This study characterized the effects of nutritionally induced metabolic acidosis with or without Gln infusion on acid-base balance, plasma AA, and plasma NEFA in sheep. In a randomized complete block design with a 2 x 2 factorial arrangement of treatments, 24 fully fleeced sheep (Rideau-Arcott, 63.6 +/- 5.9 kg of BW) were fed a control supplement (CS; 300 g/d of canola meal) or an acidosis supplement (AS; 300 g/d of NutriChlor; HCl-treated canola meal), offered twice daily at 0700 and 1100 h. Sheep were infused at 1400 h daily with 0.3 g of L-glutamine per kg of BW or saline via jugular vein catheters for 7 d. The sheep were individually housed and limit-fed a basal diet of dehydrated alfalfa pellets (1.75 kg/d; 90% DM, 22% CP, and 1.2 Mcal of NE(g)/kg on a DM basis) offered twice daily at 1000 and 1300 h. Blood and urine was sampled daily between 1100 and 1130 h, and blood samples were analyzed for hematocrit, plasma pH, gases, strong ions, AA, and NEFA, whereas urine was analyzed for pH. The AS reduced (P < 0.01) DMI, urine and plasma pH, blood urea, partial pressure of CO(2), strong ion difference, and plasma HCO(3)(-), and increased (P < 0.01) plasma K(+), Ca(2+), and Cl(-). The AS with saline infusion increased (P <or= 0.03) partial pressure of O(2) and plasma glucose, whereas AS with Gln infusion reduced (P < 0.01) partial pressure of O(2) and plasma glucose. The AS increased (P < 0.01) plasma lysine and reduced (P < 0.01) plasma taurine. Glutamine infusion increased (P = 0.04) plasma leucine with the CS treatment but had no effect (P = 0.89) with the AS treatment. Plasma 16:0, 18:2n-6, 18:3n-3, 20:4n-6, and total NEFA were increased and 18:0 was decreased (P < 0.001) in AS sheep compared with CS sheep. Infusion of Gln decreased (P < 0.05) 16:0, 18:2n-6, 18:3n-3, 20:4n-6, and total NEFA compared with saline infusion. Plasma cis-9, trans-11 CLA was elevated (P = 0.001) in AS sheep, whereas plasma cis-9, trans-11 CLA, regardless of the diets, was decreased (P < 0.02) with Gln infusion. These results show that despite some improvement in overall mobilization of NEFA, Gln infusion did not ameliorate the negative responses associated with metabolic acidosis.