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Post-weaning brings on National Sick Calf Month
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Vet Report

Post-weaning brings on National Sick Calf Month

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Beef calves

Feeding both cows and calves a small amount of the supplement or weaning ration prior to weaning, in the weaning pen or pasture, can be used to help acclimate calves to both the feeds and the environment. 

Tri-State Neighbor Columnist

Dr. Lainie Kringen-Scholtz is Associate Veterinarian at Twin Lakes Animal Clinic in Madison, South Dakota.

We always joke/nervous laugh that October is “National Sick Calf Month” and depending on how pessimistic we feel, sometimes it’s “National Dead Calf Month.”

Calves getting sick after weaning is a fact of life no matter how “perfect” your program is. Below is what we are seeing in the field this month.

Histophilus somni

Formerly known as Haemophilus somnus, Histophilus somni is a gram-negative bacterium that inhabits the upper airway. It is most commonly found in feedlot calves between 6-12 months of age. Almost all cattle will be exposed to this pathogen at some point in their lives.

H. somni is an opportunistic pathogen, meaning that it can only infect calves with a compromised immune system which commonly occurs due to stress like weaning, bad weather, or coexisting viral infections.

Clinical signs vary greatly from neurologic disease, to heart inflammation, to respiratory signs.

Lainie Kringen-Scholtz

Lainie Kringen-Scholtz

Mycoplasma bovis

Mycoplasma bovis is a gram-negative bacterium that causes pneumonia, mastitis and arthritis in cattle. One of the hardest parts of treating cattle with M. bovis is that this bacterium does not have a cell wall, which makes it much more resistant to antibiotics.

Typically, M. bovis is found alongside all of the other pathogens but it can be a primary cause of pneumonia too.

Clinical signs include coughing and depression but they often keep an appetite. If it gets into the blood stream and subsequently into the joints, the cattle will be very lame and have joint swelling.

Mannheimia haemolytica

Mannheimia haemolytica is a gram-negative bacterium that was formerly known as Pasteurella haemolytica. It lives in the upper respiratory tract of healthy cattle. During stressful events when the immune system is compromised, the bacteria overgrows and causes disease.

The reason why M. haemolytica causes so much damage is because it makes a leukotoxin that causes excessive lung inflammation and tissue damage. As damage occurs and abscesses form in the lungs, the cattle become lethargic, have a high fever, and often times have a moist cough.

Sick lung

Lungs from a fat steer with Bovine Respiratory Disease complex.

Bovine Coronavirus

Bovine Coronavirus (BCoV) is found all over the world in healthy cattle but can cause mild respiratory disease in calves typically younger than 6 months. It can also cause diarrhea in baby calves.

BCoV most likely is not the primary cause of disease, but it is found alongside many of these bacteria from the lungs we have submitted.

The vaccinations available are designed to prevent the gastrointestinal form of this disease.

Why aren’t we finding many viruses in the lungs?

Most of the time, viruses are the primary pathogens for respiratory disease in cattle but at this time of year, the viruses have already done their dirty work and have allowed the bacteria to set in. The BCoV that is coming back on the samples that we have sent in may or may not be significant but we do know that it is not the primary cause of disease.


Even the most “perfectly” vaccinated calves can get sick. The immune system is extremely complicated and impacted by weather, nutrition, stress, past illnesses, etc.

We live in the gray area of life instead of the black and white. Nothing is perfect; the immune system, the vaccine, the calf as a biological system. All we can do is our best, pay attention and have a good relationship with your veterinarian to make the best choices for your cattle

Dr. Lainie Kringen-Scholtz is associate veterinarian at Twin Lakes Animal Clinic in Madison, South Dakota. 

This vet report is provided in conjunction with Twin Lakes Animal Clinic and Howard Animal Clinic. Questions? Send an email to Lainie Scholtz, DVM at, call 605-256-0123, or write 45305 SD Highway 34 Madison, SD 57042.

The Tri-State Neighbor Weekly Update

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Tri-State Neighbor Columnist

Dr. Lainie Kringen-Scholtz is Associate Veterinarian at Twin Lakes Animal Clinic in Madison, South Dakota.

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