Evaluation of nitrogen and organic matter balance in the feedlot as affected by level and source of dietary fiber.

A trial was conducted to determine the effect of level and source of dietary fiber on N and OM excretion by cattle on finishing diets. One hundred twenty steers were stratified by weight and allotted to one of the following treatments: 7.5% roughage (7.5% R), wet corn gluten feed (WCGF; 41.5% of dietary DM), and all-concentrate (All Con) diet. Cattle were fed for 87 d during the summer with 23.7 m2 of pen area per animal. Steers fed the WCGF diet had heavier final weights, greater DMI, and higher ADG (P < .01) than the 7.5% R and All Con treatments. Steers fed All Con had lower (P < .01) DMI than the other two treatments. Nitrogen and OM mass balances in the feedlot were quantified. Main components were nutrient input, retention, and excretion. Nitrogen and OM intake of steers fed WCGF were greater (P < .05) than those of steers fed the other treatments. The WCGF treatment had a greater percentage of fecal N output (P < .05). The All Con treatment had a greater (P < .01) percentage of urinary N than WCGF and 7.5% R diets. Steers fed the WCGF treatment excreted more (P < .01) OM compared with the other treatments, which led to more N and OM being removed in manure at cleaning. The All Con treatment had more (P < .01) N and OM in runoff than the other treatments. Nutrition can change site of fermentation, which affects the composition of excreted material; however, total amount of N excreted may be more important than route of excretion in decreasing N losses to the environment and maximizing recovery in manure.