Calf scours are a challenging problem with young calves on the ground. High stocking density, moisture, and rearing younger calves in the same areas as older calves all contribute to the problem. Prior to about 3 days of age, calf illness is almost exclusively the result of non-infectious diseases, such as complications from the birthing process or issues related to nursing. After day three, the calf has had the opportunity to be exposed to bacteria and viruses and those agents have had time to set up shop.
Most folks believe that the bacteria E. coli is the primary cause of calf diarrhea. In fact, most cases of calf diarrhea are caused by a virus called rotavirus. E. coli can cause diarrhea up to about 5 days of age, but diarrhea in 1 to 2 week old calves occurs more commonly and nearly always involves rotavirus or its more severe compadre, coronavirus. It is important to recognize this, as most cases of calf scours do not require antibiotic therapy. Of course, some do, so I hope to show you a clear way to make decisions about what a calf with diarrhea needs and when.
Since we know that most cases of scours are viral, it’s important to understand how the viruses work. In the intestine, there are microscopic fingerlike projections (villi) that point towards the inside where feed and water pass.
Now look at your finger as though it were one of these villi. Most of the finger itself would be responsible for absorbing water and nutrients from milk and feed, while the part where it attaches to your hand is responsible for secreting substances in the other direction.
Rotavirus does its damage by lopping off the top third of the villus – like cutting your finger off at the first knuckle. When it does that to thousands of these tiny villi, the calf has now lost some ability to absorb water and nutrients. So the excess comes out in the feces. This results in a more watery stool, the calf becoming dehydrated, and losing important electrolytes.
For coronavirus, the “finger” is cut off at about the second knuckle. So, diarrhea and lack of absorption are even more severe and the diarrhea is often bloody. With this in mind, the number one principle of treating calf scours is to replace electrolytes and water.
Additionally, with erosion of the blood vessels and loss of the integrity of this inner lining of the intestine, bacteria can be absorbed into the bloodstream. For this reason, about 25 percent of calves with diarrhea will need antibiotics.
So how do we know which 25 percent it is? Two simple assessments will help you decide how to treat the calf on the farm and when to call the veterinarian. Can the calf stand? Can the calf suck your finger?
Whenever treatment is provided on the farm, your veterinarian should be contacted if the calf’s condition worsens at any time or if the calf does not improve in two to three days.
While treating a calf for scours, it is also important to limit spread of the infection by taking the following precautions:
- Separate the calf and dam from the rest of the herd.
- Immediately after use, disinfect all equipment used on the cow and calf. Wash the equipment first with soap and water to remove saliva, manure and other body fluids. Then soak it for 15 minutes in a chlorine solution by adding 1 ½ cups of bleach to 5 gallons of hot water and then rinse it well.
- Animal caretakers should wash hands well with soap and water after handling the calf and wear coveralls and overboots that can be disinfected. Treat the calf after doing chores on the rest of the herd in order to prevent tracking the virus back into the healthy herd.
Finally, calf scours should be considered a herd problem. If greater than 5 percent of calves develop scours, it’s certainly worth a conversation with your veterinarian so that a plan may be created to prevent illness the following calving season.