Effect of Copper Supplementation on Pre- and Postpartum Primiparous Beef Heifer and Progeny Hematological Parameters Fed Diets with or without Supplemental Sulfur

To assess the effects of Cu supplementation on pre- and postpartum primiparous beef heifer and progeny hematological parameters fed diets with or without supplemental S, 36 primiparous beef heifers (20 ± 0.5 mo of age; initial BW = 398 ± 24.9 kg) of predominantly Angus breeding were stratified by BW, BCS, and anticipated calving date and assigned to 12 pens (3 heifers/pen) for a 260 d study. Pens were assigned randomly to 1 of 4 treatments (2 × 2 factorial): 1) 0.15% S and 6 mg Cu/kg; 2) 0.15% S and 12 to 14 mg Cu/kg [6 to 8 mg from Cu₂(OH)₃Cl]; 3) 0.55% S (from Na₂SO₄) and 6 mg Cu/kg; or 4) 0.55% S (from Na₂SO₄) and 12 to 14 mg Cu/kg [6 to 8 mg from Cu₂(OH)₃Cl]. Diets were formulated to meet nutrient requirements during late gestation, with the exception of Cu and S. A cracked corn and soybean meal based supplement delivered each treatment starting at 170 ± 16 d of gestation through 150 ± 16 d in lactation. Heifers grazed mixed grass pasture and were provided predominantly fescue hay in quantities to ensure ad libitum access to forage. Heifer hematological parameters were assessed from blood samples collected d -113, -85, -57, -29, 0, 56, 85, 113, 142, and 150 ± 16 relative to parturition. Calf hematological parameters were assessed from blood samples collected 0, 31, 59, 86, 115, and 150 ± 6 d relative to birth. Orthogonal contrasts were used to determine the effects of Cu vs. S supplementation. Statistical significance was declared at P ≤ 0.10. No differences (P ≥ 0.58) were observed between treatments for heifer hemoglobin, hematocrit, white blood cell count, and red blood cell count. Supplementing heifers additional Cu decreased (P = 0.10; Cu main effect) the lymphocyte percentage and increased (P ≤ 0.10; Cu main effect) the neutrophil:lymphocyte ratio when compared to heifers not supplemented additional Cu. Supplementing heifers 0.55% S decreased (P ≤ 0.10; treatment × day) basophils at parturition when compared to heifers fed 0.15% S. Heifer pre- and postpartum Cu supplementation with or without supplemental S did not (P ≥ 0.31) influence progeny hematological parameters. These results suggest that the pre- and postpartum primiparous beef heifer immunity related blood profile (lymphocyte percentage) could be altered with a concomitant increase in inflammatory reaction (neutrophil:lymphocyte ratio) by Cu supplementation at 12 to 14 mg/kg of diet.