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1. Light hybrid pullets kept in floor pens or in cages received one of five dietary treatments: a conventional developer diet (controls) or whole wheat unsupplemented (B) or supplemented with minerals (C), minerals and vitamins (D), or minerals and B vitamins only (E). The control diet was fed from 8 to 20 weeks and other diets from either 8 or 12 to 20 weeks of age. All groups received the same layers’ diet from 20 to 68 weeks of age.
2. Controls grew best and matured first: maturation was delayed by about 2.lb5 d with each 100 g reduction in body weight at 20 weeks. Body weights at 20 weeks, taking controls as 100, were 50, 70, 78 and 73 for B, C, D and E applied from 8 weeks and 72, 87, 87 and 86 when applied from 12 weeks. Lower‐leg length was increased by mineral but not by vitamin supplementation. Birds in floor pens grew faster than those in cages.
3. Mortality was nearly 30% in pullets receiving diet B from 8 to 20 weeks of age: feeding the diet from 12 weeks, or supplementing it with minerals (C), reduced mortality to 4% or less, but vitamins had no beneficial effect.
4. Conventionally fed birds laid more eggs than other groups.