Metabolizable Energy in Feeding Systems for Pigs and Poultry

The major consideration in this paper is the suitability of a metabolizable energy system for pigs. For poultry there is no practical alternative since urine and faeces are voided conjointly. The correction to digestible energy of a feedstuff for energy in urine is usually small, but there are circumstances when this may be large. Furthermore there are insufficient data on metabolizable energy requirements for pigs, and on values for feedstuffs. It is concluded that even if a metabolizable energy system were adopted for ruminants and for poultry, introduction of such a system for pigs would be premature. It is suggested that a net energy system will eventually be introduced to describe the nutritional worth of livestock feedstuffs, but this is unlikely to appear in the immediate future, and probably in the first instance only for poultry.