The Value of Vitamin A

Barry Whitworth, DVM – Area Food/Animal Quality and Health – Specialist for Eastern Oklahoma

A ranch in Australia experienced an abnormally high number of stillbirths and weak born calves in 2004-2005. An investigation revealed that the usual infectious causes were not the problem. After additional testing, veterinarians diagnosed low levels of vitamin A as the cause.

According to Dr. Greg Hanzlicek, with the Kansas State Veterinary Diagnostic Laboratory (KSVDL), Kansas had an unusually high number of stillbirth cases and weak born calves in the spring of 2019. After many laboratory tests, it was concluded that the problem stimmed from a lack of energy, protein, Vitamin A, or combinations of all of these.

Both of the above examples demonstrate the importance of vitamin A in reproductive efficiency. Research has shown that low vitamin A levels during pregnancy are associated with abortions, stillbirths, and weak born calves. In addition to playing an important role in reproductive efficiency, vitamin A is essential for vision, bone growth, and maintaining epithelial tissue such as skin and hooves.

Animals obtain vitamin A from consuming green forage and/or the addition of vitamin A supplements to the diet. Lush green pastures contain high amounts of vitamin A. As plants mature and during times of drought, the amount of vitamin A decreases. The ranch in Australia experienced below average rainfall in the previous two years prior to the calving season. During the calving season, rainfall was below average with very dry conditions and little green forage was available.

In general, animals obtain adequate amounts of vitamin A by grazing green forage. Animals grazing green pastures will build a healthy store of vitamin A in the liver. When vitamin A is in short supply, the stores in the liver prevent deficiencies. According to Dr. Lalman, Extension Beef Cattle Specialist Oklahoma State University, the stores should last 2 to 4 months during times of deficiency. During times when green forage is not available, vitamin A supplements need to be added to the diet to prevent deficiencies.

When vitamin A levels are deficient, night blindness is one of the earliest clinical signs. Other eye issues include clouding of the cornea, ocular discharges, and possible ulcerations. Skin issues found when levels of vitamin A are deficient include a dry rough coat, scales on the skin, and dry cracked hooves. Other neurological signs include incoordination or gait problems. Seizures may occur due to the increase cerebrospinal fluid pressure. Birth defects have also been attributed to low vitamin A levels.

Animals displaying vitamin A deficiency should be treated immediately with vitamin A injections. If treated early, response is usually rapid and complete. However, delaying treatment may result in irreversible damage. Even with treatment, cattle with vision impairment due to vitamin A deficiency may not regain their sight.

Preventing Vitamin A deficiency depends on producers being attentive to the environmental conditions that favor low vitamin A levels in forage. During these times, producers need to supplement the diet with vitamin A. Producers need to be aware that Vitamin A supplements degrade rapidly, so vitamin A supplements should not be stored for long periods of time. In addition to vitamin A supplementation, research indicates that diets low in protein result in poor absorption of vitamin A. It is important that producers ensure that the rations have sufficient protein levels. Lastly, since colostrum contains high levels of vitamin A, producers need to ensure that newborns obtain adequate amounts of colostrum at birth.

Similar to the Australian example, most of Oklahoma had below average rainfall for the year of 2022. This resulted in pasture quality decreasing earlier than normal. Due to this year’s lack of green forage, liver stores of vitamin A may be inadequate for the animal’s needs. Producers need to ensure that the diets of their cattle have adequate amounts of vitamin A, energy, and protein. For more information about Vitamin A, producers should contact their veterinarian and/or visit with their Oklahoma State University County Ag Educator.

References

Hanzlicek, G. (2019, May). Difficult Calving Season Findings:2019. Diagnostic Insights. www.ksudl.org/resources/news/diagnostic_insights/may2019/difficult-calving-season2019.html.

Hill, B., Holroyd, R., & Sullivan, M. (2009). Clinical and pathological findings associated with congenital hypovitaminosis A in extensively grazed beef cattle. Australian Veterinary Journal, 87(3), 94–98.

Parker, E. M., Gardiner, C. P., Kessell, A. E., & Parker, A. J. (2017). Hypovitaminosis A in extensively grazed beef cattle. Australian veterinary journal, 95(3), 80–84.