Table 5.

Liver concentrations of Co, Cu, Mn, and Zn in beef cows that received diets containing supplemental INR (n = 95) or AAC (n = 95) during gestation^1,2

Item	INR	AAC	SEM	P-value
Co, mg/kg
Initial	0.165	0.155	0.009	0.44
Late gestation	0.586	0.678	0.024	0.01
Calving	0.584	0.550	0.114	0.83
Early lactation	0.140	0.154	0.009	0.31
Cu, mg/kg
Initial	74.0	66.9	11.0	0.65
Late gestation	125	81.9	12.9	0.02
Calving	118	42.9	9.9	<0.01
Early lactation	136	154	15	0.39
Mn, mg/kg
Initial	8.94	8.58	0.29	0.39
Late gestation	10.5	10.0	0.3	0.30
Calving	12.0	10.6	0.7	0.17
Early lactation	8.40	7.48	0.47	0.18
Zn, mg/kg
Initial	148	139	7	0.40
Late gestation	307	341	21	0.27
Calving	173	129	11	0.01
Early lactation	139	155	9	0.21

¹INR and AAC cows received the same amount of supplemental Co, Cu, Mn, and Zn from sulfate sources or Availa 4 (Zinpro Corporation, Eden Prairie, MN). Cows were assigned to the experiment at 117 ± 2 d of gestation (day 0).

²Liver samples were collected before the beginning of the experiment (day −30; initial), on day 97 (late gestation), upon calving when cows were 43 ± 0.5 d postpartum (early lactation), and at weaning (day 367) via needle biopsy (Arthington and Corah, 1995). Concentrations of Co, Cu, Mn, and Zn were determined by the Michigan State University Diagnostic Center for Population and Animal Health (East Lansing, MI; Braselton et al., 1997). Samples were collected from 30 cows of each treatment randomly selected on each sampling day.