Forages grown in the Pacific Northwest may be deficient in the trace element selenium. Selenium is a trace element that is essential in the diets of all farm animals. Unfortunately, the soils in the Pacific Northwest contain little to no selenium. Generally, if the soil is selenium deficient, the forages grown on that soil will be deficient. Therefore, care must be taken to ensure adequate selenium intake by livestock that Ware fed hay and grains grown in the Pacific Northwest. Many supplements and mineral blocks that contain selenium are available for horses, cattle, sheep and goats. Be aware, however, that too much selenium is toxic.
The importance of adequate selenium nutrition for gestating ewes to prevent white muscle disease in lambs was reported almost 40 years ago (1). White muscle disease is degenerative muscle disease that occurs in livestock species and is most commonly seen in calves, lambs, kids and foals. Feeding the cow, ewe, doe or mare a diet that contains adequate selenium and vitamin E will prevent white muscle disease in their young. However, white muscle disease is not the only health problem caused by diets that are deficient in selenium. Lambs of ewes fed selenium deficient diets during pregnancy have impaired absorption of immunoglobulins from colostrum. Immunoglobulins are antibodies produced by immune cells that recognize and neutralize foreign material such as viruses and bacteria. Lambs that cannot absorb immunoglobulins from colostrum have impaired immune systems and are more likely to get sick and even die. In addition, selenium is a component of many enzymes that are important in cellular defense mechanisms, once again highlighting the importance of adequate selenium nutrition.
Dairy and beef cattle fed diets with adequate selenium levels have lower incidence of retained fetal membranes after calving. Incidence and severity of mastitis is decreased, and milk somatic cell counts are lower in cattle that have been fed selenium-supplemented diets. Calf mortality is also decreased when cows are fed diets with adequate selenium content during gestation (2). Low intakes of selenium also alter thyroxine metabolism in ewes and their lambs. Thyroxine is the primary hormone produced by the thyroid gland and it plays a major role in regulating many metabolic functions in all animals. Thyroxine is important for normal development including development of wool follicles in sheep. Furthermore, adequate selenium nutrition is important for reproductive efficiency in both male and female animals. Ewes given an oral drench of selenium prior to mating generally have lower embryonic mortality and hence, more multiple births, while rams injected with selenium have fewer abnormal sperm (3). Evidence also exists that semen quality is improved in stallions fed diets with supplemental selenium and other antioxidants (4).
The only way to positively determine the selenium content of your hay is to have it analyzed by a laboratory. Selenium can be added to the diet by providing livestock with selenium-supplemented mineral blocks or grains. However, make sure that you are not providing too much selenium, for example, from several different sources.
Have you found a good way to supplement selenium for your animals? Share with us in the comment section.
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References
(1) Muth, O.H, J.E. Oldfield, L.F. Remmert, and J.R. Schubert. 1958. Effects of selenium and vitamin E on white muscle disease. Science. 128:1090.
(2) Weiss, W.P. 2002. Selenium nutrition of cattle: An update. Proceedings of the Pacific Northwest Animal Nutrition Conference, pp 1 – 10.
(3) Hemingway, R.G. 2003. The influences of dietary intakes and supplementation with selenium and vitamin E on reproduction diseases and reproductive efficiency in cattle and sheep. Vet. Res. Commun. 27:159-174.
(4) Contri, A. I. De Amicis, A. Molinari, M. Faustini, A. Gramenzi, D. Robbe, Al. Carluccio. 2011. Effect of dietary antioxidant supplementation on fresh semen quality in stallion. Theriogenology. 75:1319-1326.
