment T1 resulted in a significant decrease in gene expression of the entire microbiota, while treatment T2 resulted in a significant increase in gene expression of all microbes, leading to an enriched and diverse microbial community. It can be concluded that supplementation with 10% BCSM is beneficial in inhibiting pathogenic microbes during early post-hatch days. In contrast, CM may promote and enhance the diversity of microbial communities during broiler growth. The inclusion of non-conventional feed ingredients in poultry diets may improve growth performance and may reduce the cost of broiler feed.