Abstract
The objective of this study was to evaluate the effects of Levucell SC (LY; Saccharomyces cerevisiae CNCM I-1077) supplementation on performance, feed efficiency, ruminal temperature, feeding behavior, and carcass quality traits in yearling steers. Forty-eight crossbred steers were randomly allocated into two treatments: (1) Control and (2) LY with two pen replicates per treatment (12 steers per pen). Steers were housed in pens equipped with GrowSafe and fitted with reticulo-rumen boluses. All steers were maintained on their respective dietary treatments until harvest to assess carcass traits. There were no differences amongst treatments in DMI, ADG, morbidity or mortality rates, ruminal temperature or F:G. Live-yeast supplemented steers had 17% greater (P = 0.05) backfat thickness than control steers, which resulted in a 13% increase in yield grade, with no differences in all other carcass traits. Live-yeast steers exhibited different feeding behavior patterns than control steers, such that LY steers approached the bunk 25 minutes earlier (P = 0.01) than control steers, had 22% greater (P < 0.05) bunk visit (BV) duration, 41% increased (P < 0.05) head down duration, 18% slower (P < 0.05) BV eating rates, and a tendency for 9% lower BV frequency. Meal criterion was 47% longer (P = 0.01) for LY steers resulting in a reduction (P = 0.07) in meal frequency. Additionally, LY steers consumed 27% longer meals (P < 0.05) that tended to be larger in size (P = 0.09). Although DMI was not different throughout the trial, LY displayed 10% decreased (P < 0.05) meal-eating rates due to longer meal lengths. Overall, LY steers approached the feed bunk sooner following feed delivery, ate fewer, but larger meals at a slower rate, and spent more time eating compared to control steers. Live-yeast supplementation clearly altered feeding behavior patterns, suggesting more favorable fermentation and the capability to mitigate metabolic stress in steers fed high-grain diets by altering meal patterns.