NASHVILLE, Tenn. – When a cow starts to lose body condition or goes down, an accurate diagnosis could reveal a range of problems including Johne’s disease, bovine leukosis virus, malnutrition or a mineral deficiency.
“There are a lot of diseases that cause thinness in cows,” said John Maas, a veterinarian from the University of California, Davis.
“Once they start down that slippery slope, they keep going down,” he said at a session on animal disease at the National Cattlemen’s Beef Association convention in Nashville.
Johne’s disease, or mycobacterium paratuberculosis, is more commonly seen in dairy cattle. It has a long incubation period characterized by weight loss, diarrhea and thin body condition. The disease causes the intestine to thicken so that it cannot absorb nutrients. Diarrhea develops and the animal starts to waste away.
Read Also
Port’s project list omission decried
Grain farmers weren’t necessarily expecting the port of Vancouver to be on the list of recently-announced major projects, but had hoped for at least a mention.
Research is looking for a connection between Johne’s and Crohn’s disease, a chronic intestinal condition in humans.
Calves may pick up Johne’s from their mothers before they are born or shortly after birth. A cow’s condition may deteriorate after calving and it may infect more in the herd, which means blood or feces samples should be tested.
Manure is the main source of infection. It can get into soil and water, where it may survive for a year and be ingested by other animals. Studies suggest about a third of cows in later stages of the disease could transmit it through colostrum and milk.
An infected animal is the most common way that the disease is spread between herds.
Purebred producers should ask for a veterinary herd assessment, which could include testing a percentage of the animals. Commercial producers should find out if their seedstock suppliers have a program in place.
Don’t bring dairy cows onto the farm to act as nurse cows. Maas said infected cows that shed bacteria around calves are a good way to perpetuate the disease.
The cows can still go to slaughter but will not be worth much.
National Johne’s working groups have been formed in the United States and Canada to assess risk and work on education to keep the disease out of herds.
Alberta Agriculture says one-quarter of dairy farms have the disease, although the actual number of infected cows is low.
Projects are underway in Ontario and the western provinces to train veterinarians on risk assessments and provide best management recommendations regarding the disease.
Vaccines have been developed in the U.S., Europe and New Zealand but are not available in Canada because they interfere with subsequent tuberculosis tests.
Bovine leukosis virus, or leukemia, is another troublesome condition.
“This disease has not been associated with any human disease,” said Dan Givens of Auburn University.
The infection is usually unapparent but once infected, an animal is always infected.
It is the most common cause of malignant tumours in cattle. Probably 40 percent of cattle carry the virus, but only about one percent develop tumours and die.
Tumours can form in the lymph nodes, spinal cord, heart, uterus, kidneys, spleen, intestines and tissue behind the eyes, giving cattle a popeyed appearance. Carcasses of infected animals are condemned.
An infected animal could drop dead for no apparent reason.
There is no vaccine to control it so producers should try segregating infected animals from the uninfected herd with a fence, keeping a distance of about three metres between them. As well, producers should try to control biting insects like horseflies.
Don’t use the same equipment for both sets of animals.
Infected blood could be spread by biting insects, common needles or equipment such as dehorners or contaminated palpation sleeves. Sanitation is important.
“A good dish detergent kills the virus,” Givens said.
Foot rot and pinkeye are the two most prevalent problems in beef cow herds, said Jim Floyd of North Carolina State University.
Foot rot is a smelly bacterial infection that causes a painful inflammation with deep tissue invasion. Deep fissures may be seen in the claw and there may be mild lameness with an oil discharge at the skin and horn joins.
Bacteria invade through damaged skin when cattle have been standing in mud or other moist environments. Cattle could also develop foot trouble in a dry area such as a dry, stubbly pasture. Mild cases may respond to a drying agent such as five percent copper sulfate.
“Start with injectable antibiotics early,” Floyd said. Read the label and follow instructions to make sure it is suitable for foot rot. Foot baths can work but they become a source of infection after three or four cattle have walked through.
“There are other conditions that can cause acute foot infections in cattle,” he said, including mineral deficiencies such as inadequate selenium, copper or zinc.
“Cattle that are deficient will show these diseases more.”
Pinkeye is most often seen in summer and fall. Prevalence varies from year to year and up to 80 percent of a herd can be infected from this contagious condition. It is painful and causes squinting, tearing and a central lesion in the cornea. In extreme cases, ulcers may be seen in the eye leading to blindness.
The infection can be spread by face flies or people examining cattle.
“You can act as the Typhoid Mary going from one cow to another,” he said.
Producers should read medication labels because some formulations are not for pinkeye and some may require a veterinarian’s prescription. Besides administering medication, producers should practice good fly control and breed cattle for eyelid pigmentation.
A selenium deficiency can look like a parasite or other problems, Maas said.
“When an animal with selenium deficiency gets sick, it gets sicker than most,” he said.
It may lead to white muscle disease in calves, retained placenta and calves that fail to grow well. Plants do not require selenium to grow, and modern agronomic practices such as irrigation and increased fertilizer have exacerbated selenium deficiency in the soil.
