EFFECT OF SODIUM BICARBONATE ON NITROGEN UTILIZATION AND FEED INTAKE BY LAMBS

Abstract

Eight wether lambs, four equipped with rumen cannulae and four intact, were assigned to four high-concentrate diets according to a 4 × 4 double latin square with 27-day periods. The basal diet consisted of barley and corn silage, the latter representing 30% of the dry matter (DM), and was either unsupplemented (9% dietary protein) or supplemented (15% protein) with brewers' dried grains. To each of the low protein (LP) and high protein (HP) diets, sodium bicarbonate (NaHCO3) was either not added or added at the level of 4% of the diet DM. There was a marked, though not statistically significant, improvement in nitrogen retention due to NaHCO3 inclusion, particularly when protein intake was low. Voluntary feed intake increased by 11% as a result of NaHCO3 addition but the effect was nonsignificant. Bicarbonate-induced changes in feed intake were unrelated to changes in rumen pH. A maximum ruminal osmolality of 303 mOsm/kg elicited by NaHCO3 addition did not appear to restrict feed intake. Rumen ammonia concentration tended to decrease as a result of NaHCO3 addition. Digestibility of organic matter and of DM was unaffected by the inclusion of NaHCO3 but digestibility of nitrogen tended to increase. It is suggested that NaHCO3 could have a protein-sparing effect when added to protein-deficient concentrate diets, and that bicarbonate-induced changes in feed intake may be related to its influence on protein status of ruminants. Key words: Bicarbonate, buffers, lambs, nitrogen utilization, feed intake