It’s generally not the gut infection that causes scours that kills the calf, it’s dehydration. Regardless of the cause of scours (whether bacterial, viral, protozoal or something else), dehydration and the resultant acid-base imbalance is often what kills the calf.
Dehydration, the loss of electrolytes and decrease in pH in the blood (metabolic acidosis) are the three biggest problems. Rehydrating those calves is critical.” – Geoff Smith, DVM
Source: American Dairymen, August 6, 2021. Link. When a calf is about 5% dehydrated, we start to notice the calf will be dull and not quite as strong and perky. By about 12% dehydration the calf is close to death.
There’s a small window between 5% to 10-12% when he’s on death’s doorstep.” – George Barrington, DVM, PhD