Disease management helps reduce pregnancy losses

Pregnancy loss is a natural process, but good herd health and nutrition management can keep it to a minimum.

Three percent of cows lose their pregnancy for a myriad of reasons, said veterinarian Steve Hendrick of Coaldale, Alta., who works with cow-calf and feedlot clients.

“I recognize that wrecks can still happen even in the best managed herds,” he said during a recent webinar sponsored by the Beef Cattle Research Council.

“As technology improves in ultrasound … it has allowed us to detect pregnancy earlier. In doing so, we realize how much more common pregnancy loss really is. It is difficult to diagnose. The insult often happens before we actually see some of the signs that show up.”

The 2015 Western Canadian cow-calf survey reported an average pregnancy rate of 93 percent and an actual calving rate of 90 percent, which means about three percent are lost.

Questions need to be asked if a number of cows are open during pregnancy checking time.

Producers should check the bulls that were used and find out whether the affected cows had a common sire or dam.

A pregnancy can end at less than a month of age, and the fetus may not be found or it may have been absorbed.

If a cow was pregnant and then starts cycling again, check for pyometra, which is pus from the uterus. If the cow lost the pregnancy early, debris could be left behind.

Losses may be attributed to genetic or developmental defects, infection from bacteria, viruses, protozoa, stress during breeding or poor nutrition.

A fetus’s age can be estimated if it is found:

  • two months pregnancy — mouse size
  • three months — rat size
  • four months — small cat size
  • five months — large cat
  • six months — small dog with hair starting to show
  • seven months — fine hair growth
  • eight months — hair coat complete and teeth slightly erupted
  • nine months — incisors erupted

Fully developed but stillborn calves may happen more often in heifers than cows. The calf may have been too large, the mother was too thin or overweight or calving difficulties or malpresentations may have occurred.

Many producers write off a few losses, but they should talk with their herd veterinarian if more abortions occurred than normal.

Be as specific as possible when describing pasture management, feed, water and stage of pregnancy.

If possible, collect the fetus, placenta and blood samples from cows that aborted. Place the material in double heavy-duty plastic bags, pack in ice and do not freeze.

The fetus may have frozen outside if the abortion occurred in the winter, but try and get the package to the vet or laboratory as soon as possible.

A diagnosis is found in about one out of three cases. Half the time the cause is related to a bacterial infection such as campylobacter, vibrio, leptospirosis, listeriosis, brucellosis, salmonella, histophilosis or treperella.

One-third of the cases are a viral infection such as bovine viral disease or infectious bovine rhinotracheitis.

The cattle may also have been infected with protozoa such as trichomoniasis, neosporosis or sarcocystis.

Non-infectious causes could be mouldy feed that leads to contamination such as Aspergillus fungus or mycotoxins such as ergot and fusarium.

Nitrates in forages could be linked to pregnancy losses, so feed should be checked.

Some cows could abort if they ate ponderosa pine needles during cold weather when they have taken shelter around trees.

Genetic abnormalities and rough handling combined with other stressors may also be at fault.

A western Canadian study in 2000-05 examined fetuses lost because of abortion. More than one-third were undetermined. In other cases, thyroid gland lesions, pneumonia, congenital abnormality, placentitis and abnormal heart muscles were detected.

IBR and BVD infections made up less than three percent of cases.

Stillbirths from the same study found:

  • 40 percent were dystocia or malpresentation
  • 21.6 percent undetermined
  • 8.9 percent thyroid gland lesions
  • 7.1 percent myocardial necrosis
  • skeletal muscle myopathy or abnormal muscle appearance

Preventing pregnancy loss starts with good management such as well balanced diets, vaccination and low stress handling.

“It is surprising how much variability occurs in our forage from year to year and season to season,” Hendrick said.

Get feed tested to avoid myco-toxins such as fusarium.

Monitor body condition scores because this can affect the next calving season.

Check their body condition at pregnancy checking time so they can be sorted and fed accordingly.

Include minerals in the rations, especially in the last trimester when the fetus is growing rapidly, and extend it to lactation. Many people provide minerals in lick tubs but are often unsure if cows are getting enough.

Vaccination against BVD and scours is critical.

“A vaccination program is your insurance policy from a health standpoint. It is not 100 percent,” said Hendrick.

“Work with your veterinarian who knows your herd and risks in your area to design a proper protocol for your herd.”

A 2015 study summarized a number of trials and found a five percent increase in pregnancy rates and a 45 percent decrease in abortions when BVD vaccinations were used. Of those calves born alive, there was an 85 percent decrease in fetal infection rate.

Hendrick believes a modified live vaccine provides better protection than killed vaccines, but producers should consult with the herd veterinarian. Check the labels to see if they are safe to give to pregnant cows.

He recommended giving replacement heifers three doses of scours vaccine before breeding. Branding, weaning and prebreeding times may be most convenient.

Practice biosecurity and consider screening bulls for trichomoniasis and vibrio, especially if using community pastures.

Culling or isolation of affected cattle or groups lowers the risk of disease transmission.

Farm dogs can be tested because they can pass neosporosis in their feces.

A calculator is available on the beef cattle research council website at www.beefresearch.ca/research/body-condition-scoring.cfm to calculate body condition scores, feed requirements and what it might cost to maintain or bring a cow up to the ideal weight to support a pregnancy and a calf.

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