Influence of Added Manganese, Magnesium, Zinc, and Calcium Level on Egg Shell Quality

Three experiments were conducted to study the effects of dietary calcium level on the addition of manganese, magnesium, or zinc on the performance of Leghorn hens. In the first experiment, manganese, magnesium, or zinc was added to diets containing either 2.5 or 3.5% calcium and fed for 12 periods of 28 days. The highest calcium level significantly improved specific gravity and numerically improved hen-day production, feed conversion, and shell thickness. Calcium level also had a significant effect on magnesium, manganese and zinc content of the shells. The addition of manganese improved shell thickness, especially when compared to the addition of magnesium or zinc. In Experiment 2, zinc was added to a 3.6% calcium diet at levels of 0,200, or 400 mg/kg. These levels had no significant effect on any parameters studied. Forced molted hens in Experiment 3 were fed a 3.6% calcium diet to which was added either 1% calcium (as oyster shell), 180 mg manganese/kg, or both. The additions of the calcium significantly improved shell thickness and specific gravity.