Plasma levels of arginine, ornithine, and urea and growth performance of broilers fed supplemental L-arginine during cool temperature exposure

Two experiments (Experiment 1 and 2) were conducted to evaluate growth perf ormance, ascites mortality, and concentrations of plasma Arg, urea, and orn ithine in male broilers raised in floor pens (2 x 4 factorial experiment, s ix pens for treatment) and exposed to tool temperatures averaging 16 C afte r 21 d of age. Broilers were fed low- or high-CP diets in both Experiments. In Experiment 1, Arg treatments consisted of control (no supplemental Arg) ; 0.15 or 0.3% supplemental Arg in the diet (low- and medium-Arg feed, resp ectively); and 0.3% supplemental Arg in the drinking water (Arg-water). Arg inine levels were increased in Experiment 2 and consisted of the following: control (no supplemental Arg); 0.3 or 0.85% supplemental Arg in the diet ( medium- and high-Arg feed, respectively); and 0.6% supplemental Arg in the drinking water (Arg-water). The water treatment followed a 3-d cyclic regim en, with supplemental Arg being provided for 24 h, followed by tap water fo r 48 h. When the broilers reached 37 d of age and all groups had consumed t ap water for the previous 48 h, blood samples were collected from one bird per pen (Time 0, 0700 h); then supplemental Arg was provided in the Arg-wat er group, and additional blood samples were collected from the control and Arg-water groups at 3, 6, 12, and 36 h after Time 0. Plasma amino acids wer e analyzed using HPLC. Birds fed the high-CP diet were heavier at 49 d than birds fed the low-CP diet in Experiment 1, but not in Experiment 2. No dif ferences were found in feed conversion or ascites mortality due to CP or Ar g treatments in either experiment. In both experiments, plasma Arg was simi lar for all groups at Time 0, but increased in the Arg-water group at 3, 6, and 12 h after Arg was provided in the water. Within 12 h after returning to tap water, plasma Arg levels of the Arg-water group did not differ from the control group. Plasma urea and ornithine were parallel to plasma Arg co ncentrations, and the high-CP diets resulted in higher plasma levels of ure a and ornithine compared with low-CP diets. These results indicate that kid ney arginase was readily activated by Arg provided in the water, resulting in an immediate increase in plasma urea and ornithine. Plasma Arg was incre ased significantly, but no effects were observed in ascites mortality.