How Does Live Yeast Differ from Sodium Bicarbonate to Stabilize Ruminal pH in High-Yielding Dairy Cows?

Abstract

The objectives of this study were to evaluate the capacity of 2 dietary feed additives, sodium bicarbonate and live yeast Saccharomyces cerevisiae (strain Sc 47), in optimizing ruminal pH in dairy cows and to determine their modes of action. Three early lactating Holstein cows, fitted with ruminal cannulas, were allocated in a 3 x 3 Latin square design. They were given a total mixed ration as control diet (CD) at a daily feeding rate of 28.0 kg of dry matter (DM)/cow supplemented with 150 g/d of sodium bicarbonate (SBD) or 5 g/d of live yeast (YD) during a 21-d experimental period (14 d of diet adaptation, 4 consecutive days of measurement and sampling and 3 d of transition). The pH and redox potential (E(h)) were measured from 1 h before feeding to 8 h after feeding at 1-h intervals, and samples of ruminal fluid were taken at 0, 2, 4, 6, and 8 h after feeding for the determination of volatile fatty acids and lactate concentrations. Total tract apparent digestibility of the diet was also determined. Ruminal pH fluctuated between 6.53 at feeding and 5.57 at 5 h postfeeding. Mean pH was greater with SBD (6.21) and YD (6.14) compared with CD (5.94), showing that both additives had a pH stabilization effect. The E(h) varied from -88 mV at 1 h before feeding to -165 mV at 1 h after feeding. Mean E(h) and Clark's Exponent (rH) were lower with YD (-149 mV and 7.31, respectively) than with SBD (-137 mV and 7.85, respectively) and CD (-115 mV and 8.05, respectively), indicating that the yeast strengthened the reducing power of the milieu. Total volatile fatty acids were greater in SBD (95.3 mM) and YD (99.4 mM) compared with CD (85.3 mM). Acetate concentration was greater in SBD (60.8 mM) and YD (59.1 mM) compared with CD (53.2 mM). Propionate concentration was greater in YD (25.8 mM) than in SBD (20.0 mM) and CD (18.0 mM). Butyrate remained constant between diets. Mean total lactate concentrations were 16.5, 12.2, and 5.4 mM for CD, SBD, and YD, respectively, with a 67% decrease with YD. Total tract organic matter digestibility was greater for YD (66.6%) compared with SBD (61.7%) and CD (62.2%). The neutral detergent fiber digestibility was greater with YD (41.6%) compared with SBD (34.3%) and CD (29.6%), whereas acid detergent fiber digestibility was greatest in YD (32.3%), intermediate in SBD (24.4%), and lowest in CD (18.1%). By inducing a lower ruminal E(h) and rH, live yeast prevented accumulation of lactate and allowed better fiber digestion, whereas sodium bicarbonate seemed to act only as an exogenous buffer.

The effect of live yeast, <i>Saccharomyces cerevisiae</i>, and their metabolites on ciliate fauna, fibrolytic and amylolytic activity, carbohydrate digestion and fermentation in the rumen of goats

“…The increase in acetate concentration in the rumen of goats receiving a diet supplemented with live yeast might result from the increase in the number of cellulolytic bacteria, as the enhanced acetate level was associated with a higher activity of fibrolytic enzymes and with increased disappearance of NDF from hay incubated in sacco in the rumen. Our results are also in agreement with other studies focused on the effect of live yeast on the concentration of acetate in the rumen (Marden et al, 2008;Křížovă et al, 2011). In contrast, Brossard et al (2006) did not observe an increase in the ruminal acetate concentration in sheep.…”

“…The VFA concentration was significantly higher in goats fed the control diet or ration supplemented with live yeast than in animals receiving the ration enriched with yeast metabolites. Doležal et al (2005) and Marden et al (2008) reported that live Saccharomyces cerevisiae increased total VFA in the rumen of cows. In contrast to the cited authors, Brossard et al (2006) and Galip (2006) showed that live yeast cells did not modify total VFA, but according to Doreau and Jouany (1998), the effect of live yeast on total VFA in rumen of dairy cows was transient.…”

“…Conversely, MichaletDoreau et al (1997) observed a positive effect of live Saccharomyces cerevisiae cells on fibrolytic activity in the rumen. Similarly, the effect of live yeast cells on carbohydrate fermentation in the rumen is also inconsistent (Galip, 2006;Marden et al, 2008). In contrast to live cells, the role of yeast metabolites has been very rarely studied (Arakaki et al, 2000;Miller-Webster et al, 2002).…”

Microbial biodiversity of the liquid fraction of rumen content from lactating cows

“…Yeasts, in particular different strains or commercial products of Saccharomyces cerevisiae, have been tested on dairy cows with a number of positive effects such as increased dry matter intake (DMI) and milk production (Wohlt et al,1998;Dann et al, 2000); improved diet digestibility (Erasmus et al, 1992;Marden et al, 2008); stabilized rumen pH (Bach et al, 2007); and stimulated rumen bacteria growth (Newbold et al, 1995). However, there are also many studies with no or negative responses to yeast supplementation (Mwenya et al, 2005;Longuski et al, 2009;Chung et al, 2011), probably related to the strong influence of the basal diet, the variation in yeast strains and the different commercial formulations.…”

Effects of hydrolysed yeasts on ruminal fermentation in the rumen simulation technique (Rusitec)

“…Certain studies have indicated that supplementation of yeast to the diet may improve feed intake (Williams et al 1991), weight gain (Tripathi and Karim 2011), digestion (Jouany et al 1998), numbers of anaerobic and cellulolytic bacteria (Newbold et al 1995), ruminal pH value (Bach et al 2007) and alter the patterns of SCFA (Marden et al 2008). However, animal responses to yeast supplementation have not been consistent.…”