Effect of copper level and source (copper lysine vs copper sulfate) on copper status, performance, and immune response in growing steers fed diets with or without supplemental molybdenum and sulfur

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Abstract
One hundred twenty-six crossbred steers (218 kg initial BW) were used to determine the availability of Cu from copper lysine (CuLys) relative to CuSO4. Steers were assigned to pens (four replicates per treatment) based on BW and initial plasma Cu concentration and fed a corn silage-based diet supplemented with 0 or 5 ppm of Cu from either CuSO4 or CuLys. Half of the steers in each treatment were supplemented with 5 ppm of Mo and .2% S. Molybdenum and S supplementation increased (P < .10) growth rate during the first 21 d. Steers receiving CuSO4 gained more during the first 21 d than did control steers ( P < . 10) and steers receiving CuLys (P < .01). Growth, feed efficiency, and feed intake were not affected over the entire 98-d trial. Molybdenum and S supplementation decreased (P < .05) plasma Cu concentrations. Plasma Cu concentration was not affected by Cu source. Humoral immune response to ovalbumin was measured on d 7 and 77. Dietary treatment did not affect antibody production at either time. Cell-mediated immunity was measured in vivo on d 7 and 77 using phytohemagglutinin. In vivo cell reactivity was not affected by treatment on d 7 but was reduced (P < .10) by Mo and S supplementation on d 77. In vitro cell reactivity was measured on d 98 using a lymphocyte blastogenesis assay. Unstimulated lymphocytes from steers supplemented with Mo and S had lower (P < .10) uptakes of [3H]thymidine. There were no differences among treatments when lymphocytes were stimulated with pokeweed mitogen or phytohemagglutinin. (ABSTRACT TRUNCATED AT 250 WORDS)

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