CASE STUDY: Multiple-Study Analysis of the Effect of Live Yeast on Milk Yield, Milk Component Content and Yield, and Feed Efficiency

A data set with dietary information and production responses was compiled from 14 research trials conducted internationally (160 observations representing 1,615 cows) that tested the effect of dietary inclusion of live yeast (Saccharomyces cerevisiae CNCM I-1077). Diet and feed analysis data for each study were entered into CPM (Cornell, Penn, Miner) Dairy 3.0.8 to estimate dietary nutrient parameters. Mean milk yield was 31.56 kg (SD = 6.45) with 3.75% milk fat (SD = 0.34) and 3.02% true protein (SD = 0.15). Mixed model analysis was conducted with CPM nutrients as main effects. Number of cows per treatment was included as a weighting factor, and experiment was included as a random effect. Live yeast significantly improved (P < 0.0001) 3.5% FCM yield (35.54 vs. 34.58 kg/d for live yeast and control) with the effect being greater for cows < 100 DIM (36.06 vs. 34.93 kg; P < 0.01) but still highly significant for cows > 100 DIM (33.81 vs. 32.83 kg; P < 0.005). Feed efficiency (kg 3.5% FCM/kg DMI) was improved (P < 0.001) with live yeast (1.75 vs. 1.70 for live yeast and control). There was no overall effect (P > 0.10) of live yeast on DMI. Although milk fat and protein content were slightly lower with the inclusion of live yeast, both milk fat yield (1.28 vs. 1.25 kg/d; P < 0.01) and milk true protein yield (1.02 vs. 1.00 kg/d; P < 0.0001) increased with live yeast.