Which vitamins and minerals will help, which will hinder?

Essentially, cattle and sheep need at least 14 minerals and five vitamins in addition to energy and protein for good health and production.

Some are known as major elements, required in large amounts because they form a significant proportion of the body, such as calcium and phosphorus in bone, others are required in small or trace amounts because they are used in the formation of enzymes – powerful body catalysts that speed up essential processes.

Soil-Plant-Animal Interactions

Mineral deficiencies in grazing livestock are usually related to soil type, with problems found on light free-draining soils derived from sandstones and certain acid granitic soils. Heavier, clay soils tend to contain more minerals.

Trace element deficiencies may be simple, such as due to a lack of the element, in the case of cobalt and selenium, or complex as in the case of copper.

Excessive iron, sulphur or molybdenum in soil will lock up copper and reduce the animal’s ability to absorb and use copper. Applications of lime will reduce availability of copper to animals due to increased availability of molybdenum.

Varieties like perennial rye-grass have low concentrations of trace elements, whereas legumes and clover generally have higher levels. Grain, straw and root crops have low concentrations of many trace elements, barely sufficient for ruminants.

Trace element content is likely to decline as herbage matures, with values in hay and silage depending on stage of maturity on cutting.

There are seasonal changes in concentrations of trace elements and copper and manganese concentrations are lowest early in the season and highest late in summer.

Vitamin A and vitamin E levels are high in grass and forage crops, but low in roots, poor hay and prop-corn. Ruminants often depend on access to sunshine to ensure adequate levels of vitamin D.

Hay is a good source of vitamin D, but lush green grass and silage are poor and contain substances with anti-vitamin D effects.

The trace element requirements of herbage for growth are generally lower than those of grazing animals. In other words pasture growth may be satisfactory, but the animals can develop deficiency signs.

It can be concluded that trace element deficiency will most often occur where one or more of the background factors listed above apply.

Rations consisting of mainly grazed or conserved forage with perhaps whole mixes without mineral supplementation are the ones often associated with deficiency disease. Thus you can see why these conditions can become apparent in autumn after a long grazing period.

Age Variations

Finally, animals vary greatly in their requirement for essential minerals and vitamins. Young, rapidly growing animals have a higher requirement than mature or store animals. Requirement also depends on output.

Thus the heavily lactating dairy cow has a considerable demand for calcium because of the high calcium content in milk. Likewise the requirement for magnesium is greater during lactation than during a dry period.

Breed differences in the ability of sheep to extract copper from the diet are well recognised. Continental breeds such as Texels and their crosses are able to absorb more copper than Suffolks and Scottish Blackfaces. This can place a greater risk from copper poisoning on certain breeds.

Diagnosis

Specific diseases, such as swayback in lambs due to copper deficiency, iodine deficiency as the cause of abortions or the birth of weakly calves or lambs, can be attributed to vitamin deficiency.

More often the deficiency is apparent only through a failure to thrive or meet target weights or production levels. Other signs include malnutrition, parasitism and pneumonia.

Once these alternative diagnoses are eliminated, a tentative diagnosis may be made using local knowledge of when the problem is occurring, age group and species involved, soil and management factors.

However, it is worth remembering mineral deficiencies can predispose animals to other diseases, such as gastrointestinal parasitism.

Supplementation

The simplest and cheapest method of supplementing housed or grazing animals is to include a mineral vitamin mix in feed. If this is not possible, then consider injections, rumen boluses and oral dosing. Individual animals vary greatly in their intake of free access minerals.

Copper Poisoning

In recent years we have seen increases in copper poisoning incidents in both cattle and sheep, often due to over-supplementation with copper when it is not needed. Any sheep fed high copper foods, particularly those housed, are at risk.

Copper must not be added to sheep’s diets, as there is little that can be done to save poisoned animals. Supplementing with trace elements where they are not required is a waste of money and can place animal health at risk.