BICARBONATO DE SÓDIO E LEVEDURAS COMO ADITIVOS DE DIETAS PARA VACAS LEITEIRAS MESTIÇAS

Abstract

The objective in Experiment 1 was to evaluate the effect of the pH rise in sorghum silage through adding NaHCO3 on the milk yield and composition of crossbred primiparous cows (½ Holandesa ½ Jersey). The Experiment lasted 30 days divided in two periods of 15 days. The two treatments were sorghum silage plus 1.3% NaHCO3 (dry matter basis) and sorghum silage without additive. The experimental design was completely randomized in a single crossing-over scheme. Twelve lactating cows were assigned in two groups of six animals each, with average production of 15.7 liters/day ± 2.4 and 122 days ± 60 days in milking. The milk yield and composition were evaluated from the 13th to 15th days of each experimental period in four consecutive milkings. The objective in Experiment 2 was to study the addition of 2.2% NaHCO3 (dry matter basis), or yeast (20 g/cow/day or 0.2% dry matter basis) or the association of both in the same diet (sorghum silage + concentrates) offered to rumen cannulated dry cows. The following parameters were evaluated: dry matter intake, organic matter intake, NDF intake, dry matter in situ degradability, NDF in situ degradability (both at 30 hours), rumen pH, ruminal digesta dry matter, organic matter and NDF disappearance (Kd), ruminal digesta dry matter, organic matter and NDF turnover (Kt) and solid, liquid and total ruminal digesta. The Experiment lasted 56 days divided in four periods of 14 days. The treatments were the following: T1 = sorghum silage + concentrates; T2 = sorghum silage + concentrates + NaHCO3 (2.2% dry matter basis), T3 = sorghum silage + concentrates + yeast (20 g/cow/day or 0.2% dry matter basis) and T4 = sorghum silage + concentrates + NaHCO3 (2.2% dry matter basis) + yeast (20 g/cow/day or 0.2% dry matter basis). The experimental design was a 4x4 Latin Square and four crossbred rumen cannulated dry cows were utilized. In Experiment 1, there was no difference (P>0.05) on the milk yield, 3.5% fat corrected milk yield, milk fat content and production, protein content and production, lactose content and production and total solids content and production. It was concluded that the addition of 1.3% NaHCO3 (dry matter basis) in sorghum silage did not contribute to improve both milk production and composition of crossbred cows with average production of 15.7 liters/day ± 2.4 and 122 days ± 60 days in milking. In Experiment 2, there was no effect of the addition of NaHCO3 (2.2% dry matter basis) or yeast (20 g/cow/day or 0.2% dry matter basis) on the dry matter intake, organic matter intake, NDF intake, dry matter in situ degradability, NDF in situ degradability (both at 30 hours), ruminal digesta dry matter, organic matter and NDF disappearance rates (Kd), ruminal digesta dry matter, organic matter and NDF turnovers (Kt), rumen pH, and solid, liquid and total ruminal digesta fractions (P>0.05), compared to the control diet. Likewise, the association NaHCO3 (2.2% dry matter basis) + yeast (20 g/cow/day or 0.2% dry matter basis) did not have effect on the NDF intake, dry matter in situ degradability, NDF in situ degradability (both at 30 hours), ruminal digesta NDF Kd and Kt, rumen pH, and solid, liquid and total ruminal digesta fractions (P>0.05), compared to the diets with addition of NaHCO3 or yeast separately. On the other hand, there was difference of the association NaHCO3 + yeast on the dry matter intake, organic matter intake and ruminal digesta dry matter and organic matter Kd and Kt, compared to the diets with addition of NaHCO3 or yeast separately (P KEY WORDS: Digesta, disappearance, dry matter, fiber, intake, milk.