Research at the Wageningen Institute of Animal Science in the Netherlands has found you can reduce hogs’ total urinary nitrogen excretion significantly by dropping the dietary crude protein without having to supplement with amino acids.

Researchers used dietary treatments for growing pigs of 16.5 percent, 14.5 percent and 12.5 percent crude protein. The level of crude protein did not influence the pigs’ feed intake or daily weight gain.

Nitrogen intake decreased when crude protein decreased. Results showed a 45 percent reduction in nitrogen excretion when moving from a 16.5 percent crude-protein diet to 12.5 percent crude protein, with the reduction coming almost entirely from urinary nitrogen. Slurry pH also dropped.

In another trial, mean ammonia emissions dropped 50 percent when dietary crude protein levels decreased from 16.5 percent to 12.5 percent.