Yeah Ken-L-Ration was the standard for us too when I was a little kid. Came in case lots. We "understood" that when horses got old and died they got made into dog food, hoofs into wood glue. So we were told.....
The only thing more contentious then slaughtering horses for meat are the PMU farms.
Fortunately, last I heard they were falling out of fashion, not for obvious humane reasons, but because of the side effects of the hormone treatments on women.