Ingredients and analyzed chemical composition of diets.

1Corn starch in the basal diet was partially replaced with analytical grade zinc oxide (Sigma Aldrich, Taufkirchen, Germany) to adjust for the zinc concentration.2Mineral and Vitamin Premix (SpezialfutterNeuruppin Ltd., Neuruppin, Germany), providing per kg feed: 1.95 g Na (sodium chloride), 0.83 g Mg (magnesium oxide), 10,500 IU vitamin A, 1,800 IU vitamin D3, 120 mg vitamin E, 4.5 mg Vitamin K3, 3.75 mg thiamine, 3.75 mg riboflavin, 6.0 mg pyridoxine, 30 µg cobalamine, 37.5 mg nicotinic acid, 1.5 mg folic acid, 375 µg biotin, 15 mg pantothenic acid, 1,200 mg choline chloride, 75 mg Fe (iron-(II)-carbonate), 15 mg Cu (copper-(II)-sulfate), 90 mg Mn (manganese-(II)-oxide), 675 µg I (calcium-iodate), 525 µg Se (sodium-selenite).3Analyzed concentration of zinc in the basal diet without ZnO supplementation. The diets as fed contained 57, 164, and 2425 mg zinc/kg, adjusted by zinc oxide.