| Abstrakt: |
The objective was to determine the influence of long-term supplementation (258 d) of a direct-fed microbial (DFM) and/or yeast cell wall (YCW) product on bacterial populations in beef steers. Single-sourced Charolais × Red Angus steers (n= 256; body weight = 246 ± 1.68 kg) were used in a randomized complete block design and blocked by location into one of four treatments: 1) fed no DFM and no YCW (Control); 2) fed only the DFM (DFM; Certillus CP B1801 Dry, 28 g/steer d−1); 3) fed only the YCW (YCW; Celmanax; 18 g/steer d−1); and 4) fed the DFM and the YCW (DFM+YCW). Steers were vaccinated for respiratory and clostridial diseases and treated for internal and external parasites at processing and individually weighed on days 1, 14, 42, 77, 105, 133, 161, 182, 230, and 258. To determine bacterial prevalence, fecal samples were collected on days 1, 14, 77, 133, 182, and 230 and environmental (pen area, feed, and water) samples were collected at the beginning of the week when cattle were weighed. No treatment × day interactions or treatment effects (P> 0.05) were observed between treatment groups at any sampling days for the bacterial populations. Samples on days 1, 133, and 182 had greater (P< 0.05) Clostridialevels compared to the other sampling points but were not different from each other. Clostridialevels were also greater (P< 0.05) on day 77 compared to days 14 and 230. Samples on days 77 and 230 had greater (P< 0.05) Clostridium perfringenslevels compared to the other sampling points but were not different (P> 0.05) from each other. Samples on days 1 and 14 had lower (P< 0.05) total Escherichia colilevels compared to the other sampling points but were not different (P> 0.05) from each other. Escherichia colilevels on day 77 were higher (P< 0.05) compared to days 133, 182, and 230. Little Salmonellaprevalence (1.5%) was observed throughout the study. This study had greater levels of Clostridiacompared to small and large commercial feedlots in the Church and Dwight research database, but C. perfringens, total and pathogenic E. coli, and Salmonellaprevalence were notably lower. Collectively, there were no appreciable treatment influences on bacterial populations. These data further indicate a low pathogenic bacterial challenge at the trial site, which could partially explain the lack of differences with DFM or YCW supplementation. The DFM and YCW used alone or in combination cannot be expected to show additional benefits when animals are relatively unstressed with a low pathogenic bacterial challenge.The DFM and YCW used alone or in combination in feedlot beef steers did not show productive benefits when animals were relatively unstressed with a low pathogenic bacterial challenge.The objective of this research was to determine the influence of long-term supplementation (258 d) of a direct-fed microbial (DFM) and/or yeast cell wall (YCW) product on bacterial populations in beef steers. Collectively, there were no appreciable treatment influences on bacterial populations. These data further indicate a low pathogenic bacterial challenge at the trial site, which could further explain the reasons for little differences. The DFM and YCW used alone or in combination cannot be expected to show productive benefits when animals are relatively unstressed with a low pathogenic bacterial challenge. |
