step three5 vs 6.3dos, n = 9cuatro, Nexp = 37, rsd = 0.05, P = 0.028, a = 6.4%). Where data were few, this impact was partly confirmed as a trend (n = 82 , P = 0.11) when the analysis was conducted within the experiment and with the volatile fatty acid (VFA) concentration used as a covariate. This trend suggested an eventual favorable effect of yeast on the pH of the medium. To go further in the analysis several sub-bases were built to respond to specific issues.
5 were considered (Jouany et al., 1998; Lynch and ), the influence of yeast supplementation was more marked (pH increase was 0.055 vs 0.024) but less significant (5.32 vs 5.26, n = 14, Nexp = 6, rsd = 0.05, P = 0.064, a = 7.1%). Pooling the data of Carro et al. (1992), Zelenak et al. (1994) and Lynch et al. (2002) allowed testing where there was any interaction between pH response and the level of cell wall (CW) in the diet or feed. The pH actually increased for feeds or diets having a higher level of CW, however there was no effect of yeast on pH and no interaction between CW and yeast.