Ask the Vet

Weaned Calf Losing Weight

A reader wonders why one calf out of a whole group is losing weight and is sickly. With more than one possible answer, Dr. McMillan says it's time to call the vet. (DTN/Progressive Farmer File Photo by Becky Mills)


We have a small group of calves we weaned about two months ago. They've been wormed and vaccinated, and they are on hay and a little feed. One of them is losing weight and has diarrhea. The rest are fine so far. What do I need to do?


If you have a veterinarian who is familiar with your operation, give him or her a call and discuss this with them. If you do not have a veterinarian who knows you and your operation, I would suggest calling one and getting them to come out and look over your cattle and your operation.

Lately, I have had several similar cases where owners bring in a stool sample, and when we check it, the calves are heavily infected with worms, or worms and coccidia. This is a simple and economical test that is tremendously underutilized.

There are many reasons calves that have been dewormed can still have worms. A calf can be missed. Also, we see more resistance to some dewormers -- especially some of the generic pour-ons. Many times, when calves are weaned, they are turned into the same lot calves used in the recent past, and the environment is heavily contaminated with parasite eggs and oocytes. These areas often get muddy, and feed bunks, troughs or pans become contaminated with mud and manure. Clean pastures or lots, and improved sanitation, helps prevent reinfections.

Nutrition is also very important. As I have noted before, calves must have a ration that meets their energy, protein and mineral needs. Healthy cattle are much more resistant to all diseases.

Another disease that should be considered in cases like this is persistent infection with bovine virus diarrhea or BVD-PI. These calves are infected during pregnancy and accept the virus as "normal." Many of these calves are smaller and sickly, but not always. All BVD-PI calves shed massive numbers of viruses continuously, so they are a threat to other calves in the herd. This condition can be controlled with testing and vaccinations.

The only way to know for sure what the problem is, is by getting a veterinarian involved. Find out what is happening in your herd, and then develop an ongoing herd health program to keep your operation and your animals healthy and profitable.


Write Dr. Ken McMillan at Ask The Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email


Please contact your veterinarian with questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.