Any practice that can result in greater nitrogen efficiency of conversion into animal product either by reducing dietary protein or increasing animal productivity will ultimately reduce the amount of manure nitrogen available for volatilization. Most importantly, decreases in dietary protein will reduce manure nitrogen, especially from the urinary component. Urine nitrogen (mostly in the form of urea) can be quickly degraded to ammonia and lost by volatilization. In lactating dairy cows, first make sure that the diet supplies sufficient nutrients for the level of production (energy sources, protein, minerals, and vitamins). Fine-tuning rations by adjusting feeds (type and quantities) to accurately match the cow’s requirements of energy, protein degradability in the rumen, and by strategically using amino acid supplementation (usually Methionine) can lower nitrogen excretion in urine by as much as 20 to 30%, WHEN coupled with a reduction in dietary crude protein. Fact sheets describing aspects of nitrogen utilization by dairy cows can be found at National Feed Management for Livestock and Poultry.

Vinicius R. Moreira, LSU AgCenter Southeast Research Station