These are usually caused by the following bacteria, viruses and parasites:
Rotavirus
Coronavirus
E. Coli (bacteria)
Crypto (parasite)
And nutritional scours
CALVES DIE FROM DEHYDRATION IN MOST CASES HERE
E. coli:
Can occur from 0-4 days of age
Often you will see weak and poorly suckling signs before death
Death is common
Scours are sometimes present but not always and don't involve blood
If present it is watery and yellow/white
You are more likely to find low temperatures below 38
E. coli link including treatment
Rotavirus:
Usually around 4-14 days of age
Yellow watery scours
NO BLOOD
Mild depression and reduced milk intake
Dehydration builds slowly
Normal temperature
Coronavirus:
Usually around 4-30 days of age so overlaps with Rotavirus
Yellow watery scours, sometimes mucus
Rarely blood
Mild depression and reduced milk intake
Dehydration builds slowly
Normal temperature
Crypto:
Usually from 1-4 weeks of age
Profuse watery yellow scour
Strong smelling
NO BLOOD Mild depression
Severe dehydration
Multiple mixed infections of the above can occur.
Nutritional Scours:
Usually from over feeding
Or individual gorging
They usually remove themselves from feeding and come right on their own.
Mark with paint and check in 24 hours.
If they don't self cure use
REMEMBER CALVES MAINLY DIE FROM DEHYDRATION
Supportive therapy:
Don't stop feeding milk
Feed electrolytes morning and afternoon
Feed milk at lunchtime (don't mix)
Leave electrolytes ad lib if needed
Give non steroidals like oral Meloxicare
The electrolyte program should run for two days.