Abstract

This experiment was conducted to determine the effects of diets with three different levels of calcium (% 0.8, 1.6, 3.2) and four different levels of boron (0, 75, 150, 300 mg kg-1) in prelaying period (14-20 weeks) on growth, bone ash and subsequent performance and egg shell quality of laying hens. A total 864 Super Nick pullets at 14 weeks of age were randomly allocated to twelve treatments arranged in a 3x4 factorial design with six replicates of 12 pullets each. Feed and water provided for ad-libitum access. The tibia samples were taken, three pullets and hens from every replicates at 20 and 42 weeks of age, respectively. Results of the present experiment showed that body weights and body weight gains were reduced in high prelay dietary Ca and B as the main factor. Feed intake of the pullets was not significantly influenced by the treatments. There were no detectable difference in feed intake, egg production, egg mass and feed conversion ratio (g, feed/ g, egg mass) and eggshell weight, but interactive effects of dietary Ca and B levels on eggshell thickness, egg specific gravity and shell breaking strength was significant. Shell thickness and breaking strength were significantly higher in hens fed pre-lay diet with 3.2 % Ca and no supplemental B than other treatments and egg specific gravity was significantly reduced by feeding 1.6 % Ca and 75 mg kg-1 B at 36 weeks of age. Bone ash (g or %) of hens at 20 and 42 weeks of age was not changed by Ca levels or interaction dietary Ca and B levels, but pullets receiving the 150 mg kg-1 B as the main factor had significantly higher in bone ash (g or %) values than other dietary B levels.