Ingredient content and proximate composition of experimental diets.

*Vitamin and mineral mix (values are g kg− 1 except those in parenthesis): Premix: 25; Choline, 10; DL-a-tocopherol, 5; ascorbic acid, 5; (PO4)2Ca3, 5. Premix composition: retinol acetate, 1 000 000 IU kg− 1; calcipherol, 500 IU kg− 1; DL-a-tocopherol, 10; menadione sodium bisulphite, 0.8; thiamine hydrochloride, 2.3; riboflavin, 2.3; pyridoxine hydrochloride, 15; cyanocobalamine, 25; nicotinamide, 15; pantothenic acid, 6; folic acid, 0.65; biotin, 0.07; ascorbic acid, 75; inositol, 15; betaine, 100; polypeptides 12. **Nitrogen free extract (NFE, %) = 100—%CP—%CL—%Fibre Ingredient content and proximate composition of experimental diets.