Seasonal variation in vitamin D status of beef cattle reared in the central United States

Authors: Casas, Eduardo; Lippolis, John; Kuehn, Larry; Reinhardt, Timothy

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2015
Publication Date: 7/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61216
Citation: Casas, E., Lippolis, J.D., Kuehn, L.A., Reinhardt, T.A. 2015. Seasonal variation in vitamin D status of beef cattle reared in the central United States. Domestic Animal Endocrinology. 52:71-74. DOI: 10.1016/j.domaniend.2015.03.003.

Interpretive Summary: Vitamin D is the sunshine vitamin and must be supplemented in the absence of adequate sunshine to produce the vitamin D by sun-exposed skin. Summer provides plenty of sunshine for vitamin production by exposed light colored skin. However, the low sunshine of winter decreases the ability of the body to produce its own Vitamin D. This deficiency is important as Vitamin D supports and maintains bone growth and strength. More recently it has been shown that adequate Vitamin D is needed for white blood cells to fight infectious disease at full strength. This research clearly showed that that while summer sun supported adequate vitamin D production in beef cattle, levels were insufficient during winter months. With small dietary Vitamin D levels and low sunlight, finishing beef cattle ended the winter with vitamin D levels below what the scientific literature says is necessary to support bone growth/strength and maximum disease fighting ability. The data suggest the need for additional supplemental Vitamin D in some beef diets.

Technical Abstract: The objective was to measure seasonal sunshine associated variation in concentration 25-hydroxyvitamin D (25OHD) in beef cattle. Vitamin D is a key modulator of calcium homeostasis, as well as innate and adaptive immunity. Concentrations of 25OHD reflects vitamin D production/intake and vitamin D status. The concentration of 25OHD was measured in crossbred animals born from March-May in 2011 and 2012. Vitamin D status post birth for 2012 calves was measured June 2012. These animals had plasma 25OHD concentrations of 26.3 ± 1.5 ng/mL, which is considered marginal vitamin D status for calcium homeostasis and immunologically deficient. The 25OHD concentrations for late summer were 46.6 ± 1.4 and 51.0 ± 1.5 ng/mL for 2011 and 2012 calves respectively. The 25OHD concentrations for early fall were 63.8 ± 1.4 and 55.2 ± 1.5 ng/mL for 2011 and 2012 calves respectively. Both late summer and early fall values indicate vitamin D sufficiency (P< 0.0001 compared to early summer calves. With diminishing exposure to UVB and consuming ~ 800 IU or 1800 IU (2011 and 2012 respectively) of supplemental vitamin D, the calves midwinter 25OHD concentrations fell to 15.2 ± 1.6 and 16.7 ± 1.5 ng/mL for 2011 and 2012 calves after 4-5 months on a finish ration. (P< 0.0001). This is considered vitamin D insufficiency in most species. Results indicate that calves soon after birth and during winter are marginal to insufficient for vitamin D status by 25OHD concentration. Some individual animals would be classified vitamin D deficient. In the absence of sufficient UVB exposure, the dietary vitamin D requirements for beef cattle need to be reconsidered.