Impacts of dietary different levels of thyme leave powder as a natural growth promoter on growth performance, carcass characteristics, and blood indices of broilers

The objective of the present study was to ascertain the influence of thyme leaf powder (TLP) on growth rate, carcass features, and blood indicators in broiler diets as a natural antioxidant and antibiotic substitute. A fully randomized design experiment divided 264-day-old broiler chicks (Ross 308) into 4 experimental groups. Six replicates of each group, each containing 11 unsexed chicks, were created. The following were the therapies: control group without additive (basal diet); TLP1, TLP2 and TLP3: basal diet + 1, 2 and 3 g thyme leaves powder/kg diet, respectively. Results showed that TLP added at 2 or 3 g/kg of feed significantly enhanced body weight gain (except for the period from 16 to 30 d of life), feed intake (except for the period from 1 to 15 d of life), and feed conversion ratio throughout study period. Furthermore, there was a significant decrease in creatinine and alanine aminotransferase (ALT) with different TLP levels, particularly at a 3 g TLP/kg diet. Compared with the control group, the birds' 2 g TLP/kg diet included the highest levels of albumin and total protein and A/G (albumin/globulin) ratio. Furthermore, the birds fed 1 g TLP/kg feed had the lowest concentrations of low-density lipoprotein (LDL) and total cholesterol (TC). Moreover, chicks fed all treatment diets containing TLP had higher IgY concentrations than the control group. Nevertheless, the group that was fed a diet including 2 g TLP/kg had the highest IgM levels. Additionally, the superoxide dismutase activity (SOD) levels were highest in the birds fed a 1g TLP/kg diet and minimum in the birds fed the control diet. Notably, malondialdehyde (MDA) levels were maximum in birds fed a control meal and lowest in birds with a diet containing 1 g of TLP/kg. We may conclude that using TLP in broiler diets increases the birds' immunity, productivity, and overall health, especially at level 2 g of TLP/kg diet.