An insurance company did not violate its duties to a policyholder by refusing to authorize the humane destruction of her champion show horse, a federal appeals court held.The 7th U.S. Circuit Court of Appeals upheld a trial judge’s decision to grant summary judgment in favor of the Great American Assurance Co. in a lawsuit filed by Julie Greenbank.Greenbank maintains Great American breached a $500,000 mortality policy that required it to pay benefits if her American Saddlebred gelding died or was euthanized because …