Energy intake regulation by layers according to diet, productivity and environment

Abstract

The voluntary nutrient intake and productivity of White Leghorn x Australorp crossbred layers given diets ranging in metabolizable energy (M.E.) from 11.30 to 13.81 MJ kg-1 were examined to determine their ability to adjust daily energy intake. Pullets housed on deep litter and in cages had a characteristic M.E. intake of 1.35 and 1.30 MJ per bird day respectively. Pullets in deep-litter pens regulated their energy intake until the M.E. content of the diet reached 12.97 MJ kg-1 but 'overconsumed' by 7.7 per cent when the dietary energy was raised to 13.81 MJ M.E. kg-1. Caged pullets were less able to regulate energy intake and 'overconsumed' by 8.0 and 14.8 per cent when the diet contained 12.97 and 13.81 MJ M.E. kg-1 respectively. During the period of production studied it would appear to be economic to use diets of up to 12.1 3 MJ M.E. kg-1 though the optimum may be less, depending on the production situation. Productivity was not significantly altered when the protein of the diets was either reduced according to predicted 'overconsumption', or lowered to as little as 14.2 per cent when the highest energy diet was given. Savings in the cost of high energy diets may, therefore, be achieved by adjusting the protein content for 'overconsumption'. Birds offered a diet containing 13.81 MJ M.E. kg-1 for five hours per day had a productivity and efficiency of energy utilization similar to that of birds on lower energy diets ad libitum. The greater cost per unit energy of such a diet, however, militates against restricted feeding of high energy diets under field conditions. An unexpected peak in egg production and efficiency of energy utilization was observed when access to the diet with an M.E. content of 13.81 MJ kg-1 was allowed between 11.00 a.m. and 4.00 p.m. each day. The possible significance of this observation is discussed.