Table 4.

Main effects of MS and backgrounding estradiol benzoate and progesterone or estradiol benzoate and trenbolone acetate on cumulative and carcass adjusted performance in steer calves fed for 161 d in Exp. 1^a

	Mature sizeb			Implantc			Pooled
Item	SMS	LMS	P value	SS	CH	P value	SEM
n, steers	63	63	–	63	63	–	–
n, pens	8	8	–	8	8	–	–
Live weight basis
Initial body weight, kg	287	360	<0.01	324	323	0.83	1.0
Final body weight, kg	562	651	<0.01	608	606	0.65	3.7
Average daily gain, kg	1.71	1.81	0.02	1.77	1.75	0.71	0.024
Dry matter intake, kg	9.55	10.76	<0.01	10.23	10.07	0.34	0.111
Dry matter intake/MBSd, g/kg	102.0	100.9	0.34	102.1	100.8	0.26	0.81
Gain:feed	0.179	0.168	<0.01	0.173	0.174	0.51	0.0015
GEDe, Mcal/kg	4.61	4.87	<0.01	4.78	4.70	0.30	0.048
Carcass-adjusted basis
Final body weightf, kg	553	645	<0.01	603	595	0.12	3.2
Average daily gain, kg	1.65	1.77	0.01	1.74	1.69	0.21	0.024
Gain:feed	0.173	0.165	0.03	0.170	0.168	0.58	0.0023

^aShrink (3%) was applied to all body weights.

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

^cSS, 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.

^dMBS, metabolic body size, calculated as weight^3/4 (Kleiber, 1961).

^eGED, gain energy density, calculated as estimated retained energy divided by ADG.

^fCalculated as HCW divided by 0.625.