A recent publication in the Journal of Veterinary Diagnostic Investigation provides important information about trace mineral and vitamin levels in calves from western Canadian cow-calf herds.
Dr. Cheryl Waldner and Dr. Barry Blakley from the University of Sask-atchewan’s Western College of Veterinary Medicine wrote the paper, which describes the findings of a large scale study carried out in cow-calf herds in Alberta and Saskatchewan.
Trace mineral and vitamin deficiencies contribute to a large number of diseases and conditions that might lead to abortions, stillbirths and neonatal death loss in cattle herds.
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Sending liver samples to a diagnostic lab is the best way to evaluate trace mineral and vitamin deficiencies. The liver stores many of the important minerals and vitamins, and samples from it provide the best indication of deficiencies.
In older animals, we can obtain liver samples at post mortem or occasionally by liver biopsy while they are alive. Liver biopsies are actually not difficult to do and are reasonably safe to perform in adult cattle.
However, liver samples from young calves are usually obtained only at the time of death during a post mortem examination.
This project was part of three larger studies, which were investigating risk factors for abortion and calf mortality in commercial cow-calf operations.
Local veterinarians carried out post mortem examinations on calves that died from abortion, stillbirth, or shortly after birth. Liver samples were submitted to WCVM from 501 calves.
Selenium levels in calves that were aborted or stillborn tended to be high in more than 97 percent of the samples. However, liver selenium concentrations were deficient in more than 30 percent of the calves that died after three days of age.
Vitamin E levels, which are often related to selenium, were shown to be higher in calves that were born alive than in calves that died at birth.
The study also examined copper levels, although copper metabolism in young calves does not mature until three to four days of age, which makes it difficult to evaluate liver copper levels.
However, bovine milk is low in copper, and so calves require some stores in the liver to meet their requirements while they are relying on milk as their primary nutritional source.
Almost 50 percent of the liver samples in this study would have been considered as less than adequate, which provided further evidence of significant copper deficiency levels in western Canadian cow-calf herds.
Vitamin A levels were also examined.
The liver contains 90 percent of the body’s vitamin A stores. Calves are born with relatively small amounts of vitamin A and get a large amount of their intake from colostrum.
A large proportion of the stillborn calves and calves that died shortly after birth had less than adequate vitamin A levels. This may be partly because many of them failed to suckle and receive adequate colostrum.
Carotene, which is found in green feed, is the major source for vitamin A in cattle. They build up vitamin A stores on pasture during summer, but these begin to deplete when they are fed stored feed.
Vitamin A is not stable in stored feed, and levels can be low in forage that is harvested during drought conditions.
The study found some evidence that herds fed a loose trace mineral mix during gestation tended to have higher vitamin A levels. Calves from heifers also tended to have higher levels, which might be because many producers use their best forage and feed when feeding heifers.
Producers need to continue to work with nutritionists and veterinarians to ensure their cattle have adequate trace mineral and vitamin levels, especially in cows during pregnancy and through early lactation.
