Copper and Zinc Supplementation Can Be Complementary!

by Bob Sadler BVSc, MACVSc, PG Dip Forensic.

There seems to be an element of confusion surrounding the supplementation of livestock with copper and zinc at the same time, and the interactions that may occur.

In recent months a variety of articles have appeared in the rural press relating to zinc supplementation and the role zinc may play in animal health and production. This is not surprising given the severe facial eczema season we have just experienced and the increasing availability of zinc supplements or zinc treatments for facial eczema.

Zinc’s role in protecting against sporodesmin liver damage is now well recognised. Its protective value against other fungal toxins that can inhibit production, such as zearalenone, is less well established. However, treating cattle and sheep regularly with zinc, either orally or by other means, is now being recommended by a variety of advocates. The purported benefits that may be associated with such supplementation range from the rational to the ridiculous, depending on the integrity and credibility of whoever is promoting their particular form of zinc supplementation. Only products for orally administration, whether given daily or intended to achieve a sustained slow-release of zinc, have passed appropriate scrutiny for efficacy and safety.

But any benefit that oral zinc supplementation may offer, be it protection against facial eczema if used at high doses, or enhancement of health and production if supplemented consistently at lower dosages, draws concern about its interaction with copper. Copper deficiencies are common in New Zealand’s livestock, especially cattle,. Hence supplementation with a mineral that may antagonise copper uptake or utilisation and promote a secondary copper deficiency, is a valid concern. Well recognised antagonists to copper are molybdenum, sulphur, iron and dietary phytates. It is often stated that zinc is another antagonist to copper, or that it “strips the copper reserves” from an animal.

This often quoted detrimental effect of zinc on copper is frequently stated without qualification or other explanation. Certainly, there is good evidence that increasing dietary zinc concentrations can reduce copper retention in livestock; even help prevent copper toxicosis.¹ But the research that established this should not be taken out of context or applied to all forms or dosage rates of oral zinc.

Like copper, zinc comes in many different forms or salts, such as zinc oxide, zinc sulphate, zinc chelates, and zinc amino acid complexes. Each form of copper or zinc has different physico-chemical characteristics. These characteristics determine how the mineral is utilised and absorbed by the animal, its relative toxicity, and the potential for interaction with other minerals or chemicals in the body. The form and dosage rate of zinc or copper given orally, is an important consideration when discussing their interactions. It is not valid to state that “zinc strips copper reserves”, without qualification.

In fact, there is researched evidence that copper and zinc given together orally in appropriate forms and dosage rates, are complementary, with the zinc even facilitating copper uptake and retention.². Recent unpublished New Zealand trials have supported this premise. Further, a New Zealand study indicated that where sheep received high-dose sustained zinc oxide for facial eczema control over an 18 months period, there was little change in their liver copper content.³. It is not accurate to state unreservedly that oral zinc is incompatible with copper absorbtion.

The role zinc can play in helping the health and production of livestock in New Zealand is being increasingly recognised. The role of copper is well established. Both minerals are co-factors for biochemical systems involving the immune system and modulation of physiological and reproductive function. The body’s demands for both zinc and copper are increased when under stress, be this associated with infection, or the physical stresses of growth, pregnancy and lactation.

There is at last an eroding of the mentality that there is little value to any mineral supplementation unless a gross or marginal deficiency that responds measurably to treatment can first be demonstrated. Balancing trace mineral intake to optimise the health and performance of the particular herd or flock in question is sound sense. Especially under the ever varying nutritional circumstances and stressors that accompany New Zealand’s reliance on pastoral farming. But what may be nutritionally “optimal” for any particular herd or flock at a particular time is not something easily quantified. The conclusions made from much trace mineral research are often generalised inappropriately. Therein lies a danger and an opening for peddlers of “snake oil and “alternative” theories of dubious value.

The myth and legend that often surrounds trace mineral supplementation and its benefits should be balanced by accurate reporting of the findings and conclusions of any formal research or field experience. The findings of good trace mineral research should be made known so that its implications may be considered for the individual circumstance.

With this in mind, it should not become gospel that oral zinc has a negative impact on copper status, nor that supplementing them together is inappropriate or potentially dangerous. It all depends on the form and dosages of zinc and copper used.

References: ¹ Bremner et al, British J Nut.1976 .36:551-561

² Patterson et al, Proc. 4-State Applied Nutrition and Management Conf. and

Zinpro Tech. Symp. LaCrosse, WI. Aug 5 & 6, 1997.

³ Leo et al, Proc. NZ Soc. Animal Production, 1991. 51:173-177