Effects of live cultures of Lactobacillus acidophilus on performance and carcass characteristics of finishing beef steers

Selected strains of Lactobacillus acidophilus have been shown to decrease the presence of E. coli 0157 in the feces of finishing cattle. For this experiment, 300 beef steers (British and Continental breeding; initial BW = 272 ± 25.5 kg) were used to determine the effects of live cultures of Lactobacillus acidophilus strain 45 / and or strain 51 and Propionibacterium freudenreichii strain 24 on performance and carcass characteristics during the finishing phase. Steers were fed a steam-flaked corn-based, 92% concentrate diet for an average of 141 d. Five treatments were included in the experiment: (1) control, lactose carrier only (C); (2) 1 x 109 cfu of Propionibacterim freudenreichii (NP 24) plus 109 cfu Lactobacillus acidphilus (NP 51) per steer daily plus 106 cfu of Lactobacillus acidophilus (HV 45) per steer daily (H+); (3) 109 cfu Propionibacterium freudenreichii (NP 24) plus l07 cfu Lactobacillus acidophilus (NP 51) per steer daily (L); (4) 109 cfu Propionibacterium freudenreichii (NP 24) plus 108 cfu Lactobacillus acidophilus (NP 51) per steer daily (M); and (5) 109 cfu Propionibacterium freudenreichii (NP 21) plus 10^ Lactobacillus acidophilus (NP 51) per steer daily (H). Nutrition Physiology Corp., Indianapolis IN, supplied all prepackaged DFM treatments. A randomized complete block design was used with pen as the experimental unit (12 pens/treatment). Orthogonal contrasts (C vs. others; linear and quadratic effects of NP51 dose [L; M, and H]; and H vs. H+) were used to evaluate treatment means. No differences {P > 0.10) among treatments were detected for final BW, DMI, or hot carcass weight. A quadratic effect {P = 0.09) of NP51 level on F:G for d 0 to 56 was noted, and a linear effect of NP51 level for F:G (P = 0.09) was evident for d 0 to 84 of the feeding period. For ADG, a trend (P = 0.12) for a linear effect of NP51 dose level for d 0 to 28 was observed. The contrast of control vs. treated steers was significant (P = 0.01) for DP as well as for KPH and for yield grade (P = 0.04). Similarly, there was a tendency (P = 0.12) for greater longissimus muscle area (LMA) in control vs. treated steers. A trend (P = 0.15) for a quadratic effect of NP51 dose level also was evident for LMA, with lower values for the M vs. H and L treatments. The percentage of Choice carcasses responded quadratically (P > 0.04) to NP51 levels with the highest percentage of Choice carcasses in the M treatment group. Overall, these data indicated that the introduction of live cultures of LA plus PF had no ill effects on feedlot performance under the conditions of the trial. Moreover, the use of DFM to control the shedding of E. coli 0157 could be very beneficial for the food safety.