Yes, and many people don't get the quick death of a captive-bolt pistol to the forehead. Many people die in a hospital after years of suffering from gradual organ failure, dementia, cancer, or other terminal diseases.

Besides that, I don't think we know if cattle are aware that when their herdmates disappear that they are dying. Herd animals in the wild such as zebras and wildebeest witness their herdmates being killed by predatory cats on a daily basis, something I think would be far more traumatizing than just having them disappear on a truck. Maybe I'm wrong, though.