No Need for Zinc Trace Element Supplementation

2 Dr E Berry

 Dr Elizabeth on her home farm with some Lleyn ewes

 Zinc content in forage is rarely deficient (less than one per cent of forages samples will have a deficiency)

and the amount of zinc in forage compared to the amount available from a bolus is significantly greater (often 100 times greater).

As most animals will get above 90% of the zinc required from forage the amount supplied in forage

is about 20 times the amount that an animal would get from a bolus.

For these and other reasons, there is no value in including zinc supplements in a bolus.

Whilst zinc is known to be critical for many enzyme factors, zinc deficiency is very rarely reported.

According to Teagasc* “Zn deficiency can be induced by high feed Ca levels, which block Zn absorption from the gut.

However primary deficiency of Zn is rare in ruminants.

There is a common enzyme copper-zinc superoxide dismutase which is important for a lot of reactions in the body.

This enzyme contains copper and copper deficiency is still commonly reported (as well as toxicity).

According to Dr Elizabeth Berry BVSC, PhD, MRCVS, Veterinary Director with Animax many elements interact

and this can mean that copper that should be available in the diet of animals becomes bound or unavailable.

So sometimes a zinc deficiency is really related to a copper deficiency.

It is important to monitor trace element levels in ruminants on a regular basis, in all situations, at least annually.

Bear in mind that changes to pasture, such as reseeding or liming, may change the availability of trace elements.

The weather can also affect availability – in wet seasons, animals ingest more soil than in dry years,

making cobalt more available, but copper less so.

However, there is little evidence to suggest a deficiency with pasture levels of 25 mg/kg dry matter. 

Typically pasture levels vary between 20-60 mg/kg dry matter depending on factors such as grass growth, season and soil type.

Some trace element bolus do contain zinc but it is important to establish a need

to give extra supplementation for zinc (and check copper status due to the common enzyme).  

For some trace element bolus, the amount of zinc is negligible and is unlikely to have an effect compared to the background level of zinc.

Animax is best known for their Allsure (ROI) & Tracesure (NI) range of leaching boluses which deliver a prolonged release of the key trace elements.

Copper, cobalt, iodine and selenium are the four trace elements which are essential for supplementation in low trace element diets in livestock.

The boluses leach known and optimum levels of these elements for up to six months.

Sadly one bolus manufacturing firm, in particular, is pushing zinc supplementation in their trace element bolus!

Flor Ryan, the Animax sheep specialist says that “farmers and animal health merchants should be aware

that putting a Zinc supplement in a bolus is usually a complete waste of money”.

Editors Notes

The Agriculture and Horticulture Development Board support a forage sample of 25 mg/kg DM being adequate – written by Nigel Kendal of Nottingham University.

Animax was founded in 1982 by a Scottish veterinarian Les Porter BVMS FRCVS, who recognised

that technological and scientific advancement that can increase yields and production,

optimise fertility and support animal health, would become crucial for farmers.

He worked in vet practices in Scotland and Kent before joining New Zealand’s Ministry of Agriculture in 1967 and

then the Invermay Research Station where he researched sheep diseases.

After more research work in India and Australia, he joined Bayer UK   in 1976 as their veterinary advisor

Animax is best known for their range of leaching boluses which deliver a prolonged release of the key trace elements.

Copper, cobalt, iodine and selenium are the four trace elements which are essential for supplementation in low trace element diets in livestock.

The boluses leach known and optimum levels of these elements for up to six months.

Individual animal demands for trace elements including zinc will vary with age and factors such as pregnancy and lactation.  

There are slightly higher demands for zinc at peak production in dairy cattle (around 50 mg/kg DM) but

these figures were calculated for high yielding (10,000 litres) large Holstein cattle. 

In addition, calcium can interact with zinc absorption, something that may occur in dairy cows in early lactation.