The effect of two organic and inorganic forms of zinc on yield, egg quality traits, antioxidant activity and bone strength in older laying hens

The aim of this study was to investigate the effect of two mineral and organic forms of zinc on antioxidant activity and bone strength in the last phase of laying hens. 175 Leghorn laying hens (w36) with 80 week of age were divided into 7 treatments and 5 replications in a completely randomized design. The treatments were: control (without zinc supplementation) treatments containing zinc sulfate (15, 30 and 45 mg/kg). Organic zinc treatments (15, 30 and 45 mg/kg, respectively). The results showed that there was a significant increase in feed intake between the control treatment and 15 and 45 mg inorganic zinc and all organic zinc treatments (P<0.05). Egg weight in 45 mg inorganic zinc and all organic zinc treatments and egg mass in 15 and 30 mg organic zinc treatments showed a statistically significant increased. feed conversion ratio of organic zinc treatments was decreased significantly (P<0.05) . Regarding to egg quality traits, no significant difference was observed between experimental treats with control treatment (P>0.05). Both mineral and organic zinc supplements increased serum SOD activity as an antioxidant index at all levels (P<0.05). Tibial bone strength increased in laying hens of receiving 30 mg/kg organic zinc. According to the results, organic zinc can be improved feed intake and feed conversion ratio; Increased yield, antioxidant activity and bone strength in laying hens in the final stages of production.