THE SIGNIFICANCE OF PROTEIN SOLUBILITY IN BICARBONATE-INDUCED CHANGES IN NITROGEN UTILIZATION AND ACID-BASE BALANCE IN LAMBS

Abstract

Six crossbred wether lambs were fed six isonitrogenous (15% protein) diets according to a 6 × 4 incomplete latin square with four 24-d periods. The diets were arranged as a 2 × 3 factorial and contained high moisture ear corn (HMEC), supplemented with either brewer's dried grains (BDG) or linseed meal (LSM), containing 18% and 46% soluble protein, respectively. To each of these diets, sodium (Na) was either not added or added as NaHCO3 (4% of DM) or NaCl (2.8% of DM). Voluntary intake of organic matter (OM) was significantly (P < 0.05) increased with both NaHCO3 and NaCl supplementation but the response was greater with NaHCO3 than with NaCl. Nitrogen retention tended to be reduced with NaHCO3 supplementation; the reduction was greater with the BDG diet than with the LSM diet. Compared to NaHCO3, NaCl caused a smaller reduction in nitrogen (N) retention when added to the BDG supplemented diet but improved N retention when added to the LSM diet. Blood bicarbonate and base excess (BE) values increased (P < 0.01) with NaHCO3 addition, but the increment in blood bicarbonate and BE tended to be higher with the BDG than the LSM diet. It is concluded that NaHCO3 could impair nitrogen retention by elevating blood bicarbonate in ruminants not suffering acid stress. Key words: Bicarbonate, nitrogen balance, protein solubility, acid-base balance, lambs