1 23 Biological Trace Element Research ISSN 0163-4984 Volume 152 Number 3 Biol Trace Elem Res (2013) 152:333-342 DOI 10.1007/s12011-013-9636-5 Effect of Selenium and Vitamin C on Clinical Outcomes, Trace Element Status, and Antioxidant Enzyme Activity in Horses with Acute and Chronic Lower Airway Disease. A Randomized Clinical Trial Mohamed Ahmed Youssef, Sabry Ahmed El-khodery & Hussam Mohamed Mohamed Ibrahim