Ruminants play a key role in society by converting fiber-rich plant resources into high-quality food that humans can eat. However, this conversion causes unavoidable losses of nitrogen in feces and urine that have the potential to become an environmental burden.
Three strategies have been suggested to reduce nitrogen emissions:
- improving the efficiency of animal use of feed protein
- reducing losses during manure storage and handling
- using crop rotations that better utilize manure nitrogen
Of these three options, improvement in animal feed use offers the quickest and easiest implementation.
Protein in, nitrogen out
There is no question that the most important factor determining total nitrogen excretion as manure (feces plus urine) in lactating dairy cows is total dietary nitrogen intake. Nitrogen intake is the principle driver of nitrogen excretion. Studies have shown that, by lowering dietary protein content, the excretion of this mineral can be significantly mitigated.
Diet also influences the relative proportion of nitrogen in urine compared to feces. In low protein diets, fecal nitrogen represents a larger proportion of total nitrogen intake, up to 50 percent, while urine nitrogen makes up as low as 25 percent. Upon the addition of extra dietary protein, the contribution of fecal nitrogen declines and urinary nitrogen loss rises to 60 percent of dietary intake.
Continue reading this article published in Hoard Dairyman.
