Table 7.

Hot carcass weight and carcass characteristics of beef steers fed to 0, 28, or 56 d on feed and given maintenance or ad libitum intake and control or zilpaterol hydrochloride treatment

Item	0	28 A	28 M	56 AZ	56 AC	56 MZ	56 MC	SEM	P-value	0 vs. 28	0 vs. 56	28 vs. 56	M vs. A	C vs. Z
Hot carcass weight, kga	361c	383bc	353c	420a	404ab	380bc	364c	11.4	<0.01	0.67	0.03	0.03	<0.01	0.10
Dressed carcass yieldb, %	61.7c	62.4bc	62.0bc	63.2ab	61.4c	64.1a	61.7c	0.52	<0.01	0.41	0.08	0.27	0.47	<0.01
Adj. 12th rib fab thickness, cm	1.63cd	2.15bc	1.68cd	2.52ab	2.72a	1.92cd	1.52d	0.19	<0.01	0.22	0.01	0.12	<0.01	0.61
LM area, cm2	85.81	89.03	85.97	93.55	89.11	87.82	88.39	0.45	0.53
KPH, %	2.16	2.06	1.96	1.98	2.53	1.87	2.00	0.21	0.09	0.45	0.73	0.52	0.05	0.02
USDA calculated yield gradec	3.3cd	3.8bc	3.3cd	4.3ab	4.7a	3.6bcd	3.1d	0.27	<0.01	0.46	0.05	0.12	<0.01	0.81
Marbling scored	420	441	419	453	446	445	398	49.6	0.38
Skeletal maturitye	138	145	140	145	146	145	160	10.4	0.79
Color scoref	5	5.4	5.1	5.0	4.9	5.1	5.4	0.5	0.90
Canadian ribeye lengthg	1.38	1.75	2.00	2.13	1.88	1.75	1.75	0.25	0.49
Canadian ribeye widthg	2.13	2.25	2.00	1.88	2.00	1.50	1.75	0.24	0.43
Canadian muscle scoreg	1.50	2.00	2.00	2.13	1.88	1.38	1.75	0.30	0.53
Canadian fat classg	5.88cd	8.13abc	6.76cd	8.63ab	9.13a	7.63bcd	6.63d	0.58	<0.01	0.36	0.05	0.20	<0.01	0.62
Canadian calculated lean yieldh	53.9ab	52.6abc	54.6a	51.9bc	51.1c	52.6abc	54.6a	0.92	0.03	0.81	0.17	0.16	<0.01	0.47

^aHot carcass weight includes kidney-pelvic-heart fat.

^bBW used was unshrunk because steers were not allowed feed and water for 9 h.

^cUSDA calculated yield grade = 2.5 + (2.5 × FT) + (0.2 × KPH) + (0.0038 × HCW) − (0.32 × REA), where FT = adjusted 12th rib fat depth in cm, KPH = percentage of kidney-pelvic-heart fat, HCW = hot carcass weight in kg, and REA = longissimus muscle area in cm².

^d100 = practically devoid⁰⁰, 300 = slight⁰⁰, 500 = modest⁰⁰, 700 = slightly abundant⁰⁰, and 900 = abundant⁰⁰.

^e100 = A⁰⁰ and 500 = E¹⁰⁰.

^f1 = light pink, 2 = pink, 3 = dark pink, 4 = light cherry red, 5 = cherry red, 6 = dark red, 7 = very dark red (1/3 dark cutter), 8 = maroon (2/3 dark cutter), and 9 = dark maroon (full dark cutter).

^gCanadian ribeye length and width, muscle score, and fat class calculated using Yield Ruler developed by Lacombe Research Station (CBGA, 2001).

^hCanadian calculated yield grade calculated as estimated lean % = 63.65 + (1.05 × muscle score) − (0.76 × fat class) where estimated lean yield of 59% or ≥ YG1, 54–58% = YG2, and 53% or ≤ YG3.