LAUSR

An experiment was conducted to investigate the effect of dietary calcium (Ca) level on growth performance and bone characteristics to evaluate the Ca requirements for Sheldrake ducklings from 1 to 21 days of age. A total of 1080 day-old male Campbell Sheldrake ducklings were randomly allotted to one of six treatments with six replicate cages of 30 birds per cage with a completely randomised design. A basal diet with 0.40% non-phytate phosphorus was supplemented with Ca source (calcium carbonate) to achieve graded concentrations of Ca (0.45–1.20%) in diets with an increment of 0.15%. The bodyweight, average daily gain and average daily feed intake displayed quadratic responses to increasing concentrations of dietary Ca with maximal responses for ducklings fed the diets with 0.60 and 0.75% Ca. Serum Ca concentration, tibia ash percentage, Ca content in tibia ash and bone mineral density were increased linearly (P < 0.02) as dietary Ca concentrations increased. According to the non-linear regression analyses, the Ca requirements for maximal weight gain and bone mineralisation of Sheldrake ducklings from 1 to 21 days of age were estimated at 0.60% and 0.64–0.87% respectively.