Table 6.

Effect of supplemental vitamin E (VE) on liver glutathione concentrations (µM/g of wet tissue) and superoxide dismutase activity (units/mg protein; 1 unit = the amount of enzyme required to dismutate 50% of the superoxide radical) of beef steers

	Supplemental VE treatment1					Contrast P-value
	CON	LOW	MED	HIGH	SEM2	Linear	Quadratic	Cubic
Glutathione
Day −33
Total	2.04	1.84	2.05	2.02	–	–	–	–
Oxidized	0.37	0.35	0.35	0.34	–	–	–	–
Reduced	1.68	1.49	1.70	1.68	–	–	–	–
Ratio4	0.232	0.251	0.223	0.215	–	–	–	–
Day 24
Total	2.24	2.11	1.84	1.77	0.126	0.01	0.25	0.85
Oxidized	0.40	0.37	0.34	0.32	0.021	<0.01	0.32	0.80
Reduced	1.83	1.74	1.50	1.46	0.116	0.02	0.28	0.79
Ratio4	0.223	0.217	0.234	0.214	0.0135	0.76	0.39	0.45
Superoxide dismutase
Day -33
Total	162	159	141	148	–	–	–	–
Mn	124	118	105	119	–	–	–	–
Cu/Zn	38.3	40.4	35.2	28.3	–	–	–	–
Ratio5	0.78	0.75	0.75	0.81	–	–	–	–
Day 24
Total	135.2	150.2	162.3	139.7	9.4	0.90	0.03	0.90
Mn	106.5	120.4	122.0	105.7	7.5	0.61	0.07	0.53
Cu/Zn	29.3	29.2	37.0	37.1	6.43	0.63	0.63	0.68
Ratio5	0.77	0.80	0.79	0.75	0.037	0.38	0.46	0.70

¹VE = vitamin E (ROVIMIX E-50 Adsorbate, DSM Nutritional Products, Heerlen, The Netherlands); CON = control (no supplemental VE); LOW = VE at 25 IU/kg DM; MED = VE at 500 IU per steer daily; HIGH = VE at 1,000 IU per steer daily.

²Highest SEM of any treatment reported.

³Values from day −3 (prior to treatment initiation) utilized as a covariate in analysis.

⁴Ratio = oxidized/reduced glutathione.

⁵Ratio = Mn-SOD/total-SOD.