Subsequent follow up postings seem to pretty well cover the idea that this wasn’t unusual at all given the weather conditions and actual numbers involved...
What Ann Barnhardt posted on her page was helpful and logic-driven also. Her background in cattle futures indicates that she's pretty knowledgeable on all things cattle-related. Article is the 2nd one down the page; title begins "Chart of Heat Stress in SW Kansas . . ."
Almost forgot: Her page is at www.barnhardt.biz