Comparison between concentrated complete diets and self‐selection for feeding sexually‐maturing pullets at hot and cold temperatures

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Abstract
1. Pullets in late growth and early lay were maintained at hot (25° to 35°C) or cold (6° to 16°C) ambient temperatures and either fed complete diets or allowed to self‐select nutrients from separate energy‐ and protein‐rich foods. 2. Manipulating the metabolisable energy (ME) and/or nutrient density (ND) of complete layer diets failed to improve egg output at hot temperatures to that obtained at cold temperatures. 3. At both temperatures self‐selection increased protein, but not ME, intake. This increased egg output and body weight gain at the hot, but not cold, temperatures. At the hot temperatures pullets fed by self‐selection were the only ones to gain weight between sexual maturity and 28 weeks of age. 4. Nutrient intake patterns, related to each pullet's physiological age of sexual maturity, identified distinctive changes in protein intake and the selected protein: ME intake ratio of pullets fed by self‐selection. Pullets attempted to maintain a preferred protein:ME intake ratio, irrespective of the markedly different intakes of ME and protein at the two temperatures. 5. Pullets trained to self‐select nutrients from separate energy‐ and protein‐rich foods are better able to sustain egg output and body weight at sexual maturity when food intake is limited by high ambient temperatures.