Table 1.

Distribution of isolates characterized in this study.

Treatmenta	Media used for selectionb	Sampling dayc					Total
		0	14	84	113	225
CON	BEA	24	20	25	25	23	119
	BEAE	6	8	17	16	9	58
	BEAT	9	9	19	22	19	79
T11	BEA	24	20	25	25	25	122
	BEAE	6	8	15	20	14	65
	BEAT	8	7	24	25	22	86
Total		77	72	125	133	112	519

^aSteers fed no antibiotics (control, CON) or tylosin phosphate (11 ppm; T11); administered continuously and withdrawn on day 197.

^bIsolates were streaked onto bile esculin azide agar (BEA) containing no antibiotics, or amended with erythromycin (8 μg/mL; BEA^E) or with tylosin (32 μg/mL; BEA^T).

^cSampling days began at day 0 (arrival at feedlot) prior to antibiotic administration and continued until the end of the feeding trial; sample day 0 and 14 were during the silage-based diet, day 84 during the transition diet and day 113 and 225 during the grain-based diet.