Selenium is an anti-oxidant which helps destroy toxic molecules produced during normal metabolism in ruminants. It is necessary for growth and fertility in animals.
Deficiency causes significant productivity losses, and can lead to White Muscle Disease (WMD), infertility, decreased milk production, and ill thrift.
Selenium deficiency is a reasonably widespread problem in New Zealand, particularly in the South Island and central North Island.
Selenium does not have a high safety margin, and excess supplementation can cause toxicity. Supplementation should only be done under recommendation from a veterinarian.
Cobalt is used by the micro-organisms in the rumen to produce vitamin B12.
Vitamin B12 is essential for normal ruminant metabolism, in particular the production of glucose.
Deficiency causes decreased growth and appetite, poor wool production and anaemia in severe cases.
Rapidly-growing sheep, particularly weaned lambs have the highest demands, and in marginally deficient regions will benefit from vitamin B12 supplementation. In more severely affected areas other classes of stock may also be affected, these include:
Copper is an essential trace element required for a large number of processes within the body.
Deficiency can lead to:
Swayback (enzootic ataxia); lambs are either born unable to stand or have incoordination of the hindlimbs or develop these signs within a few weeks of birth.
Bone fragility (osteoporosis); this is often seen as an increase in bone fractures occurring after docking or other handling events during autumn and winter in lambs.
Wool abnormalities; can cause loss of pigment in black sheep or loss of wool crimp.
Impaired reproductive performance; may cause increased foetal loss and decreased lamb survival in ewes and decreased semen quality in rams.
Copper deficiency can result from a lack of copper in the soil (primary copper deficiency) or more commonly as a result of interference by other elements (secondary copper deficiency) either at the soil level (Increased pH and molybdenum will decrease copper availability) or within the rumen (molybdenum and sulphur form thiomolybdates which will bind up copper. Iron and zinc will also decrease copper availability or utilisation).
Copper in excess can be toxic, therefore supplementation should be undertaken with careful monitoring.
Iodine is stored in the thyroid gland and is involved in the production of thyroid hormones.
Thyroid hormones are important for energy metabolism and the production of cell proteins. In the foetus they are essential for the development of the brain, lungs heart and wool follicles.
Lack of Iodine leads to:
Goitre (enlarged thyroid glands) in lambs.
Increased lamb wastage.
Lambs born with little or no wool and pink skin in very severe cases.
Goitre can be due to lack of Iodine in the soil particularly in very wet area but most are associated with the presence of goitrogens in feed (particularly brassica crops), which interfere with the uptake of Iodine.