The Effects of Probiotic and Thyme Powder on Growth Performance, Carcass Traits and Blood Biochemical Parameters of Broilers with Normal and Crude Protein Reduced Diets

Extentet Abstract Introduction and Objective: Substances of microbial origin and medicinal plants, by improving the level of health and condition of the gastrointestinal tract, provide the basis for the optimal use of nutrients in diets, and by reducing the use of nutrients, while saving production, also prevent environmental pollution. Dietary protein sources are among the most expensive nutrients, reducing their use in poultry diets not only reduces the cost of nutrition, but also prevents environmental pollution by reducing the excretion of nutrients through animal feces. The present experiment was performed to investigate the possibility of reducing the level of crude protein in broiler diets using two probiotic additives and thyme. This experiment was conducted to investigate the effects of adding probiotc and thyme medicinal plant into normal and 5% lower level crude protein on growth performance, carcass traits and blood biochemical parameters of broilers. Matterial and Methods: In this experiment 192 Ross 308 broiler chicks were used in 2×2 factorial arrangements with 4 treatments, 4 replicates and 12 chicks in each replicate in a completely randomized design in grower (11 to 24 days) and finisher (25 to 42 days) periods. Results: In grower period adding probiotic in contrast with thyme significantly increased the amount of daily weight gain (p<0.05). In finisher and total periods, feed additives and diets crude protein level had no effect on performance of broilers. Using probiotic in low crude protein diets redced the carcass percentage of broilers (p<0.05). The level of 5% of crude protein reducing decreased the concentration of blood triglyceride and increased the blood concentration of LDL as compared with normal level of diet crude protein (p<0.05). Thyme powder in low crude protein diets decreased the amount of blood triglyceride (p<0.05). Thyme powder with low crude protein diets increased the amount of blood LDL whereas with normal crude protein diets the level of LDL was decreaased (p<0.05). Conclusion: Generaly, in broilers reducing 5% of diets crude protein had no adverse effects on their performance and also using microbial and herbal feed additives had no significant effect  on broiler performance.