THE EFFECT OF CEMENT KILN DUST ON TISSUE ACCUMULATION OF TRACE MINERALS IN STEERS

Seven samples of cement kiln dust (CKD) were compared for particle size and rate of reactivity with dilute HCl. The majority of the CKDs had 80% of the particles less than 53 μm and had reaction rates (t50) of from 23 to 49 sec. A mash and a pelleted CKD diet were compared with a CKD-free control by feeding each diet to four Holstein steers for 336 days. The growth rate and feed consumption of the steers were not significantly different for any of the diets; however, the CKD pellet group grew faster with less daily dry matter intake so that the feed:gain ratio was less (P < 0.05) than for either of the other two groups. The lead content of tissues was elevated for steers fed both CKD diets; however, these differences were not significant. Zinc also appeared to be slightly elevated in liver, kidney and heart. The addition of CKD to diets modified the pH of gastrointestinal tract contents only in the colon. In all parts of the tract posterior to the omasum, the digesta from steers fed the CKD mash diet had lower soluble carbohydrate than digest from steers fed the control. The CKD pelleted diet produced the lowest soluble carbohydrate contents in digesta. Key words: Steer, cement kiln dust, lead, buffer, CKD