Table 5.

Main effects of MS and backgrounding estradiol benzoate and progesterone or estradiol benzoate and trenbolone acetate on carcass characteristics, EBF, and calculated frame score of steer calves fed for 161 d in Exp. 1

	Mature sizea			Implantb			Pooled
Item	SMS	LMS	P value	SS	CH	P value	SEM
n, steers	63	60	–	61	62	–	–
n, pens	8	8	–	8	8	–	–
HCW, kg	346	403	<0.01	377	372	0.12	2.0
Dressc, %	61.47	61.95	0.14	61.86	61.56	0.32	0.205
Back fat thickness, cm	1.20	1.31	0.10	1.27	1.24	0.67	0.041
LMA, cm2	79.84	85.64	0.01	83.33	82.16	0.48	1.129
LMA/HCW, 6.45 cm2/45.4 kg	1.63	1.50	<0.01	1.56	1.56	0.96	0.018
Calculated yield grade	3.05	3.32	0.02	3.18	3.19	0.96	0.067
Marbling scored	563	569	0.69	556	576	0.18	9.8
Kidney pelvic heart fat	2.14	2.01	0.18	2.03	2.11	0.41	0.064
Quality grade
Prime, %	0.00	0.00	–	0.00	0.00	–	–
High choice, %	1.68	3.17	0.59	0.00	4.87	0.08	1.990
Average choice, %	22.04	26.76	0.55	26.17	22.62	0.65	5.616
Low choice, %	65.17	51.42	0.13	55.40	61.18	0.52	6.384
Select, %	11.11	18.65	0.24	18.43	11.33	0.27	4.589
EBFe, %	29.34	30.61	0.01	29.97	29.98	0.98	0.259
AFBWe,f, kg	526	590	<0.01	562	554	0.19	3.6
EQSBWg, kg	270	301	<0.01	-	-	-	2.0
Calculated FSh	4.75	6.74	<0.01	5.87	5.62	0.18	0.117

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

^bSS, implanted with 20 mg estradiol benzoate and 200 mg progesterone on d 1 and with 24 mg estradiol and 120 mg trenbolone acetate on d 85; CH, implanted with 14 mg estradiol benzoate and 100 mg trenbolone acetate on d 1 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 (Tylutki et al., 1994).

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