Endogenous urinary metabolite excretion in the growing pig

Abstract

Endogenous urinary total nitrogen (N) and urea N excretions in the growing pig were measured using either the protein-free or regression method. Eighteen entire male pigs (28 kg liveweight) were randomly and equally allocated between six levels of feeding of a barley diet. Mean daily urinary total N and urea N excretions were determined. The regression of urinary metabolite output on dietary N intake extrapolated to zero N intake gave endogenous urinary total N and urea N excretions of 144.6 and 51.5 mg/kg0.75per day, respectively. Corresponding values for six of the pigs subsequently given a protein-free diet for 11 days, with endogenous excretions calculated over the final six days, were 163.3 and 62.2 mg/kg0.75per day. The urinary creatinine excretion of the barley-fed pigs was not related to dietary N intake. Mean daily urinary creatinine excretion was 53.1 ± 3.3 mg/kg0.75whereas that for pigs given the protein-free diet was 61.2 ± 2.0 mg/kg0.75. Although endogenous urinary metabolite losses tended to be higher for pigs on the protein-free feeding regime, endogenous urea N and creatinine N were close to 0.40 and 0.14 of endogenous total N respectively for pigs fed either the protein-free or barley diet. © 1987 Taylor & Francis Group, LLC.