Effects of phytogenic feed additive based on thymol, carvacrol and cinnamic aldehyde on body weight, blood parameters...

The aim of this study was to evaluate whether a phytogenic feed additive (PFA) based on essential oils such as carvacrol, thymol and cinnamic aldehyde, could be considered a replacement for antimicrobials used as growth promoters in broiler chickens, as well as to investigate its effect on total bacterial count, biochemical profiles, meat quality and meat fatty acid profile. A total of 240 broiler chicks were randomly distributed into 4 groups with 4 replicates of 15 animals each, as follow: T1 (basal diet only; the control group), T2 (basal diet supplemented with zinc bacitracin), T3 (basal diet with 0.5% of the PFA), T4 (basal diet with 1.0% of the PFA). The addition of 0.5% of the PFA improved live body weight of supplemented birds compared to the control group at 35 and 42 days of age, while the total bacterial count in the environment was reduced when 1.0% of the PFA was used. In addition, intestinal villi height and crypt depth suffered variations during the entire experiment in birds treated with both concentrations of the PFA and zinc bacitracin. Total erythrocyte counts were higher on days 14, 28 and 42 in both treated groups (PFA) compared to the control group, as well as hemoglobin content on days 28 and 42. On the other hand, leukocyte counts were lower on days 14, 28 and 42 due to reduced lymphocyte counts in both PFA treated groups compared to the control group. Serum levels of alanine aminotransferase (ALT) were lower in broilers fed with either concentration of PFA on day 14 of life, and the same was observed regarding aspartate aminotransferase (AST) in broiler treated with 0.5% of the PFA. Also, total protein and globulin levels were lower on days 14 and 28 in groups fed with phytogenic compared to the control group. Regarding meat quality, breast meat showed higher red intensity and shear force in groups fed with both concentrations of phytogenic compared to the control group, while weight loss by cooking was lower. Finally, 1.0% of phytogenic showed lower docosadienoic acid (C22:2) content in breast meat. In conclusion, results showed that the use of PFAs based on carvacrol and thymol may be considered an interesting alternative to increase broilers performance, replacing the use of antimicrobials as growth promoters, as well as an interesting alternative to reduce the total bacterial count in the environment of broiler chickens. Moreover, the diet containing phytogenic also showed hepaprotective effects but deserves attention regarding possible alterations on the immune response.