effect of thyme, garlic and caraway herbal extracts on blood parameters, productivity, egg quality, hatchability and intestinal bacterial population of laying japanese quail

background: in the current iranian poultry industry, antibiotics are the most frequently used additive in poultry feeds to increase productivity. the negative effects on human health, resulting from the consumption of chicken whose feeds contain antibiotics, makes finding an appropriate alternative of great importance. as a result of their nature, herbal extracts could be specifically considered for this purpose. objectives: this study aimed to find an appropriate and harmless feed additive to increase the quality and quantity of poultry eggs. methods: a completely randomized design including 4 treatments, 4 replications and 4 birds in each experimental unit was applied. herbal extracts were added to drinking water of treatments in ratio of 1:1000, with the control group containing no additives in their water. the number and weight of produced eggs were measured on a daily basis, feed consumption on weekly basis and the egg quality, yolk cholesterol, hatchability and intestinal bacterial population were measured at the end of experiment after 8 weeks. results: herbal extract treatments showed no overall effect on quality and quantity of produced eggs in comparison with control; however, the thyme and garlic extracts reduced the cholesterol of serum and yolk relative to the control. herbal extracts did not significantly affect the hatchability of fertile eggs. the herbal extracts caused a significant decrease in the intestinal bacterial population of laying quails. conclusions: the garlic extract had the most decreasing effect on the cholesterol of serum and egg yolk. furthermore, thyme extract had the most decreasing effect on the intestinal bacterial population.