Date of Award
Master of Science
Stephanie L. Hansen
Trace minerals (TM) serve functions in multiple enzymes and proteins that are essential to growth, development, and antioxidant status. As a result, TM are typically supplemented in ruminant diets to ensure animals maintain adequate status; however, a number of interactions can occur in the rumen that may inhibit the absorption of TM. Sulfur decreases the absorption of TM and can decrease cattle performance. The addition of dietary Mo to a diet containing high concentrations of S can also irreversibly inhibit the absorption of Cu. Hydroxy TM and injectable TM are novel supplements and little is known about the effectiveness of these sources with diets containing antagonists. Therefore, research was undertaken to 1) determine the effect of hydroxy (HYD) or inorganic (ING) TM supplementation on TM status and performance of beef steers fed high S diets, 2) evaluate the effect of TM repletion strategies in high S diets when sourced from an injectable TM or from increased concentrations of dietary TM, and 3) determine the impact of dietary S concentrations on the length of time an injectable TM would maintain improved TM status. In experiment 1, steers were supplemented with either HYD or ING TM within low S (0.27% S) or high S (0.54% S) diets. High S decreased Cu status and tended to decrease Zn status during the growing period, but did not affect Zn status in the finishing period. Additionally, there were interactions between S and TM source on liver Mn status; this, combined with the lack of effect on finishing period Zn status, suggest there may be an influence of diet on the S by TM interactions occurring in the rumen that alter the availability of TM. Interestingly, liver Cu concentrations were also greater for ING than HYD at the end of experiment 1, which is contrast to previous research stating HYD Cu and Mn were less ruminally soluble and more bioavailable than ING TM. Previous research has shown high S can decrease the absorption of Cu, Mn, and Zn. All animals had adequate status at the start of the trial and maintained this status throughout the study, suggesting the addition of national recommended concentrations may be sufficient to maintain TM status when dietary S is high (0.54%). There is an extensive amount of literature reviewing the effects of dietary organic TM in ruminants, however, less is known about how an injectable TM (Multimin90) may improve TM when dietary antagonists are present. A second trial was conducted to explore the effect of alternative TM supplementation strategies on TM status and performance steers when additional dietary antagonists were included. Steers were fed either a control (CON) diet containing supplemental TM at national recommended concentrations, or an antagonist (ANT) diet containing no supplemental Cu, Se, Mn, or Zn, and supplemental 0.3% S and 2 mg Mo/kg DM. At the end of the 90 d depletion period, ANT had a 90% decrease in liver Cu concentrations, and decreased liver Mn and Se status when compared to CON. The addition of Mo to the diet in the second experiment resulted in greater antagonism of TM absorption in comparison to the first experiment, however both trials recorded the high antagonist diet to decrease Cu and Mn, and some markers of Zn status. After the depletion period, three supplementation strategies were utilized. Steers received either a trace mineral injection and supplemental dietary TM at national recommended concentrations (ITM), increased concentrations of dietary TM at 150% of national recommended concentrations from a blend of 25% organic and 75% inorganic TM (BLEND), and increased concentrations of dietary TM at 150% of recommended national concentrations from only inorganic TM (ING; NASEM, 2016).Even in the face of dietary antagonists, all TM supplementation strategies improved the TM status of steers, such that Cu and Se status was increased in ITM on d 14, BLEND was improved on d 28, and ING reached similar concentrations as ITM and BLEND on d 42. Liver Mn status was affected by repletion strategy and there were no effects of depletion diet or TM supplementation on liver Zn concentrations. The lack of a reliable biomarker for Mn and Zn status may be the reason for the lack of differences in status. To the author’s knowledge, this is the first time a study has reported the effect of injectable TM Multimin90 on TM status of cattle fed high antagonist diets. Additionally, there were no effects of repletion strategy within depletion diet, suggesting all three supplementation strategies can improve TM status even in the presence of a high antagonist diet. Previous research has shown injectable TM to improve TM status for at least 30 d, and the present study shows the effect may extended to at least 42 d. There were few recorded effects of treatment on the performance of beef steers in the two trials, and neither experiment reported change in final BW or ADG. In the trial that utilized a diet high in S and Mo, dietary antagonisms decreased DMI and increased G:F during the TM repletion period. The improved G:F could be due to the increase TM in the repletion period, which may have indirectly caused some compensatory gain. Overall, this research supports that of others indicating diets containing high S and high antagonists decrease the TM status of feedlot cattle. The effects of hydroxy TM supplementation in diets containing high S were inconsistent, especially within Mn status, however these differences may be attributed to the interactions of S and TM within diet type. Regardless of if steers were fed a control or antagonist diet during the depletion period of the second trial, all TM supplementation strategies improved TM status of Cu and Se by 42 d. These results suggest injectable TM and high concentrations of dietary TM may be able to overcome TM deficiencies in feedlot cattle and improve status. Further research is warranted to solidify the implications of how hydroxy TM may improve TM status in a high S diet, and additional research should be done to determine reliable and repeatable biomarkers for Mn and Zn status in cattle.
Sarah Jeanette Hartman
Hartman, Sarah Jeanette, "Implications of trace mineral supplementation strategies to overcome the effects of high antagonist diets in feedlot cattle" (2017). Graduate Theses and Dissertations. 15316.