TABLE 1.
Numbers of E. coli isolates from pens housing steers fed silage- or grain-based diets containing antimicrobial agents
| Parameter | Antimicrobial agent(s) administereda
|
SE | Pb | |||||
|---|---|---|---|---|---|---|---|---|
| Control | TET-SUL | TET | VIR | MON | TYL | |||
| No. of E. coli (log CFU swab−1): | ||||||||
| Silage-based dietc | 5.32 a | 5.00 b | 5.00 b | 5.18 a | 5.16 a | 5.13 a | 0.07 | 0.0494 |
| Grain-based diet | 5.32 | 5.36 | 5.24 | 5.49 | 5.30 | 5.37 | 0.02 | 0.1755 |
| Overall | 5.32 | 5.13 | 5.09 | 5.29 | 5.21 | 5.22 | ||
| SE | 0.02 | 0.067 | 0.05 | 0.05 | 0.066 | 0.03 | ||
| Silage vs graind | 0.80 | 0.02 | 0.038 | 0.01 | 0.212 | 0.01 | ||
a
Control, no antimicrobial agents added to the diet. The TET-SUL, TET, VIR, and TYL treatments are described in detail in Materials and Methods.
b
Effect of administration of antimicrobial agents.
c
Within a row, values followed by different letters differ.
d
That is, the effect (P value) of the diet formulation within an antimicrobial feeding group.