Evaluation of Performance and Qualitative Traits in the Aged Laying Hens using the Inhibitor of Beta Adrenergic Receptors

The design of this study was done to investigate the effects of inhibiting the activity of beta-adrenergic receptors by supplementation of different concentrations of propranolol (as a none-selective inhibitor of beta- adrenergic receptors) on some of the performance characteristics in laying hens at the end of the economic production period and the qualitative traits of eggs. The experiment was performed in a complete randomized design, over a 26-day period, using 64 laying hens (90 weeks’ age) included 4 treatments (including control treatment and propranolol treatment with concentrations of 1, 2, and 3 mg Per kilogram of live body weight) with 4 repetitions and each repetition consisted of 4 birds, and some of the performance characteristics, follicular size (F1-F5) and egg quality were measured and calculated. The data obtained from the performance characteristics show that the usage of all concentrations of this inhibitor causes the significant increase in the laying percentage, improvement of feed conversion ratio. Propranolol also significantly increased feed intake and F1 follicle size at a concentration of 3 mg. Regarding the qualitative parameters of eggs, the usage of this inhibitor causes the significant increase in the thickness of the egg shell, the significant increase in the shell weight and ratio of the shell to the total weight of the eggs and the improvement of the Hue index in concentrations of 2 and 3 mg propranolol in treated birds. Therefore, it can be concluded that supplementation of different concentrations of propranolol in this study has been capable of improving some of the performance and qualitative characteristics of eggs in laying hens at the end of the production period.