Smallholder Summer Update: Trace Element Supplementation at Grass

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Most smallholders raise their animals – sheep, cattle, llamas, alpacas, goats; any grazing or browsing stock – from grass. However, not all pasture is the same, and trace element deficiencies can easily build up, especially if any additional forage is grown in the same geographical area (as it commonly is). In this article, our farm vet Morven looks at trace elements in livestock, and the need for supplementation at grass.

What are trace elements?

Trace elements are minerals that are required in relatively small quantities, in order to support livestock growth, pregnancy and productivity. In the UK, the main trace elements to consider are:

Copper (Cu)

Cobalt (Co)

Selenium (Se)

Iodine (I)

Zinc (Zn) and manganese (Mn) may need to be considered in some species, and sulphur (S) and molybdenum (Mo) can come into play due to their interactions with copper.

Supply and demand

Trace element requirements vary with age and level of production. Young growing animals and those that are pregnant or lactating (producing milk) have the highest requirements.

Availability of each trace element varies due to factors such as soil type, pH, drainage, plant species, and fertiliser use. Higher trace element concentrations are found in poorly drained pastures, clay soils, and in herb and weed types of plants. Lower levels of trace elements are typically associated with freely draining ground, sandy soils, rapidly growing grasses, and recent fertiliser application.

So, what happens if livestock do not get enough of these trace elements?

Trace Element Deficiencies

Trace element (TE) deficiencies tend to develop slowly and cause poor productivity or ill-thrift. Gut parasites and low dietary energy supply will cause similar signs so, if you suspect ill thrift or reduced productivity, get in touch with your vet to make a plan for investigation.

Copper (Cu)

Deficiency during pregnancy can cause Swayback in newborn lambs. Affected lambs may be stillborn or have characteristic hind leg weakness due to abnormalities of the brain and spinal cord. This is not curable – so prevention is key.

Deficiency in growing lambs can cause poor growth, scour (diarrhoea) and poor fleece quality, described as steely wool where the fleece loses its crimp.

In young cattle, poor growth rates may be seen as well as grey/brown discolouration of the coat around the ears and eyes, causing a “spectacled” appearance. The coat may also be thin and dry, and some animals may be lame due to bone growth disturbances.

Copper deficiency has been linked to poor or delayed fertility in heifers although this relates more to high intakes of molybdenum, which causes a secondary copper deficiency by reducing absorption of copper from the diet.

Molybdenum in high concentrations can similarly cause secondary copper deficiency in llamas and alpacas.

In goats, copper deficiency may cause similar signs to that of other ruminants (i.e. cattle and sheep). Goats have different copper requirements than sheep however, so may become deficient if fed sheep feed.

In all species, care must be taken when supplementing with copper not to over supply as this can lead to copper toxicity.

Cobalt (Co)

Cobalt deficiency, sometimes called cobalt pine, may occur alone or in combination with parasitic gastroenteritis (PGE) i.e. worms, which causes diarrhoea, further reducing absorption of cobalt from the diet.

Young weaned lambs at grass are most susceptible and symptoms include poor quality open fleece, poor body condition (despite appropriate nutrition), lambs small in size, reduced appetite, tear staining on the face, lethargy and eventually pale membranes around the eyes due to anaemia (low red blood cell count).

Additionally, young sheep may not respond well to vaccinations and therefore are susceptible to clostridial disease and Pasteurella pneumonia. In severe cases, neurological (nervous system) signs such as head pressing and aimless wandering may occur.

Cattle are much less commonly affected by cobalt deficiency than sheep although youngstock can show poor appetite, thin coat of poor quality, anaemia and poor growth rates.

Adult cattle and sheep are rarely affected by cobalt deficiency themselves but deficiency during pregnancy can result in reduced viability of newborn calves or lambs.

Selenium (Se)

Deficiency in selenium during pregnancy may cause newborns to be weak and unable to suckle. Growing lambs (2-6 weeks old) and calves (1-4 months of age) may show a sudden stiffness followed by an inability to stand. This is known as white muscle disease and occurs in animals that are otherwise bright with normal appetite.

Early pregnancy losses can occur in both sheep and cattle, leading to low scanning percentages with a high number of barren (empty) ewes or generally “poor fertility” in cattle. A higher incidence of retained placentas may be seen too but other causes exist for all these symptoms so speak to your vet if you have concerns.

Goats may be affected by selenium deficiency too, with muscular disorders, poor fertility, and retained placentas.

Iodine (I)

Iodine deficiency in sheep, goats and cattle during pregnancy can cause low scanning rates, late pregnancy abortions, stillbirths or the birth of live but weak lambs, kids or calves. Typically, the thyroid gland in the neck of newborns is enlarged. This is known as goitre.

Care must also be taken not to over supplement iodine, particularly to late pregnancy ewes, as this can cause pregnancy losses.

Zinc (Zn)

Zinc deficiency may be seen as it causes skin disease, lameness or reduced fertility in goats, cattle and sheep although this occurs less commonly than other trace element deficiencies.

So, which one is the problem?

Although telltale signs such as swayback or goitre can indicate specific deficiencies, many other symptoms are quite vague. Poor performance, reduced growth rates or disappointing fertility can have many other causes and supplementing trace elements where it is not necessary to do so would be, at best, expensive and in some cases harmful due to toxicity.

So how can we determine whether trace element supplementation is required and which elements are needed?

Testing for deficiency

As previously mentioned, some deficiencies cause specific signs such as enlarged thyroid gland (goitre) in newborns with iodine deficiency, swayback in young lambs with copper deficiency or stiff young lambs or calves with white muscle disease of selenium deficiency. If you suspect any of these conditions, contact your vet for advice on how to proceed. In such cases there are often losses by way of stillbirths or deaths of neonatal animals and post mortem examination of these individuals can be very useful to confirm the diagnosis.

In situation with less specific signs, for example poor scanning rates in ewes or poor growth rates in youngstock, it is important to work with your vet to develop a step-by-step approach to investigation which takes account of the type and age of animals involved, current practices regarding nutrition, vaccination, breeding and parasite control, and also the time of year. For example;

Low pregnancy rate in ewes in February may be due to infectious disease, poor ram/tup performance, inadequate nutrition, parasitic disease, or trace element (TE) deficiency. Blood testing ewes at this stage may give misleading results as low TE levels at mating time 3 months earlier, may be normal by scanning time due to different feeding or forage sources in the interim period.

Poor performance in youngstock may well relate to parasitic disease for example a high roundworm burden or coccidiosis, but TE deficiencies, particularly of Cobalt, can occur alongside these parasitic diseases too.

Additionally, assessing the need for trace element supplementation need not wait for a problem to occur! As the saying goes, prevention is better than cure, and understanding the TE situation on your holding can allow preventative steps to be taken.

This may involve blood sampling groups of livestock, liver tissue analysis (from post mortems or at the abattoir), forage analysis, soil sampling, water supply analysis or, most likely, a combination of these approaches depending on the holding. There is of course cost involved in all testing and results must be interpreted carefully and within the context of the individual livestock holding, so contact your vet to discuss the most effective approach for your system.

Supplementing Trace Elements

In housed animals or those receiving additional feeding outside, TE supplementation can be achieved easily and effectively by adding an appropriate mineral mix to the feed, either as a powder or as a mineralised compound feed.

In grazing animals who are not additionally fed, the method of supplementation will depend on the category of livestock involved and the TE required, as well as cost and handling considerations.

Free access minerals in the form of licks or blocks

These are easy to offer but very variable in terms of intake. The idea that individuals will “take what they need” is unproven and more likely some animals will remain deficient whilst others are oversupplied. These licks or buckets are potentially costly too and may attract wildlife such as deer and badgers.

Drenches and injections ensure each animal receives the required dose

However, frequent handling may be required. This may be most appropriate for young lambs for example where they are regularly handled for weighing or worming anyway and supplementation is only required in the relatively short term, from weaning until finishing.

Slow-release boluses are often more appropriate for older animals

Even where supplementation is required, frequent handling can be avoided. These boluses are delivered to the back of the throat using a special applicator gun, swallowed down into the stomach then the TE’s are slowly released over usually a 5-6 month period. Combination boluses are available where supplementation of more than one TE is required.

Bolus or drenching gun injuries to animals can be avoided by using good restraint, appropriate technique and care. Speak to your vet who will be happy to advise or demonstrate the techniques when you are starting out.

To reduce the need for supplementation of individual animals, consideration must be given to the pasture.

Top dressing of pasture for example with cobalt salts can be effective at raising long term TE levels, however cost must be considered as well as short term supplementation required in the meantime.

Promoting greater plant diversity and clover growth can also reduce the need for TE supplementation.

Examples of supplementation

Cobalt

Oral drenching every 3-4 weeks may be appropriate to maintain performance in lambs due to go fat in the coming month or two.

Ewe lambs to be retained for breeding could receive an injection of B12 (the vitamin that cobalt produces) from 3 weeks of age, or a cobalt bolus once they reach 20kg in weight. Each aims to give around 6 months supplementation from a single dose.

Clinically affected animals require weekly vitamin B12 injections to correct the deficiency, followed by longer term supplementation.

Treating pasture is typically more costly per animal than individual supplementation in the UK.

Selenium

In calves (or lambs) with white muscle disease, treatment is with selenium injections into the muscle.

In older cattle, boluses or injections under the skin may supplement selenium for 6-12 months (depending on product).

Adult sheep may be dosed orally before mating or supplemented through feed in the lead up to lambing.

Care must be taken when supplementing lambs as overdose can cause toxicity. Treating pasture can have the same toxic effect so is rarely carried out.

Iodine

Oral dosing may give short term supplementation but boluses containing iodine (often in combination with other TE’s) can provide up to 6 months’ supply.

Copper

Treatment of swayback in lambs is not possible as copper deficiency has already led to malformations of the brain and spinal cord. Prevention is usually through slow-release boluses of copper needles given to mid pregnancy ewes. An injection is also available for sheep, given 2.5 months before lambing and this may be particularly appropriate where copper deficiency has been identified as occurring due to high molybdenum levels (molybdenum reduces copper absorption).

In cattle, supplementation is via feed or boluses, with the best solution depending on the individual farm situation. Copper injection is not licensed in cattle in the UK.

In sheep there is considerable breed variation in the ability to absorb copper. Texels, Suffolks, North Ronaldsay sheep and other rare breeds are very efficient at absorbing copper. They are therefore unlikely to be deficient but susceptible to toxicity. Scottish Blackface sheep and breeds such as Cheviots are less efficient at absorbing copper therefore may be deficient but unlikely to experience toxicity.

Measure, Manage, Monitor

Whether you have health or production concerns for your livestock at the moment, or just want to be proactive to avoid trace element issues, the aim is to measure, manage and monitor.

Measure – investigate ongoing issues or identify existing deficiencies accurately.

Manage – plan practical, cost-effective measure for treatment and prevention.

Monitor – response to supplementation will confirm the diagnosis of a deficiency and if can support the need for ongoing supplementation in situations where clear clinical signs of deficiency have not been present.

There can be many other factors at play including infectious diseases, parasite burdens and nutritional imbalances, and no two farm holdings are the same. The best outcomes will be achieved by working in partnership with your vet who will be happy to advise you further.

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