A total of 1,120 14-week-old Jingfen-1 laying hens with similar performance

A total of 1,120 14-week-old Jingfen-1 laying hens with similar performance (body weight: 1,191.31 plus/minus 42.17 g; egg production rate: 16.09 plus/minus 5.70 %) were randomly divided to 4 treatments with 10 replicates of 28 birds. The trial lasted 14 weeks included a 2-wk acclimation period and a 12-wk experimental period and the experiment was conducted in Jingzhou Haida Layers Demonstration Farm (Jingzhou, China).Laying hens in the control group were fed a basal diet, and the three experimental groups were fed the basal diet supplemented with 250, 500, and 1,000 mg kg-1 GCM (powder, 80 % GML, 5.4 % cinnamaldehyde, and 0.6 % thymol, CALID BIOTECH (WUHAN) CO., LTD., Wuhan), respectively, according to the studies (Zhao et al. 2019; Cui et al. 2023).The corn-soybean meal-based diet (Table 1) was formulated to meet or exceed the nutrient requirements of NRC (1994). The temperature and relative humidity in house were 25 plus/minus 2 degrees Celsius and 60 to 70 %, respectively, with a 16:8 L:D light program used during the trial period (Liu et al. 2023). An enclosed, ventilated, and conventional house was provided for all laying hens to keep them in the same environmental conditions. Feed and water were offered ad libitum.