Bad luck. Hot and humid weather is a nightmare for livestock, far worse than cold (unless it's stock caught in heavy snow). I have revived a ewe that died during shearing - she collapsed on her side and I cupped the heels of my hands together and pushed into her chest just below the brisket, roughly where I judged her heart to be, as for human CPR. After about a minute (and much to both my and the shearer's astonishment) the nerve above her eyelid began to flicker, I carried on and after another minute she took a shallow breath. Twenty minutes later she was back in the field and suckling her lamb. She went to cull after weaning, though.