Effects of copper oxide bolus administration on productivity and copper and zinc status in grazing beef calves supplemented with dried distillers grains

Abstract

<h2>ABSTRACT</h2> Corn by-product feed popularity, coupled with their relatively high S content, has prompted researchers to re-examine Cu oxide (CuO) bolus administration. A study was conducted to assess the effects of CuO bolus administration on productivity and Cu and Zn status in grazing beef calves supplemented with dried distillers grains. Calves (n = 74, yr 1; n=54, yr 2) were assigned randomly to 1 of 2 treatments: (1) a single intraruminal CuO (12.5 g) bolus or (2) nonbolus control for a growth trial (141 d, yr 1; 92 d, yr 2). Calves grazed predominantly bermudagrass [<i>Cynodon dactylon</i> (L.)] pastures. Dried distillers grains were offered at a rate of 0.75% of BW (as fed). Calves were weighed at 28-d intervals, and dried distillers grains were adjusted after each weigh day. Blood samples were collected for plasma Cu and Zn concentrations. There was no difference in final BW (<i>P</i> = 0.74, yr 1; <i>P</i> = 0.81, yr 2) or ADG (<i>P</i> = 0.77, yr 1; <i>P</i> = 0.75, yr 2) between bolused and nonbolused calves. Bolus administration did not influence plasma Cu (<i>P</i> = 0.65, yr 1; <i>P</i> = 0.26, yr 2) or Zn (<i>P</i> = 0.55, yr 1; <i>P</i> = 0.73, yr 2) concentrations compared with nonbolused calves. These results suggest that CuO bolus administration was ineffective at altering Cu and Zn status and overall performance in grazing beef calves supplemented dried distillers grains 0.75% (as fed) of BW. Dried distillers grains at 0.75% (as fed) of BW presumably did not create sufficient Cu antagonism.