Vitamin E/Selenium Deficiency
Selenium deficiencies in soils can have devastating effects on livestock. Some areas of the United States, including the north-east, are considered low in selenium. Areas of the south-west of Western Australia are also known to be selenium deficient. Soil which has less than 0.5mg Se/kg of soil is regarded as deficient.
Selenium deficiency may occur because of:
- low levels of the substance in soils
- low absorption of the mineral into pastures, or
- antagonism with substances such as sulphates.
Selenium deficiencies have the potential to severely affect the health of, particularly, sheep and goats resulting in loss of animals (and income) for the producer.
White Muscle Disease
There is a wide range of disorders associated with low or marginal levels of selenium. One of the most common is White Muscle Disease (WMD). The disease gets its name from the pale coloured muscles of deceased animals.
White Muscle Disease manifests as severe muscle wasting and weakness. It is most common in newborn or fast growing animals. Lambs and kids are commonly affected. The disease affects both skeletal and cardiac muscles. If the skeletal muscles are affected, lambs/kids may suffer mild stiffness, obvious pain upon walking or even an inability to stand. The gait may be stiff and the body hunched. While the appetite may be normal, the affected animal becomes too weak to nurse. Newborns may be born weak and unable to suckle.
If the cardiac muscles are affected, the symptoms are similar to pneumonia: difficulty breathing, fever and frothy discharge from the nostrils. Heart and respiration rates are elevated and may be irregular.
Because of the wasting of muscles involved with cardiac and respiratory function, sudden death may result. General weakness and malaise, poor immune systems and a greater tendency to infections are commonplace.
Selenium and Vitamin E
Low levels of selenium may occur in tandem with Vitamin E deficiencies. Vitamin E deficiency is not dependent on soil type but more closely reflects the quality of grazing. Most grazing animals consume sufficient amounts of vitamin E. However, silage, cereal grains, dry hay, and root crops tend to lead to vitamin E deficiencies. This may occur when stock have no green feed or are on diets high in grain (especially lupin) or fat. Prolonged storage of foodstuffs can result in low vitamin E levels.
Vitamin E and selenium do not have similar functions but they are complementary. If a diet is low in Vitamin E, there is an increased need for selenium and vice versa. There is, however, limits to the effects each has on the other. Adequate dietary selenium usually protects an animal from vitamin E deficiency. If pregnant animals have sufficient levels of selenium, the young are rarely affected. The mineral is transferred through the placenta to the embryo and is also present in the colostrum.
Animals deficient in selenium and vitamin E may have a number of reproductive problems. They also have symptoms of ill-thrift. Reduced weight gain, lowered milk production, lower conception rates, reduced semen quality, foetal reabsorption, retention of the placenta, stillbirths and abortions are all observed. Foals may be born weak. Lambs have a poor rate of growth. Sheep have low fleece yields and increased periodontal disease.
Different treatment methods will suit different owners. Selenium can be added to rations or given as drenches, pellets or injections. It is also available as a 'pour-on' and can be added to the soil as a fertiliser.
Injections are fast-working but need to be repeated or followed up in some way. Pellets can be given to cows with the effect being passed on to calves for 4-6 months. Calves under 12 weeks cannot be pelleted. Selenium-enriched salt licks can be used but intake will be variable. Licks need to have 40mg selenium per kilo of salt. Fertilisers are effective only if pastures are growing well. Even then, benefits to stock will not be immediate. Vitamin E is available in premixes, green feed and by injection. For horses, selenium is available in pellets, by injection and drenching.
If your stock are not thriving and seem generally 'wasting' away, have their selenium levels checked. The results may be surprising.