Nitrogen excretion is of concern because of its potential impact on the environment inside and outside the barn. Urinary nitrogen excretion can be reduced using dietary manipulations. Results indicate that a 2% reduction of dietary protein content throughout the grower phase reduced urinary nitrogen excretion by 22% without affecting performance. Phase feeding did not affect urinary nitrogen excretion or performance.

Lower total nitrogen excretion may reduce land base needed to apply manure in a sustainable manner. Lower urinary nitrogen excretion will reduce ammonia emission inside and outside the barn. The cost for implementing low protein diets will greatly depend on the fluctuating ingredient prices. For example at the present time for diets with an optimized digestible nutrient content, a 2% reduction in dietary crude protein increases the cost by $ 5 to 10 per tonne.