Table 3.

Carcass parameters of feedlot steers receiving diets containing (2 × 2 factorial arrangement): 1) monensin + tylosin (360 mg/steer daily from Rumensin 90 and 90 mg/steer daily from Tylan 40; Elanco Animal Health, Greenfield, IN) and 2) Y. schidigera extract (4 g/steer daily, as-fed basis; Micro-Aid Feed Grade Concentrate; DPI Global, Porterville, CA)¹

Item	Monensin + tylosin (A)			Y. schidigera extract (B)			P-values
	Yes	No	SEM	Yes	No	SEM	A	B	A × B
Dressing, %	62.9	62.6	0.2	62.7	62.9	0.2	0.25	0.44	0.23
Hot carcass weight, kg	386	385	3	384	388	3	0.88	0.30	0.32
Backfat, cm	1.23	1.19	0.04	1.20	1.22	0.04	0.48	0.80	0.46
Longissimus muscle area, cm2	95.7	96.8	1.2	95.9	96.6	1.2	0.51	0.67	0.72
Marbling	449	433	11	446	437	11	0.30	0.55	0.77
Yield grade	2.71	2.59	0.07	2.65	2.65	0.07	0.28	0.96	0.82
Carcasses choice or prime, %	66.7	61.7	6.2	61.7	66.7	6.2	0.57	0.57	0.57
Incidence of liver abscess,2 %	1.67	6.66	2.6	3.33	5.00	2.6	0.17	0.65	0.65

¹Steers were housed in four drylot pens equipped with electronic feed bunks (GrowSafe Systems Ltd, Airdrie, AB, Canada) that measured individual feed intake from day −14 to slaughter. Steers were slaughtered (STX Beef; Corpus Christi, TX) in three groups that contained an equivalent number of steers/treatment combination (36 steers on day 114, 36 steers on day 142, and 48 steers on day 170). Treatments were offered to cattle from day 0 to slaughter. Pens housed cattle from the same treatment combination, and cattle rotated across drylot pens every 14 d to account for any potential pen effect. Backfat thickness measured at the 12th rib; marbling score: 400 = Small⁰⁰, 500 = Modest⁰⁰; yield grade calculated as reported by Lawrence et al. (2010).

²Incidence of liver abscesses recorded as in Brown et al. (1975).