Effect of feeding das-59122-7 corn grain and non-transgenic corn grain to finishing feedlot steers

Article history: Received 27 October 2008 Received in revised form 8 February 2009 Accepted 9 February 2009 An experiment was conducted with eight ruminally-cannulated cows using a crossover design with2 periods to determine the effects of yeast supplementation on rumen fermentation. Holstein dairy cows in late lactationwere either supplementedwith0.5 g/hd/dof Saccharomyces cerevisiae, an active dry yeast (CNCM-1077, Levucell SC20 (r) SC, Lallemand Animal Nutrition) or not supplemented (control). A basal diet consistingof 60% forage and 40% concentrate (DMbasis)was fed once daily to both groups of cows throughout the entire experiment. Ruminal pH was measured continuouslyevery 22minusing a pHprobe thatwasplaced in theventral rumen sac for 6 consecutive days. Volatile fatty acid and ammoniaN concentrations in the rumenweremeasured on days 5 or 6 of the 12-d period for each cow and DM intake was monitored throughout the experiment. Datawere analyzedusing amixed-effectsmodelwith repeatedmeasures. Therewere no differences in dry matter intake between treatments. Mean ruminal pH was greater (Pb0.05) when yeast was supplemented (6.53±0.07) compared with the control (6.32±0.07). Average maximum and minimum ruminal pH were also greater (Pb0.05) when yeast was supplemented (7.01±0.09 and 5.97±0.08, respectively) compared with the control (6.80±0.09 and 5.69± 0.09, respectively). Time spent under the subacute acidosis threshold, pH less than 5.6, was lower (Pb0.05) with yeast supplementation compared with control cows. No difference was observed for ruminal ammoniaN concentrations (mean=14.0±1.2mg/dL)between treatments. Total VFA concentration (mM) in the rumen tended to be lower (P=0.10) in the yeast-supplemented cows (107.3±6.35) than in the control cows (122.4±6.35), which could be related to the greater pH observed with yeast supplementation. Supplementing dairy cows with active dry yeast in the current experiment increased the mean, minimum and maximum ruminal pH; decreased time spent in subacute rumen acidosis, and tended to decrease total VFA concentration in the rumen compared with control cows. Published by Elsevier B.V.