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Are Your Grazing Cattle Getting The Trace Minerals They Need?

University of Minnesota Extension, Stearns County News
August 12, 2015

Source:  Emily Wilmes, Extension Educator-Livestock
University of Minnesota Extension
Stearns, Benton & Morrison Counties




Are Your Grazing Cattle Getting The Trace Minerals They Need?
By Emily Wilmes, University of Minnesota Extension

ST. CLOUD, Minn. (08/12/15) — The Upper Midwest is abundant in cool season grasses and grass-legume mixes that are perfect for grazing beef cattle in the summer months.  Pasture should be providing everything your cattle need from a nutritional standpoint.  But, it may not be providing some key trace minerals.  

Calcium and phosphorus are typically high in forages or diets fed to cows in the Upper Midwest. However, magnesium may need to be supplemented when nitrogen or potassium concentration of forages is elevated due to fertilization. Also, many types of forage in the US are limited in two micro-minerals—copper and zinc--and the concentration of selenium (another micro-mineral) is highly variable and can fluctuate from limiting to excessive in various regions of the country.

Minimum trace mineral concentrations (when feeding 2 oz./cow/day) for zinc, copper and selenium in the supplement are 4000 ppm from zinc sulfate or zinc oxide, 800 ppm from copper sulfate, and 10 to 20 ppm selenium in areas where selenium is needed. When formulating mineral supplements for Simmental, Limousin, Charolais, or Maine Anjou cattle and their crosses, it is important to remember that their requirement for copper is 1.5 times higher than the base requirement of 10 ppm. Similarly, Jersey and Brahman cattle are more susceptible to copper toxicity.

Heifers exposed to breeding for their first year are actively growing, and often they may not harvest grass in sufficient amounts, or the quality may be compromised. Nutritional deficiencies experienced during the first breeding year lead to poor winter body reserves and poor reproductive performance during the second breeding. Whether weight gain is required for heifers to winter in adequate body condition or to recuperate from a poor summer forage supply, prudent choice of supplements permits reaching the desired objective in a cost effective manner.

When supplementing energy to grazing cattle, using starch supplements reduces forage intake. However, when supplementing energy in a moderate to high protein supplement, forage intake is not depressed significantly. Therefore, strategies to supplement growing cattle on moderate- to high-quality grassland depend on short- and long-term management goals. If growth is required with no concern for reduction in forage intake, as may be the case for ensuring that lightweight bred heifers undergo catch-up growth, then high-starch formulations are recommended. On the other hand, when attempting to optimize forage use, use of low-starch, high-protein formulations is recommended.



Emily Wilmes
Extension Educator, Ag Production Systems - Livestock
(320) 255-6169
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