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

Abstract

Six Hereford-cross steers were used to determine whether or not the addition of sodium bicarbonate (NaHCO3) 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); NaHCO3 was added at 0, 2, or 4% of silage DM. Supplementation with FM increased N retention (P < 0.01) but had no effects (P > 0.10) on feed intake or digestibility of organic matter (OM). Urinary N excretion decreased (P < 0.05) linearly with the addition of NaHCO3 but due to an increase in fecal N there was no significant effect (P > 0.10) of NaHCO3 on N balance. Urinary excretion of bicarbonate (HCO3) increased linearly (P < 0.01) with NaHCO3 addition, but there was no effect (P > 0.10) on urine pH or measures of blood acid-base status. Addition of NaHCO3 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 NaHCO3 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