The current work was conducted to reduce the negative effects of increasing stocking density by adding licorice powder to laying hen diets. Also, evaluate the impact of these treatments on productive and physiological performance of Inshas laying hens. A 3x3 factorial design experiment was performed including three stocking densities (6, 9 or 12 birds/m²) with three dietary levels of licorice (0, 0.5 and 1.0 %). A total number of 216 hens of Inshas local strain at 44 weeks of age were randomly distributed into 9 treatment groups with two replicates and housed during the experimental period 44 -56 weeks of age in floor pens with dimensions of 2 × 2 m. The results indicated that increasing stock density to 12 birds/m² caused a significant reduction in most of productive performance, fertility and hatchability percentages and blood parameters. Meanwhile, reducing stock density to 6 and 9 birds /m² participated in avoiding the negative effect. However, the best results for the previous parameters were exhibited by stocking density at 9 birds / m².
Regardless stock density, addition of licorice significantly increased egg production, egg number, egg weight, egg mass and improved feed conversion but feed consumption was not affected. Also, there was significant improvement in fertility and hatchability percentages, egg quality traits (egg shell thickness, Haugh unit score and egg yolk color) and most of blood parameters due to licorice supplementation. The best results were obtained by adding licorice at level of 0.5 %.
With regard to the interaction between stock density and licorice addition. It could be observed that, the highest egg production, egg weight, economic efficiency, the best feed conversion and the lowest feed consumption were recorded for hens received 0.5% licorice in their diet with stocking density of 9 birds / m². In addition, the best blood parameter values and the lowest plasma total lipids and LDL concentrations were achieved by the same treatment (0.5% licorice with stocking density of 9 birds/m²).
In conclusion, from this study, it can be concluded that adding 0.5% licorice to laying hen diets with stocking density to 9 birds /m² was more efficient in improving the performance and economic efficiency increasing of Inshas laying hens.