Effect of different sources and levels of zinc on egg quality and laying hen performance

Eighty layer hens were assigned in a completely randomized design to four dietary treatments containing zinc sulphate or organic zinc as Albino-Zn in two levels of 25 or 50 ppm. Feed intake was expressed on a per hen basis. Daily egg collection was expressed on a hen-day basis. Eggs were weighed to calculate egg mass. Feed conversion ratio was calculated as feed consumed per egg mass. Also all eggs produced on days 14, 28 and 42 were collected and used for egg quality parameters. Albumen height was measured and HU was calculated. The yolk and dried shell were weighed then albumen weight was calculated. There was no effect of zinc source or zinc level on egg production, egg weight or feed conversion ratio. However, feed intake was lower in the group receiving 50 mg kg(-1) organic zinc. There were no significant treatment differences for weight of egg components or shell thickness, but albumen height and HU were higher in the second fortnight for the groups receiving organic zinc at 25 or 50 mg kg(-1) than in the un-supplemented group.