cattle; brucellosis; antagonists; livestock

Livestock production: Dealing with trace element antagonists

Question: The borehole water on my farm contains a lot of lime (calcium). Could this affect my animals’ health? What about inoculations?

Calcium is probably the best known antagonist to trace elements in Southern Africa and often occurs in borehole water.

  • Successful trace element supplementation is often hampered by significant quantities of antagonists in drinking water, pastures, feed and licks.
  • The level of antagonists in animals’ diets is not taken into consideration when trace element supplements in the form of licks and feeds are formulated.
  • It is extremely important that antagonists receive the same degree of attention as trace elements do, or more, when calculating and formulating the total diet of ruminants.
  • Too much could lead to a deficiency of trace elements and therefore to poorer production and breeding capacity.
  • Accurately estimating specific levels of antagonists will enable vets and animal experts to develop more efficient programme for supplementing trace elements.
  • The programme should be aimed at optimising trace element functions at important times in the production and breeding cycle of farm animals (drying up, lambing or calving, and mating).


The suppressive effect of antagonists on the efficiency with which trace elements are absorbed, and thus the efficiency with which their functions in ruminants (by means of enzymes) are expressed, is being understood more and more clearly.

Research conducted on trace elements has shown that antagonists are a greater problem than was perceived in the past.

The American Department of Agriculture has released data that show that supplementing copper and zinc, by means of licks, in areas where there are deficiencies in these elements, made almost no difference to the copper and zinc status of beef cattle.

The inability of lick supplementation to raise the copper and zinc status of beef cattle significantly was largely ascribed to the suppressive effects of antagonists.


In spite of the excessive quantities of calcium present in most borehole water, overabundant quantities of calcium are often found in licks and feeds, if calcium carbonate has to be included (because it is inexpensive).

  • Calcium levels that are too high depress the absorption of zinc, manganese, copper and selenium.
  • This leads to secondary deficiencies of these trace elements with resulting production and reproduction losses.
  • It is important to know that the old norm – that calcium be added at double the rate of phosphate content in licks and feeds – no longer applies.
  • Calcium should be supplemented only in terms of the needs of the animal.
  • The quantity of calcium in drinking water should also be taken into account.
  • Iron is, apparently, the least acknowledged trace element antagonist in Southern Africa.
  • It should not be added to feeds or licks, except in areas where it can definitely be said that there is an iron deficiency.
  • Apart from the fact that borehole water in Southern Africa is usually rich in iron, soil and natural grazing in the area usually also contain a fair amount of iron.
  • Iron is an antagonist of copper, zinc, manganese and cobalt.
  • Iron’s unfavourable effect on the absorption of copper, zinc and manganese has, as a consequence, a reduced reproductive efficiency.
  • Iron levels in borehole water should not be higher than 0.2 parts per million (ppm).
  • Borehole water contains up to 3 ppm, which is 15 times the acceptable level.
  • This leads to acute trace element deficiencies.
  • Sulphur is an antagonist of copper and selenium in particular, and often leads to lower conception rates and reduced calf and lamb percentages.
  • It is extremely important that the correct quantities of sulphur be included in licks and feed because ruminants need it for various functions.
  • Sulphur is also essential for the utilisation of non-protein nitrogen (NPN) by microbes in the rumen.
  • The problem is that the total ingestion of sulphur by ruminants is not always taken into account.
  • The total quantity of sulphur in borehole water, cultivated pastures (through fertilisers that contain sulphur), feed and licks that an animal ingests, can easily lead to a too high intake of sulphur, which in turn can lead to copper and selenium deficiencies.
  • Molybdenum is one of the less important trace element antagonists in Southern Africa.
  • It can, however, sometimes reduce the absorption of copper significantly and so lead to secondary copper deficiency.
  • It is well known that the ghanna bush of the Northern Cape Province in South Africa contains a lot of molybdenum, which can, at times, cause an acute copper deficiency in the area.
  • Because copper is deficient in some areas, and because it is suppressed by all 4 of the antagonists mentioned, Prof.
  • John Arthington of the University of Florida, USA, considers copper to be the most important mineral, after phosphate, for optimal production in beef cattle.
  • It is essential that attempts be made to ensure that the copper content of the lives remains above 125 ppm (dry matter) in beef cattle, with the aim of ensuring optimal production and breeding capacity.


According to Prof. Lee McDowell of the University of Florida, one of the greatest experts on mineral nutrition of our time, it is important that the goal of supplementing trace elements in ruminants should be to optimise trace element status and functions, not to prevent deficiencies.

The full genetic potential of the animal can then be realised.

He emphasises that subacute deficiencies in trace elements can occur even if no clinical symptoms of deficiency are present. These subacute deficiencies are the most expensive, and the most difficult, to manage because they often go unnoticed even though they can at times result in expensive increases in weight, poor breeding and poor production.

His most important conclusion, emanating from these statements, is that trace element “deficiencies” (non-optimal trace element status) are usually a combination of a series of factors in which antagonists generally play the biggest role.

The cause of “deficiency symptoms” (poor production and reproduction) is seldom of such a nature that it can be correctly understood and interpreted.


At farm level, an attempt should always be made to supplement trace elements effectively with licks and, at the same time, to restrict the concentration of antagonists.

It is also essential to administer, subcutaneously, to ruminants, an injectable trace element mixture containing significant quantities of the 4 most important trace elements for optimal resistance and breeding efficiency (zinc, manganese, selenium and copper) before calving or lambing, mating, and adapting to feedlots.

Follow-up injections before critical periods will contribute greatly to combatting the factors, especially antagonists, that lead to suboptimal trace element levels.

Also read:
Livestock production: Trace elements for ruminants
Livestock production: How to supplement trace elements correctly

  • This article was written by Drs. Willie Smith and Lourens Havenga and appears in Ask the vet: What cattle farmers should know (1), compiled by Dr. Faffa Malan.

Arthington, J., 2003: “Mineral antagonists may Influence Copper Deficiencies”. Feedstuffs, June 16, 2003, page 11.
McDowell, L. R., 2003: “Grazing Ruminants Require Free-choice Minerals”. Feedstuffs, November 17,2003, page 12.

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