The potential effect of age on proteins responsible for hepatic N metabolic capacity is poorly characterized. Two immunoblot studies were conducted to characterize the influence of age on the relative content of alanine transaminase (ALT), glutamine synthetase (GS), glutamate dehydrogenase (GDH), and aspartate transaminase (AST) in homogenates of liver biopsy samples obtained from mature young (Y; 3-4 yrs old, n = 12-13) versus old (O; 7–12 yrs old, n = 11–12) non-pregnant beef cows grazing the same mixed forage pasture for 20 d (Exp. 1) or fed enough of the same corn silage-based diet for 20 d to maintain body weight (Exp. 2). In Exp. 1, ALT and GS content were decreased 73 (P < 0.001) and 46% (P < 0.013) in O cows, respectively, whereas AST ( P < 0.645) and GDH (P < 0.195) did not differ. In terms of extracellular anionic amino acid transport capacity, the relative content of the system X AG− transporters GLT-1 (P < 0.135) and EAAC1 (P < 0.866) did not differ between O and Y cows. However, GTRAP3-18 content, a known inhibitor of EAAC1 activity, was increased (P < 0.001) 192% in O cows. Similarly, in Exp. 2, ALT and GS contents were decreased 61 (P < 0.009) and 71% (P < 0.001) in O cows, respectively, whereas GDH (P < 0.632), GLT-1 (P < 0.188) and EAAC1 (P < 0.169) were not altered but GTRAP3–18 content was increased (P < 0.049) 136%. These results indicate that the potential for hepatic production of alanine and glutamine is reduced in geriatric cattle, whereas urea synthesis is not. Source of funding: Univ. of Kentucky and Kentucky Agric. Exp. Stn.