Toxic Metals and Animal Health

The potential toxicity of metals and their impact on animal health are rarely addressed in textbooks. Yet, not least due to increasing environmental concerns, the diagnosis and treatment of metal-related ailments in companionand grazing animals is starting to become an important aspect of daily practice for veterinarians and animal naturopaths. Furthermore, simply raising awareness of metal toxicity and animal health could lead to simple measures such as species-appropriate, individualized feeding and supplementation, saving animal owners considerable stress and expense.

Veterinarian and toxicologist Dr. Ramesh C. Gupta, Professor at the Department of Pharmacology and Toxicology at the University of Louisville School of Medicine, focuses on the pharmacokinetics and toxicokinetics of metals. In his writings, he emphasizes that the effects of toxic metals on animal health should be addressed more, because it is known that high levels of the following toxic metals affect animal fertility, such as:

• Cadmium: Ischemic necrosis of the testicle
• Chromium: Decreased testosterone; ↓ sperm count
• Lead: Decreased testosterone; ↓ sperm count; ↓ fertilization rates
• Mercury: Reduced sperm quality

Gupta emphasizes that lead and cadmium are ubiquitous heavy metals associated with both testicular toxicity and impaired fertility in a range of animal species.

Cadmium can impair the cellular metabolism of zinc, an essential trace element necessary for normal reproductive function. In addition to cadmium exposure, zinc deficiency may make individuals more susceptible to the toxic effects of cadmium (Akinloye et al., 2006). Pretreatment with zinc has been reported to reduce cadmium-induced Leydig cell cytotoxicity and neoplasia in male animals (Thomas, 1995). The primary function of Leydig cells is testosterone synthesis.

The ovaries appear to be less sensitive to the toxic effects of metals than the testes. However, cadmium seems to inhibit the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the ovaries (Hoyer, 2006).

Gold treatments in domestic animals can cause congenital malformations. In 1975, the American veterinarian Dr. Terry Durkes from Marion, Indiana, began treating hip dysplasia in dogs with gold implants. In Europe, starting around 1988, the Danish veterinarian Dr. Jens Klitsgaard from Aalborg used gold implants in dogs and cats. In 1994, Ralf Schweda from Sibbesse (Hildesheim) became the first German veterinarian to learn the therapy from him and introduce it in Germany. Unfortunately, the method is now widespread in domestic animals (especially dogs, cats, and horses) and has been used tens of thousands of times.

Platinum compounds are toxic and chemotherapy treatment with cisplatin C is reported to be embryotoxic or nephrotoxic and to cause malformations in unborn animals.

In addition, excessive cobalt exposure can potentially disrupt normal spermatogenesis, and severe cobalt poisoning can lead to testicular problems (Thomas, 1995). Chromium and vanadium have also been associated with adverse reproductive effects (Thomas and Thomas, 2001).

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