Diet formulation has a direct impact on the efficiency of use of nutrient and energy by pigs and poultry and, consequently, it affects nutrient and waste flow at farm level. All the compounds found in the manure, or emitted into the air, originate from the fraction of the diet which is not retained by the animals. The improvement of efficiency of nutrient retention by pigs and poultry is an efficient way to reduce excretion and emission from the animals. Changing the composition of the feed is efficient to modify the chemical properties of excreta in order to reduce the gaseous emissions and the production of odours. Changing the composition if the feed may allow to better adapt the composition of excreta to their future use for biogas production or as fertilisers. Innovations in the development of enzymes and amino acid production have been and are still important levers for the development of low environmental impact feeding strategies for pigs and poultry. The development of feeding strategies for reducing N and P excretion by pigs and poultry requires a good knowledge of nutrient bioavailability in feed ingredients and a precise evaluation of requirements. Phase feeding is required for practical application of improved feeding strategies. It is facilitated by the use of computerised feeding systems with the perspective of precision feeding.