Effects of live cultures of Lactobacillus acidophilus (strains NP45 and NP51) and Propionibacterium freudenreichii on performance, carcass and intestinal characteristics, and Escherichia coli 0157:H7 shedding of finishing beef steers

Direct-fed microbials are receiving attention from the feedlot industry. Thus, we conducted an experiment to test the effects of DFM on feedlot cattle performance. Two hundred forty beef steers (British and Continental; initial BW = 332.8 +/- 23.1 kg) were used to determine the effects of live cultures of Lactobacillus acidophilus (LA) and Propionibacterium freudenreichii (PF) on performance, carcass and intestinal characteristics, and prevalence of Escherichia coli O157:H7 (EC) shedding during the finishing phase. Cattle were fed a steam-flaked corn-based, 92% concentrate diet for an average of 170 d. The four treatments included: (1) control (CON) lactose carrier only; (2) 1 x 109 cfu of LA Strain 747 plus 1 x 106 cfu of LA Strain 45 plus 1 x 109 cfu of PF-24 per animal daily (G); (3) 1 x 10 9 cfu of LA Strain 747 plus 1 x 109 cfu of PF-24 per animal daily (Y); and (4) 1 x 106 cfu of LA Strain 747 plus 1 x 106 cfu LA Strain 45 plus 1 x 109 cfu of PF-24 per animal daily (B). A randomized complete block design was used with pen as the experimental unit (12 pens/treatment). No differences (P > 0.10) among treatments were detected for final BW, DMI, ADG, gain:feed, and hot carcass weight. In addition, dressing percent, longissimus muscle area, fat thickness at the 12th rib, percentage of internal fat, and yield grade did not differ (P > 0.10) among treatments. A trend (P = 0.08) was detected for treatment differences in ileal lamina propria (LP) thickness. The average LP thickness for Y and G steers was less (P < 0.05) than the average for CON and B steers (0.38 vs 0.45 mm). Moreover, Y and G steers had a lower (P < 0.10) incidence of EC shedding than CON and B steers. Overall, these data indicate that under the conditions of this study live cultures of LA plus PF did not greatly affect feedlot performance and carcass characteristics. Some of the cultures used in this study decreased fecal EC shedding, which might be related to the results for ileal LP thickness.