Diarrhea is one of the leading causes of death in neonatal beef and dairy calves.
Treatment recommendations for calves with diarrhea usually focus on giving calves fluid and electrolytes in the form of oral electrolyte solutions.
Severely dehydrated calves may require intravenous fluid therapy to correct their fluid deficits and electrolyte imbalances.
In some specific types of diarrhea, veterinarians may also recommend antibiotics and other therapies such as anti-inflammatory drugs.
The beneficial effects of zinc are still not completely understood, but it is suspected that zinc may play a role in protecting the intestinal lining and improving immunological response.
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A recent publication in the journal Preventive Veterinary Medicine describes the results of a clinical trial that looked at whether oral zinc supplementation might be beneficial to calves suffering from diarrhea.
The clinical trial was performed at a large California calf ranch, where 40,000 of the 70,000 Holstein dairy calves are of pre-weaning age.
Male Holstein calves were enrolled in the trial if they experienced a first episode of diarrhea between one and eight days of age. These calves were then randomized into three groups.
One group received a daily placebo treatment, which consisted of an oral electrolyte solution that was zinc free, while the other two groups received daily treatment of oral electrolyte solution, which was supplemented with either organic zinc or inorganic zinc.
The study’s authors were not aware of which treatment the calves were receiving during the trial.
Randomizing calves to the various treatments and “blinding” the investigators are key components in performing a clinical trial to prevent bias from affecting the results.
Liver biopsies and blood samples were collected from all calves at the end of the study period to measure copper and zinc levels.
Zinc is antagonistic to copper, and it was important to ensure that copper deficiencies weren’t being created by treating the diarrheic calves with zinc.
Zinc supplementation has been consistently shown to reduce mortality in infants, but there was no significant effect of the zinc treatment on mortality rates in the calves in this study.
Zinc supplementation of the calves did not create zinc toxicity and did not affect the copper levels in treated calves.
Many of the results were not statistically significant, but promising results were seen in calves treated with inorganic or organic zinc.
Calves treated with organic zinc gained weight during a diarrhea episode compared to calves that were treated with the placebo, which lost weight.
As well, calves treated with inorganic zinc were more likely to be cured of their diarrhea symptoms and tended to recover sooner than calves in the placebo group.
Calves treated with organic zinc that were infected with cryptosporidium, a common parasite that causes diarrhea in young calves, were also more likely to be cured at the end of the treatment period.
Many of these positive results were not statistically significant and may be simply due to chance, but they show enough promise that it should encourage researchers to conduct more studies to examine if oral electrolyte solutions for calves should be supplemented with higher levels of zinc.
Clinical trials such as this one are the gold standard for making scientific and data-based treatment recommendations.
These trials are difficult and expensive to carry out, but they provide veterinarians with the strongest evidence on which to base treatment recommendations. This trial may not have used a high enough dose of zinc supplementation or may have not had enough calves enrolled in the trial.
As a result, we are still left without a definitive answer on whether zinc supplementation will benefit calves with diarrhea. The results on weight changes and impacts on cryptosporidium are promising enough that it should result in further studies, which may provide a more definitive answer.
