PS12-26. Effects of an Active Dry Yeast Saccharomyces Cerevisiae CNCM I-1077 on Beef Heifers’ Days on Feed and Growth Performance.

Abstract Effects of an active dry yeast (ADY) supplement on dry matter intake (DMI), growth performance, and feed efficiency of beef heifers consuming a high-fiber, barley-based finishing diet were evaluated. British crossbred heifers (n = 1,195; initial body weight = 393 ± 8.0 kg) were utilized in a commercial feedlot trial in Alberta, Canada. Upon arrival, heifers were randomly assigned to 12 pens, with approximately 100 heads per pen. Diets were based on dry-rolled barley and were formulated to progressively increase barley inclusion from 48 to 83% of dietary DM, while NDF decreased from 32 to 22% of diet DM (Table 1). Adaptation diets were fed for the initial 38d, followed by finishing diets until cattle reached market weight. Pens were allocated to one of two dietary treatments: 1) control (CON), consisting of the barley-based finishing diet containing monensin sodium at 22 mg/kg during the adaptation and 33 mg/kg during finishing phase; and 2) Saccharomyces cerevisiae CNCM I-1077 (SC-1077) at 8 × 10⁹ CFU/head/d, with the same basal diet, with monensin maintained at 22mg/kg DM diet DM (33% lower than CON). Tylosin phosphate was included in both treatment and control finishing diets at 11 mg/kg. Cattle were marketed as pen groups when deemed finished at approximately 580 kg BW. Dry matter intake was calculated from feed delivered to each pen, corrected for dietary dry matter content. Growth performance variables included average daily gain (ADG), gain-to-feed ratio (G:F), total gain, final BW, and days on feed (DOF). Data were analyzed using the mixed procedure of SAS with pen as the experimental unit and fixed effects of treatment. Treatment means were compared using Tukey–Kramer adjusted least squares means. During the first 38d, DMI did not differ (P = 0.47) between CON and SC-1077 cattle; similarly, DMI from d-39 to finish did not differ (P = 0.74) between control and SC-1077, and overall DMI was not different (P = 0.52) between treatments (Table 2). Final BW and total gain were similar (P = 0.31) between treatments (Table 2). Heifers receiving SC-1077 tended (P = 0.10) to have greater ADG, while G:F (P = 0.11) showed a numeric response compared with the control group (Table 2). Notably, SC-1077 heifers required 17 fewer DOF to reach market weight compared with controls (P = 0.03; Figure 1). In summary, SC-1077 supplementation in beef heifers fed a high-fiber, barley-based finishing diet had reduced DOF with a tendency for improved growth rate and feed efficiency without affecting DMI. These responses are consistent with previous research suggesting improved ruminal fiber digestion and nutrient availability. Overall, SC-1077 supported production efficiency in barley-based feedlot diets while enabling reduced ionophore inclusion, resulting in estimated savings of approximately $42.30 per head. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.