It is certainly sad to see that kind of suffering and death. My thoughts on how to mitigate the situation is neither cheap nor easy. I would look at the solutions as broken into long term achievement and shorter term. In the longer term I think producers need to utilize cattle genetics from countries that traditionally are hot like India, and east central Africa, perhaps Mexico and Brazil. They be giving up some growth and quality, but the new genetics would certainly be more valuable than dead animals. Ranchers may need to consider providing shade as heat shelter, similar to how they provide for cold shelter in the winter. Also provide water sources close enough to the grazing areas so the animals do not have to travel long distance to drink. And even more radical, would be to acquire land farther north to graze in the summer, and retain land in the southern plains for winter grazing. Maybe they could negotiate a deal with northern producers to provide winter grazing for both parties, and the northern producers could provide summer grazing for both. Transportation costs would be enormous of course.
It depends on the insurance source as to whether the losses are covered. Most indemnity payments from FSA, would require that a disaster designation be approved for that county or adjacent county. Then the payments would only cover a portion of the losses. And often the payments are delayed for some time after the losses occur. Livestock insured under the crop insurance division of USDA have different rules and are based on the level of coverage selected.