THE EFFECT OF SODIUM BICARBONATE, SODIUM BICARBONATE PLUS MAGNESIUM OXIDE OR BENTONITE ON THE INTAKE OF CORN SILAGE BY LACTATING COWS

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Abstract
Four trials, each employing 10 cows were designed as 2 × 2 latin squares, with each experimental period consisting of a 1-wk preliminary period and a 4-wk period for data collection. The objective of the experiments was to determine the effectiveness of either sodium bicarbonate (NaHCO3), NaHCO3 plus magnesium oxide (MgO) or bentonite as buffers when they were mixed with corn silage just prior to feeding. The treatments compared were: Trial I, control vs. NaHCO3 (180 g·cow−1·day−1); Trial II, control vs. bentonite (300 g·cow−1·day−1); Trial III, control vs. NaHCO3 (180 g·cow−1·day−1) plus magnesium oxide (MgO, 60 g·cow−1·day−1) and Trial IV, NaHCO3 (180 g·cow−1·day−1) vs. bentonite (300 g·cow−1·day−1). Silage dry matter intakes (SDMI) were 10.61 vs. 10.93 and milk yields were 26.6 vs. 29.3 kg/day for control vs. NaHCO3 in Trial I; 10.03 vs. 10.39, and 29.5 vs. 30.1 for control vs. bentonite in trial II; 10.62 vs. 10.69, and 23.6 vs. 24.7 for control vs. NaHCO3 + MgO in Trial III and 11.49 vs. 10.79, and 29.4 vs. 29.5 for NaHCO3 vs. bentonite in Trial IV. In the latter trial cows fed silage supplemented with bentonite had significantly lower milk fat and protein percentages and rumen pH compared to those supplemented with NaHCO3. Similarly in Trial II cows fed bentonite had lower rumen pH and milk protein percentage than the control cows. It was concluded the bentonite did not act as a buffer and was not beneficial when added to corn silage just prior to feeding. NaHCO3 improved milk yield in one trial and milk fat percentage but the degree of response did not warrant its routine use as a supplement to corn silage. Key words: NaHCO3, MgO, bentonite, corn silage, lactating cows, buffers