Effect of Probiotic, Thyme, Garlic and Caraway Herbal Extracts on the Quality and Quantity of Eggs, Blood Parameters, Intestinal Bacterial Population and Histomorphology in Laying Hens

In the current Iranian poultry industry, antibiotics are the most frequently used additive in feeds to increase the productivity. Regarding the negative effects on human health due to consuming chicken whose feeds contain antibiotics, finding an appropriate alternative is of a great importance. This study aims to find an appropriate and harmless feed additive to increase the quality and quantity of poultry eggs. Total of 60 laying hens which had been in production for 85 weeks were allocated in a completely randomized design considering five treatments with four replicates and three birds in each. Group one received a layer basal diet with no supplementation which served as control. The second, third and fourth groups received basal diet with 1 mL of herbal extracts (garlic, thyme and caraway) / L drinking water, respectively. The fifth group fed the basal diet plus 1 g of probiotic / kg diet. The number and weight of produced eggs were measured in a daily manner, feed consumption in weekly manner and the egg quality, yolk cholesterol, intestinal bacterial population and effect of treatments on the morphology of the small intestine were measured at the end of experiment after 8 weeks. All treatments showed no overall effect on quality and quantity of produced eggs in comparison with controls; however, the thyme and garlic extracts reduced the cholesterol of serum and yolk relative to the control. The herbal extracts caused a significant decrease in the intestinal bacterial population and probiotic increased villus height in ileum (P < 0.05).