Animal Nutrition and Feed Technology

Heat stress is a demanding issue that results in substantial economic losses for the hens’ husbandry industry. A 8-wk feeding trial was conducted to evaluate the dietary herbal extract mixture (Scutellaria baicalensis and Lonicera japonica, HEM) supplementation as a means of ameliorative strategy against the adverse effects of seasonal heat stress on performance of laying hens. In total, 288 ISA Brown 25wk-old layers were divided into three treatments: CON, basal diet; T1, basal diet with 0.025% HEM; T2, basal diet with 0.05% HEM. There were no differences (P>0.05) in egg production and nutrient digestibility among treatments throughout the experimental period. The HEM supplementation increased (P<0.05) eggshell thickness and eggshell strength during 4th and 8th wk, respectively. Compared with CON, yolk height was increased (P<0.01) in response to HEM treatments during the 8th wk. The Haugh unit was improved (P<0.01) by the addition of HEM in 4th wk and 8th wk. Additionally, there was a significant reduction (P<0.05) in serum cortisol concentration upon dietary supplementation of 0.05% HEM. In conclusion, precised HEM supplementation could improve eggshell strength and shelf life in laying hens when reared under hot climatic conditions.