Calf crop percentage is one of the most important production factors influencing the economics of the beef cow-calf farm.
This is usually defined as the percentage of cows exposed to the bull that raise a calf to weaning.
To achieve this, a cow must become pregnant, successfully carry the calf through to term, give birth to a live calf and raise it to weaning age.
Factors that can influence the calf crop percentage include reproductive management and calf losses through abortions, stillbirths and other mortalities.
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A research study recently published in theCanadian Veterinary Journalprovides an overview of the reasons for calf losses in western Canadian cow-calf herds.
Dr. Cheryl Waldner of the Western College of Veterinary Medicine followed almost 30,000 beef cows in 203 herds through an entire breeding and calving season.
During that period, the majority of abortions, stillbirths and dead calves on those farms were given a postmortem examination and tissues were submitted to the diagnostic lab for analysis.
The study gives a snapshot of the normal level of calf losses in western Canadian cow-calf herds.
During that breeding and calving season, 1.6 percent of the pregnant cows aborted, 2.6 percent of the calves were stillborn and four percent of the calves born alive died before reaching weaning age.
These numbers are similar to what has been seen in other North American studies and would suggest that more than eight percent of the calf crop is lost after the cow becomes pregnant.
A degenerative condition in the muscle tissues was one of the most common diagnoses in stillborn calves and those that died after birth. It is often associated with nutritional deficiencies, particularly selenium and Vitamin E, and is also commonly noticed in calves that die from starvation, exposure, infectious disease or calving problems.
Selenium deficiency has been associated with poor reproduction and the classical muscle degeneration in calves known as white muscle disease, which can result in sudden death. It may also cause impairment of the immune system and result in animals being more susceptible to other infectious diseases.
Many parts of Western Canada have soil that is deficient in selenium. As a result, the mineral is included in most trace mineral supplements fed to beef cattle.
The authors noted that all but four of the producers in the study reported providing some type of trace mineral supplement to their cows.
It would appear that this method of supplementation for selenium and Vitamin E may not be adequate to prevent problems in the fetus and newborn calf.
Other studies have previously demonstrated that free choice supplementation with selenium does not ensure adequate selenium in the cows and their offspring.
Selenium is available in injectable form for supplementing pregnant cows and newborn calves and should be considered under certain management conditions.
This research emphasizes the importance of trace vitamin and mineral supplementation in pregnant cows and perhaps will result in future studies that examine best practices for supplementing beef cattle.
John Campbell is head of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.
