Effect of sodium bicarbonate and magnesium oxide in an alfalfa-based total mixed ration fed to early lactating dairy cattle.

Forty-eight lactating Holstein cows were fed a total mixed ration of 57% concentrate and 43% forage (dry basis) for 12 wk postpartum. Treatments consisted of 1) no added buffers, 2) .4% MgO, 3) .8% NaHCO3, and 4) .8% NaHCO3 plus .4% MgO of the total ration DM. Body weight, DM intake, and milk yield and composition were unaffected by treatment. Gross efficiency of milk production was decreased by the addition of NaHCO3 or MgO. Buffer supplementation had no effect on ruminal volatile fatty acid concentration or blood chemistries.