Effects of chromium on performance and growth of feedlot steers

The effects of trace minerals from ruminant animal diets have been researched for nearly 100 years. During which time their effects on reproduction, immunity, growth, and proper development have been discovered. However, it has only been in the last 15 years that one of the more recently discovered essential trace minerals, chromium, has been extensively researched for use in beef cattle diets.; This dissertation is an in-depth study examining the effects of organic chromium on feedlot performance, carcass characteristics, and glucose clearance of ruminants. Steers receiving organic chromium at 200 ppb were not different from control steers for any performance parameters measured. However, feeding 400 ppb chromium reduced daily gain, dry matter intake, and feed conversion. Inclusion of organic chromium into steer diets increased longissimus muscle area over control steers. Additionally, chromium at 400 ppb also decreased final yield grade, reduced marbling score, and decreased carcass weight. Chromium did not affect serum cortisol levels or liver abscesses of feedlot steers. In addition, this dissertation utilized cell culture techniques to examine the effects of serum from steers fed organic chromium on muscle cell protein synthesis and glucose uptake. Cultured muscle cells treated with serum from chromium fed steers had higher levels of amino acid uptake an indicator of increased levels of protein synthesis. Glucose utilization was also increased by serum from organic chromium fed steers, over muscle cells treated with control serum. Glucose clearance, using sheep as a model, following a 21-day feeding period, was also improved by organic chromium. Sheep receiving organic chromium diets had lower glucose levels initially, and took less time to return to normal levels. This dissertation concludes that organic chromium affects carcass parameters of feedlot steers through changes in energy utilization (glucose uptake) and amino acid uptake (protein synthesis). These effects may be caused by alterations of endogenous hormone levels and other factors found in serum, due to increased cell sensitivity from glucose tolerance factor.