PSXI-8 Increasing dietary copper sulfate does not improve copper status of beef heifers consuming high-sulfate water.

Abstract Consuming high-sulfate water antagonizes Cu absorption in ruminants, but it is unclear whether greater Cu supplementation can supersede this antagonism. This study aimed to determine how increasing Cu-sulfate provision affects Cu status of heifers consuming high-sulfate water. Twenty Angus heifers (410±10.2 kg) were blocked by liver Cu concentration (495±23.7 mg Cu/kg dry matter (DM)), and randomly assigned to dietary treatments containing 17.4 (LCu, n=7), 26.1 (MCu, n=7), or 37.0 (HCu, n=6) mg Cu/kg of dietary DM. Diets consisted of 85% hay (8.7 mg Cu/kg DM) and 15% mineral pellet (DM basis). Dietary Cu was manipulated via Cu-sulfate inclusion in the pellet. Water contained 3,209±53.2 mg/L sulfate. Dry matter intake (DMI) and water intake were recorded weekly. Blood and liver biopsies were collected every 28 d over 12 weeks. Liver and plasma were analysed for Co, Cu, Fe, Mn, Mo, Se, and Zn. Plasma ceruloplasmin and serum albumin were also measured. Ruminal H2S gas concentration was measured pre-feeding (0730 h) and 3.5 hours post-feeding (1130 h) on d 40 and 80. Data were analyzed using GLIMMIX with fixed effect of block, treatment, day, and treatment×day interaction with day and time as repeated measures. Treatments did not affect (P≥0.10) DMI, water intake, or liver and plasma Cu. Ruminal H2S was increased post-feeding (P<0.01), which was likely associated with post-meal water consumption. Liver Cu declined by day, being greatest on d 0, intermediate on d 28, and least on d 56 and 84 (494.8, 429.3, 434.1, and 321.0 mg/kg DM, respectively; P<0.01). Plasma Cu was greater on d 0 and 84 (0.38 and 0.41 mg/L) than d 28 and 56 (0.30 and 0.35 mg/L; P<0.01). Liver Fe, Mn, Mo, and Zn and plasma Mn, Mo, Se, and Zn were affected by day (P≤0.01) but not treatment (P≥0.10). Liver and plasma Co were generally greater for LCu on day 28, 56, and 84 than for MCu and HCu (interaction, P<0.01). Within MCu, liver Se was greater on d 0 and lower on d 28 and 56, but not different from LCu and HCu (interaction, P<0.01). Plasma Fe was greater for LCu and MCu than HCu (P<0.01), and was least on d 0, intermediate on d 28 and 56, and greatest on d 84 (P<0.01). Treatment did not affect ceruloplasmin or albumin (P≥0.27), but ceruloplasmin was greatest on d 0 (27.1 mg/dL), intermediate on d 84 (10.5 mg/dL), and least on d 28 and 56 (8.1 and 9.4 mg/dL; P<0.01). Albumin was greater (P<0.01) on d 84 (4.17 g/dL) than d 0 and 56 (3.83 and 3.95 g/dL) but not different than on d 28 (4.04 g/dL). Increasing dietary Cu by increasing supplementation of Cu-sulfate did not improve Cu status of heifers consuming high-sulfate water.