Table 1. Ingredients and chemical composition of diets used in this study.

Ingredients	g/kg	Chemical composition	g/kg
		Dry matter	885
Optigrain®1	500	ME(MJ/kg)	13.5
Barley	100	Crude ash	70
Wheat	70	Crude protein	189
Soybean meal	190	Crude fiber	29
Corn starch/zinc oxide2	10.0	Ether extract	39
Whey powder	60	Starch	386
Mineral & Vitamin Premix3	10	Lysine	11.8
Soy oil	20	Methionine	4.1
Monocalcium phosphate	16	Threonine	7.1
Limestone	18	Tryptophane	2.3
Salt	2.5	Calcium	11.1
Lysine HCl	2.5	Phosphorus	7.7
Methionine	1.0	Sodium	2.7
		Magnesium	1.8
		Zinc mg/kg4	50
		Iron mg/kg	119
		Manganese mg/kg	80
		Copper mg/kg	18

¹Optigrain® (DEUKA, Deutsche Tiernahrung, Düsseldorf, Germany), consisting of hydrothermally processed wheat (50%), barley (25%) and corn (25%).

²Corn starch in the basal diet was partially replaced in the diets containing 150, and 2500 mg/kg zinc with analytical grade zinc oxide (Sigma Aldrich, Deisenhofen, Germany) to adjust for the zinc level.

³Mineral and Vitamin Premix (Spezialfutter Neuruppin Ltd., Neuruppin, Germany), containing per kg dry matter: 130 g Na (as sodium chloride), 55 g Mg (as magnesium oxide), 700,000 IU Vit A, 120,000 IU Vit D3, 8,000 mg Vit E, 300 mg Vit K3, 250 mg Vit B1, 250 mg Vit B2, 400 mg Vit B6, 2,000 µg Vit B12, 2,500 nicotinic acid, 100 mg folic acid, 25,000 µg biotin, 1,000 mg pantothenic acid, 80,000 mg choline chloride, 5,000 mg Fe (as iron-(II)-carbonate), 1,000 mg Cu (as copper-(II)- sulfate), 6,000 mg Mn (as manganese-(II)-oxide), 45 mg J (as calcium-iodate), 35 mg Se (as sodium-selenite).

⁴Analyzed concentration of zinc in the basal diet without ZnO supplementation. The other diets contained 156, and 2355 mg/kg, respectively.