Table 8.

Main effects of MS and backgrounding estradiol benzoate and progesterone on carcass characteristics, estimated EBF, and calculated frame score of steer calves fed for 168 d in Exp. 2

	Mature sizea			Implantb			Pooled
Item	SMS	LMS	P value	NI	SS	P value	SEM
n, steers	77	75	–	76	76	–	–
n, pens	10	10	–	10	10	–	–
HCW, kg	363	414	<0.01	385	392	<0.01	1.0
Dressc, %	61.92	62.75	<0.01	62.20	62.47	0.23	0.151
Back fat thickness, cm	1.39	1.58	<0.01	1.48	1.50	0.71	0.033
LMA, cm2	83.76	89.31	<0.01	86.18	86.88	0.34	0.495
LMA/HCW, 6.45 cm2/45.4 kg	1.62	1.53	<0.01	1.59	1.56	0.07	0.008
Calculated yield grade	3.15	3.45	<0.01	3.29	3.31	0.73	0.050
Marbling scored	618	621	0.77	623	616	0.54	7.6
Kidney pelvic heart fat	1.95	1.87	<0.01	1.92	1.90	0.22	0.013
Quality grade
Prime, %	3.88	5.22	0.69	5.21	3.89	0.70	2.438
High Choice, %	13.00	12.01	0.86	10.56	14.45	0.48	3.892
Average Choice, %	40.07	36.15	0.62	41.93	34.29	0.33	5.601
Low Choice, %	39.19	38.52	0.93	34.33	43.38	0.26	5.696
Select, %	3.86	8.10	0.27	7.97	3.99	0.30	2.732
EBFe, %	30.72	32.23	<0.01	31.42	31.53	0.69	0.202
AFBWe,f, kg	529	581	<0.01	550	560	0.07	3.4
EQSBWg, kg	288	316	<0.01	–	–	–	1.7
Calculated FSh	4.82	6.48	<0.01	5.52	5.78	0.05	0.085

^aSMS, smaller mature size; LMS, larger mature size.

^bNI, nonimplanted during backgrounding-phase, implanted with 24 mg estradiol and 120 mg trenbolone acetate on d 85; SS, implanted with 20 mg estradiol benzoate and 200 mg progesterone on d 2 and with 24 mg estradiol and 120 mg trenbolone acetate on d 85.

^cCalculated as HCW divided by final body weight.

^dSmall⁰, 500, Modest⁰, 600.

^eEstimated using equations of Guiroy et al. (2001).

^fAFBW, final shrunk weight at 28% empty body fat.

^gEQSBW, equivalent shrunk body weight (Tyultki et al., 1994).

^hEstimated using final shrunk weight at 28% EBF and data from Fox et al. (1992).