GROWTH-PERFORMANCE, APPETITE AND PLASMA AMMONIA CONCENTRATIONS IN HEIFERS FED INOCULATED LUCERNE PRIOR TO ENSILAGE, THEN SUPPLEMENTED WITH SODIUM-BICARBONATE

A study was conducted to explore the possibility of a synergistic effect of an inoculum of lactic acid bacteria and sodium bicarbonate in improving the nutritive value of lucerne silage. Twenty Holstein heifers (live weight 183 +/- 9.4 kg) were assigned to four dietary treatments consisting of: lucerne uninoculated or inoculated prior to ensilage and then either unsupplemented or supplemented with NaHCO3 (40 g kg-1 dry matter (DM)). The lucerne silage contained 320 g kg-1 DM and constituted 600 kg-1 diet DM. The animals were fed once daily for 90 d and samples of jugular blood were analysed for plasma ammonia and indices of blood acid-base status. Inoculation of lucerne reduced (P < 0.01) silage pH but had no other effect on silage composition. In the absence of NaHCO3, liveweight gain and organic matter intake were improved by inoculating lucerne prior to ensilage; however, in the presence of NaHCO3, inoculation reduced growth rate but had no major effect on intake. Dietary treatment did not (P > 0.05) affect the concentration of plasma ammonia or measures of blood acid-base status. The results suggest that NaHCO3 may have nullified any potential benefit of inoculating lucerne silage to improve its nutritive value for heifers.