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

In Exp. 1, 240 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 0157: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 direct-fed microbial (DFM) treatments included: (1) control, lactose carrier only (Red); (2) 1x10^ 9 cfu of LA Strain NP51 plus 1 x 10^6 cfu of LA Strain NP45 plus 1 x 10^9 cfu of PF NP24 per animal daily (Green); (3) 1 x 10^9 cfu of LA Strain NP51 plus 1 x 10^9 cfu of PF NP24 per animal daily (Yellow); and (4) 1x10^6 cfu of LA Strain NP51 plus 1x10^6 cfu LA Strain 45 plus 1 x 10^9 cfu of PF NP24 per animal daily (Blue). 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, feed:gain (F:G), 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 difference {P = 0.08) among treatments was detected for ileal lamina propria (LP) thickness. The average LP thickness for Yellow and Green steers was less (P < 0.05) than the average for Red and Blue steers (0.38 vs. 0.45 mm). Moreover, Yellow and Green steers had a lower (P < 0.10) incidence of EC shedding than Red and Blue 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 decreased fecal EC shedding, which might be related to the results for ileal LP thickness. In Exp. 2, 660 steers were used to determine the effects of live cultures of LA and PF on performance, carcass, and intestinal characteristics of feedlot finishing steers. Cattle were fed a steam-flaked corn-based, 91% concentrate diet for an average of 118 d. Treatments included: (1) control, lactose carrier only (Red); (2) 5 x 10^6 cfu of LA Strain NP51 plus 5 X 10^6 cfu of LA Strain NP45 plus 1 x 10^9 cfu of PF NP24 per animal daily (Blue); and (3) 1 x 10^9 cfu of LA Strain NP51 plus 5 x 10^6 cfu LA Strain NP45 plus 1x10^9 cfu of PF NP24 per animal daily (Yellow). The steers used in this trial were from two distinct backgrounds. Background Group 1, classified as a short days on feed group (average BW at arrival = 352 kg), had grazed before arrival (BGl), and Background Group 2, classified as a long days on feed group (average BW at arrival = 314 kg), had been in a grower yard before arrival (BG2). As such, a split-plot design was used with background source as the whole-plot factor and DFM treatment as the split-unit factor. The overall F for background classification was significant (P <0.03) for both final BW and DMI; however, relative to DFM treatment no differences (P >0.67) were detected for DMI or BW data. The interaction for background classification and DFM treatment was significant (P <0.08) for both ADG and carcass-adjusted ADG. The simple effect ADG means and carcass-adjusted ADG means for all DFM treatments were different (P <0.01) between the two background classifications. In addition, within BGl DFM treatments were different (P = 0.09) for ADG; DFM treatments Red and Blue were not different (P = 0.70) from each other, but both were different (P <0.08) from Yellow.

Carcass-adjusted ADG was not different (P >0.23) for any DFM treatment within a background classification. As within ADG, the interaction of background classification and DFM treatment was significant (P <0.08) for both F:G and carcass-adjusted F:G. In contrast, the simple effect F:G means and carcass-adjusted F:G means for all DFM treatments were not different (P >0.12) across or within a background classification. Grade fat, taken at the 3/4 measure opposite the split lean surface between the 12th and 13th ribs was significantly different (P = 0.03) for DFM treatments. The interaction between background source and DFM treatment was significant (P <0.04) for both marbling score and the quality grade data. The simple effects for the Blue DFM treatment were different (P <0.01) across background source for both variables. The percentage of Choice vs. Select (42.51 vs. 57.49%, respectively) in BGl was reversed (64.20 vs. 35.80% respectively) in BG2. No other carcass characteristics relative to DFM treatment were different (P >0.24). The DFM treatments did not affect (P = 0.82) lamina propria thickness in cecal samples taken directly adjacent to the ileocecal junction. Overall, these data indicate that under the conditions of this study some of the live cultures of LA plus PF increased ADG in cattle that were classified as a short days on feed group. Furthermore, the DFM treatments used in this study did not alter LP thickness as in Exp. 1.