Effects of Saccharomyces cerevisiae subspecies boulardii CNCM I-1079 on feed intake by healthy beef cattle treated with florfenicol and on health and performance of newly received beef heifers.

The effects of a live yeast supplement [Saccharomyces cerevisiae subspecies boulardii CNCM I-1079; ProTernative Stress Formula (PTSF) yeast, Ivy Natural Solutions, Overland Park, KS] on DMI, performance, and health of beef cattle were evaluated in 3 experiments. In Exp. 1, a pilot study was conducted with 10 healthy beef steers fed a 65% concentrate diet to evaluate the effects of florfenicol (s.c. in the neck vs. sterile water injection) on DMI. Steers injected with florfenicol had 15.6 (P = 0.092) and 22.2% (P = 0.015) decreases in DMI compared with controls on the day of and day after injection, respectively, with no differences for the remainder of the 7-d period. In the main study of Exp. 1, healthy beef steers (6 pens of 5 steers each/treatment) were fed the control or PTSF yeast diets (0.5 g of yeast x steer(-1) x d(-1)) for 5 d before being injected s.c. with florfenicol. Compared with the 5 d before injection, DMI decreased after injection, but it did not differ (P > 0.66) between treatments on the day of and day after injection. By the second day after injection, DMI tended (P = 0.107) to increase for steers fed PTSF yeast vs. control steers, with a trend for a similar pattern on the third day after injection (P = 0.197). No differences were noted between treatments for the remainder of the 7-d period or for the subsequent 2 wk. In Exp. 2, 3 loads of beef heifers (277 heifers; average initial BW = 230.3 kg) were shipped from auction barns and assigned randomly to 1 of 2 treatments (5 pens/treatment in each load) during 35-d receiving periods: 1) control = 65% concentrate receiving diet; or 2) PTSF yeast = 65% concentrate receiving diet with PTSF yeast added to supply 0.5 g of yeast x heifer(-1) x d(-1). All heifers were treated with florfenicol on arrival, and PTSF yeast heifers received approximately 1 g of yeast via an oral paste at the time of processing. Averaged over the 3 loads, treatments did not affect (P > or = 0.12) DMI, ADG, or G:F during the 35-d period, but the percentage of cattle treated once or more for bovine respiratory disease (BRD) was greater for control (P = 0.04) than for PTSF yeast heifers (24.0 vs. 13.78% respectively). In Exp. 3, 2 loads of beef heifers (180 heifers; average initial BW = 209.0 kg) that were not treated with antibiotic at the time of arrival processing were fed a 70% concentrate receiving diet and assigned the same 2 treatments as in Exp. 2. No differences (P > 0.72) were noted between treatments in ADG, DMI, and G:F for the 35-d receiving period, and BRD morbidity pooled across loads did not differ between treatments (40.2 vs. 33.1% for control vs. PTSF yeast). Providing PTSF yeast in an oral paste at the time of processing combined with the addition of 0.5 g of yeast x animal(-1) x d(-1) in the diet had little effect on receiving period performance; however, it decreased BRD morbidity in heifers given florfenicol on arrival but was without effect on BRD morbidity in heifers that did not receive a prophylactic antibiotic.