Effect of organic and mineral zinc and butyric acid on performance and egg shell quality traits in different breeding periods

The present study was carried out to investigatethe effects of different forms of zinc (no zinc, ZnO  and Zn-Met) and butyric acid on internal eggquality traits and performance in Hy-Line W36 strain laying hens using 144chickens from 74 to 83 weeks of age in the second phase of laying. A completerandomized block design with 3 × 2 factorial arrangement with six treatments, sixreplicates and four layers per replicate for nine weeks was used. Performanceparameters were measured daily and quality traits were measured in threeperiods of age. The results of the experiment showed that the main effects oforganic acid and three forms of zinc on egg production, defective eggs, eggweight, egg mass, feed conversion ratio and daily feed intake were notsignificant during the whole experiment. During the period of 74 to 77 weeks,feed conversion ratio for the treatment containing mineral zinc and organicacid was higher than other treatments (P