Responses of sexually-maturing pullets to self-selection feeding under different temperature and lighting regimens

Challenges of Accurately Defining the Nutrient Requirements of Heat-Stressed Poultry

The number of factors that influence the nutrient requirements of heat-stressed poultry, through alterations in metabolism and biological responses, are much greater than those that influence the nutrient requirements of poultry at thermoneutral temperatures. Therefore, multiple dietary nutrient specifications adjusted for different intensities of heat stress experienced in different geographical locations, and for different management options used to combat such conditions, are likely to be required by poultry nutritionists. Financial constraints on the construction of suitable research facilities have limited the accumulation of knowledge concerning dietary nutrient specifications for heat-stressed poultry. Thus, input from commercial enterprises has contributed significantly to the accumulation of existing knowledge. Knowledge of the energy and amino acid requirements of birds during heat stress are best known, whereas vitamins and trace minerals remain among the least-researched groups of nutrients.

Influence of temperature, dietary energy, nutrient concentration and self-selection feeding on the retention of dietary energy, protein and calcium by sexually-maturing egg-laying pullets

1. On a daily temperature cycle of 25 to 35 degrees C and during the onset of lay, gross energy in droppings were increased significantly by 3 to 5%. There were no changes in energy metabolisability. Overall, less energy was excreted and energy metabolisability was improved on higher energy diets. 2. Crude protein and calcium losses decreased and their retention efficiencies increased with the onset of lay. Less protein and calcium were lost at the high temperature with corresponding increases in retention. Less protein and more calcium were lost on the higher energy diet. 3. Crude protein excretion was increased and calcium excretion reduced with self-selection feeding. Energy metabolisability and crude protein retention efficiency were reduced by this feeding practice.