Evaluation of the potential protein-sparing effects of sodium bicarbonate when added to grass silage for growing steers

Six Hereford-cross steers were used to determine whether or not the addition of sodium bicarbonate (NaHCO 3 ) to grass silage (GS) would reduce the need for supplemental protein from fish meal (FM). Grass silage (31% DM; pH 4.8) was either unsupplemented or supplemented with FM (10% of silage DM); NaHCO 3 was added at 0, 2, or 4% of silage DM. Supplementation with FM increased N retention (P   0.10) on feed intake or digestibility of organic matter (OM). Urinary N excretion decreased (P   0.10) of NaHCO 3 on N balance. Urinary excretion of bicarbonate (HCO 3 ) increased linearly (P   0.10) on urine pH or measures of blood acid-base status. Addition of NaHCO 3 increased silage pH to 6.5 but had no effect (P > 0.10) on voluntary feed intake, or digestibility of OM and ADF. The results indicate that the addition of NaHCO 3 to grass silage did not spare dietary protein but led to a shift in the partition of N between urine and feces. Key words: Steers, grass silage, sodium bicarbonate, nitrogen retention