Utilisation of dietary energy by poultry. II.—effects of indigestible organic matter and protein on the utilisation of metabolisable energy for growth

Rations compounded from individual cereals or from mixtures of cereals were fed to growing cockerels. When the levels of protein and metabolisable energy were closely controlled, the effect of indigestible material up to levels likely to be encountered in practice did not appear to have a consistent effect on the utilisation of metabolisable energy for gain in tissue energy, although a maize plus wheat diet which had the lowest content of indigestible material proved superior to other rations tested. A ration based on oats which contained the highest level of indigestible matter, gave poor growth, although utilisation of metabolisable energy for gain was normal. The poorer growth was attributed to reduced food intake owing to its relative unpalatability and bulk. When fed a diet containing a critical content of protein with an amino-acid imbalance, the birds tended to compensate by consuming more food and thus more energy than was normal for their weight and the excess energy was lost as heat.