Physiologic assessment of the reproductive alterations during the first annual molting of commercial chicken (Gallus gallus domesticus, L.) layers

Three studies were conducted to assess the physiologic relations on the reproductive alterations during the first annual natural and induced molting of commercial layers. In study 1, the reproductive performance of molting layers at the different phases of feather shedding were evaluated by the change in body weight, feed conversion ratio, hen-day egg production, oviposition interval and mortality. Egg quality characteristics such as albumen, yolk, egg shell and air cell quality were assessed. Three layers of the same treatments were sacrificed to assess the morphologic (macroscopic and microscopic) changes in reproductive system as well as other structures in study 2 but prior to this, hematologic values and basic physiologic functions were evaluated. In study 3, post molt production performance of the recovered layers in study 1, was evaluated through hen-day egg production, egg mass, and egg quality characteristics of the albumen, yolk, shell and air cell. Data in study 1 and 2 were analyzed following a 4x2 factorial in completely randomized design (CRD) with the phases of feather shedding as factor 1 and molting methods as factor 2. In study 3, data were analyzed in CRD with the NAT (natural) and IND (induced) groups as treatments. An equally improved production performance was found using natural and induced molting method at the recovery phase. The induced layers showed a more intense reproductive tract and ovarian regression at the different phases of feather shedding but had an earlier reproductive rejuvenation compared with the natural molting layers although both were similarly redeveloped during recovery. The changes in hematologic values indicate a more stressful condition in the layers induced to molt. However, after the molt period, the production performances of the induced molting layers were found to be better than the natural molting layers giving a significantly higher egg production with thicker and heavier egg shell.