Table 4.

Influence of dietary Zn and ractopamine inclusion on daily micro mineral intake, fecal and urine excretion, and mineral retention of steers during 5-d collection period

Dietary treatment	ZNTRT1			BA1
	CON2	SUPZN2	P value4	NON3	RAC3	P value4	SEM
Steers (n)	16	15		15	16
Mineral intake
Cu, mg/d	124	134	0.45	129	128	0.92	9.0
Fe, mg/d	1,617	1,678	0.71	1,656	1,640	0.92	111.4
Mn, mg/d	299	361	0.06	330	330	0.98	20.5
Zn, mg/d	322	1,534	<0.01	916	940	0.75	50.5
Fecal excretion
Cu, mg/d	94	103	0.24	97	100	0.72	4.7
Fe, mg/d	999	1,004	0.96	1,005	998	0.94	66.1
Mn, mg/d	229	247	0.34	236	239	0.87	12.8
Zn, mg/d	206	1,004	<0.01	578	632	0.38	41.1
Urinary excretion
Cu, mg/d	0.15	0.13	0.24	0.15	0.14	0.66	0.013
Fe, mg/d	1.92	1.98	0.77	2.00	1.90	0.65	0.160
Mn, mg/d	0.50	0.46	0.81	0.55	0.41	0.42	0.115
Zn, mg/d	1.09	1.99	<0.01	1.64	1.44	0.29	0.121
Mineral retention
Cu, mg/d	29	31	0.87	32	28	0.71	6.7
Fe, mg/d	616	673	0.49	649	640	0.91	56.2
Mn, mg/d	70	114	0.03	93	90	0.86	12.1
Zn, mg/d	114	529	<0.01	337	306	0.43	26.8

¹ZNTRT (mineral supplementation strategy); BA (β-adrenergic agonist supplementation strategy).

²CON (no supplemental Zn, analyzed 32 mg Zn/kg DM); SUPZN [CON + 60 ppm ZnSO₄ + 60 ppm zinc-amino acid complex (Availa-Zn; Zinpro, Eden Prairie, MN), analyzed 145 mg Zn/kg DM].

³NON (no supplemental ractopamine HCl); RAC (300 mg steer⁻¹ d⁻¹ ractopamine HCl; Actogain 45, Zoetis, Parsippany, NJ).

⁴ZNTRT × BA interaction was not significant (P ≥ 0.19).