Influence of dry matter and nitrogen intakes on fecal nitrogen losses in cattle

Dietary factors influencing loss of fecal nitrogen in Holstein steers have been examined in data on metabolism from forage diets. Two factors- total nitrogen and dry matter intake, accounted for a large part of the variation in fecal nitrogen. Nitrogen intak expressed as grams per kilogram dry matter intake more accurately accounted for variability in total fecal nitrogen than did nitrogen intake expressed as grams per animal per day. Data were from trials on 68 forages covering a range of nitrogen intakes and of nitrogen concentration in dry matter of forage. Correlations were .93 between total fecal nitrogen and dry matter intake, .90 between total fecal nitrogen and total nitrogen intake, and .95 between total fecal nitrogen and total fecal dry matter. However, at high and low nitrogen intake there was evidence of departure from a linear relationship. The relative usefulness of three regression analyses to estimate metabolic fecal nitrogen is discussed.