226 Evaluation of an active live yeast (Levucell SC, CNCM l-1077) on receiving and backgrounding phase growth performance in beef steers

Abstract

Abstract Low health risk, Continental × British steers (n = 199; off truck BW = 252 ± 32.1 kg) were received from two sources at the Ruminant Nutrition Center (RNC) in Brookings, SD in November 2019 and used in a 77 d feedlot receiving and backgrounding experiment. Steers were provided ad libitum access to long-stem hay and water at arrival. Steers were weighed, vaccinated for respiratory pathogens (source 2 only), clostridials, and administered moxidectin. Steers were allotted to pens (n = 20 pens; 10 pens/treatment; 8 to 9 steers/pen). Diets were based upon corn silage and dried distillers grains, treatments were 1) no direct fed microbial (DFM) fed (CON) and 2) DFM (Levucell SC, CNCM l-1077, at 10 g/hd/d providing 8 × 109 cfu, Lallemand Animal Nutrition, Milwaukee, WI; LC). Initial BW was the average of d -1 and d 1 BW (n = 176 steers; initial BW = 253 ± 27.6 kg). On d 21 steers received a 200 mg progesterone and 20 mg estradiol benzoate implant. Data were analyzed from d 1 to 47 (receiving period) and from d 1 to 77 (receiving and backgrounding period) as a RCBD; pen served as the experimental unit. On d 47 LC had greater BW (P = 0.01), ADG (P = 0.01) by 4.2%, and G:F tended (P = 0.10) to be 2.8% greater. Day 77 BW did not differ (P = 0.60), cumulative (d 1 to 77): ADG (P = 0.47), DMI (P = 0.66), and G:F (P = 0.56) were similar. In low–health-risk steers, LC improved performance during receiving; however, no influence to the addition of the DFM was detected from d 1 to 77. The confirmation of yeast counts showed the colonizing forming units to be above the expected level at start of trial but was found below expected level at end of trial. This may explain differences during the initial 47 d vs. 77 d results.