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Minerals for Grazing Cattle

It is a generally accepted fact that mineral supplementation is an important part of ruminant nutrition. Proper mineral and vitamin nutrition contribute to strong immune systems, reproductive performance, and weight gain. A properly balanced mineral program requires consideration of animal nutritional needs, forage/feed intake and its mineral concentration, and mineral supplement intake and its concentration. Diets with mineral imbalances may cause poor animal performance, resulting in reduced profitability.  There are many differences between mineral supplements designed for a grazing/forage system versus a grain-based diet.  Let’s focus on forage system considerations.

At least 17 minerals are required by beef cattle. Macrominerals required include calcium, magnesium, phosphorus, potassium, sodium, chlorine and sulfur. The microminerals required are chromium, cobalt, copper, iodine, iron, manganese, molybdenum, nickel, selenium and zinc. Other minerals, including arsenic, boron, lead, silicon and vanadium, have been shown to be essential for one or more animal species, but there is no evidence that these minerals are of practical importance in beef cattle.

Vitamins of importance include Vitamin A, D and E. Other essential vitamins are usually present in adequate quantities in the diet or are synthesized by bacteria in the rumen.

Mineral requirements are dependent on forage mineral content, animal age, and stage of production. However, simply knowing the animal’s requirement is only one component in evaluating an animal’s mineral status. Mineral needs also tend to be area specific and change with soil type, fertilization rates, rainfall, and other factors.

Forage mineral concentration is extremely variable and site-specific.  Investing a few dollars to test forages, so that you know mineral levels in your hay and pastures enables you to make smarter supplements decisions. The table below shows average mineral concentration in five types of forages common to Georgia and compares these averages with requirements of lactating and growing cattle.

Table 1. Average mineral concentration of common Georgia forages and dietary requirements of beef cattle.

MineralBahia PastureBermuda PastureBermuda HayFescue PastureFescue HayLactating Cow RequirementsGrowing Calving Requirements
Calcium %0.460.390.430.510.510.310.58
Phosphorus %0.220.260.200.270.370.210.26
Potassium %1.451.31.612.32.30.600.70
Sulfur %0.210.280.210.190.180.150.15
Copper ppm8.09.09.05.86.010.010.0
Zinc ppm20.020.020.018.722.030.030.0

a Adapted from NRC, 2000.

A mineral deficiency is difficult to diagnosis and often silently robs profits and efficiency from the herd.  Many of the clinical signs of a problem are not evident until a severe deficiency exists because bone, blood, liver, and other organs provide a substantial pool from which cattle can draw during times of dietary inadequacy. Mineral deficiencies should always be a concern when animals graze pastures that have been under stress (e.g. drought) over a prolonged period of time.

Controlling daily intake of minerals can be challenging. The form the mineral is in and what type of feeder will influence intake.  Regular monitoring of mineral consumption can help combat intake problems. Selecting a mineral brand that is more palatable could help increase consumption, while adding a limiting factor, like salt, could help slow consumption.

Mineral supplementation is not a one-size-fits-all program. Each operation’s decision will be different based on their animals’ requirements, nutritional system, and forage mineral availability. However, understanding that mineral and vitamin nutrition is vital to overall herd health and reproductive efficiency is the first step. For more detailed information refer to UGA Publication: Mineral Supplements for Beef Cattle found at https://secure.caes.uga.edu/extension/publications/files/pdf/B%20895_4.PDF .