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Mineral Supplementation Program Insight

published: January 23rd 2009

Editors Note: Over the next three issues of Southern Livestock Standard, we will take an indepth look at the many factors relating to mineral supplementation and their importance in beef cattle production. Mineral prices have increased dramatically over the last year and this series is designed to help our readers get the most from their mineral program. Information for this series was provided by Johnny Rossi, University of Georgia Extension Service.

Beef cattle require a number of minerals for optimal growth and reproduction. Selecting the correct mineral supplement is important for maintaining healthy animals, and optimal growth and reproduction. Since high-quality forages and/or grains can furnish a large portion of the required minerals, producers should select supplements that will meet animal requirements and avoid excesses that reduce profits and lead to unnecessary mineral excretion. Minerals not provided by feed can be easily and inexpensively supplied with a simple mineral supplement. A good mineral program for brood cows should cost about $10 to $20 per year.
    Minerals essential to cattle nutrition are classified as macrominerals or microminerals, depending on whether they are found at levels greater than or less than 100 parts per million (ppm) in the animal’s body. In this issue we will look at the macromiinerals.
Macrominerals
    The macrominerals required by beef cattle include calcium, magnesium, phosphorus, potassium, sodium, chlorine and sulfur. Macromineral requirements and maximum tolerable levels for beef cattle are shown in Table 1.
Calcium and phosphorus
    Calcium and phosphorus are the major mineral components of the skeleton. Ninety-nine percent of total body calcium and 80 percent of total body phosphorus are stored in the bones. The skeletal stores of calcium and phosphorus are used to meet short-term dietary inadequacies. Long-term deficiencies of either can cause bones to weaken and even break.
    Calcium and phosphorus also play important roles in other bodily functions. A decrease in either or both can cause a decrease in weight gain and/or a decrease in efficiency of gain. During lactation, low amounts of either will reduce milk production. A superior milking cow requires three times more calcium than does a non-lactating cow. A phosphorus deficiency can delay puberty in heifers and can delay mature beef cows from returning to heat following parturition. Cattle also need correct amounts of calcium for the nervous and muscular systems to function properly.
    Proper utilization of calcium and phosphorus is affected not only by the amount of each mineral fed, but also by their ratio. The optimum Ca:P ratio is about 1.5:1, with a range of 1:1 to 4:1 being satisfactory. In some high-concentrate rations, ratios higher than 2:1 have been successful.
    Most grasses are adequate in calcium. Legumes such as alfalfa, peanut, clover and soybean hay are good sources of calcium, but corn silage and sorghum silage are poor sources of calcium. In general, most concentrates are relatively poor calcium sources. One exception is citrus pulp, which is relatively high in calcium concentration (1.9 percent). Corn, corn by-product feeds and sorghum grain are particularly low in calcium content, and cattle fed grain or corn silage-based diets require calcium supplementation.
    Most forages are low in phosphorus, particularly late in the growing season. Cattle are more likely to be phosphorus-deficient during the winter, when they often subsist on dry forages. Concentrates contain moderate to high concentrations of phosphorus. Protein supplements such as cottonseed meal and soybean meal contain moderate concentrations, whereas many by-product feeds such as distillers grains, corn gluten feed and wheat middlings, have high phosphorus concentrations.
Sodium and chlorine
    Sodium and chlorine (salt) provide for the proper function of the nervous and muscular systems. They help regulate body pH and the amount of water retained in the body. A deficiency of these elements causes loss of appetite and inefficient weight gains or body weight loss. Sodium is commonly deficient in diets, but chlorine levels are usually adequate. Both minerals are present in soft tissues and fluids and there is very little storage of these elements, so a constant, daily source of sodium and chlorine must be provided. Cattle will voluntarily consume more salt when forage is young and succulent than when it matures. Silage-fed cattle will consume more salt than those fed hay, and consumption is higher in cattle fed high-roughage diets than in those on high-concentrate diets. As a rule of thumb, cattle consume 0.005 to 0.010 percent of their body weight as salt daily. For example, a mature cow weighing 1200 pounds would consume 0.06 to 0.12 pounds (1200 x 0.00005 = 0.6), or 1.0 to 1.9 ounces of salt daily.
Magnesium
    Magnesium is essential for proper enzyme and nervous system function and for efficient carbohydrate metabolism. A magnesium deficiency is uncommon except for cows grazing lush-growth fescue or small grain pastures during the late winter and early spring, which may cause grass tetany. A high rate of nitrogen and potassium fertilization contributes to grass tetany. Excess potassium inhibits magnesium absorption in both forage and animals. Grass tetany usually occurs following an extended period of cold weather combined with high levels of nitrogen and potassium fertilization. Mature lactating cows are particularly susceptible to grass tetany.
    Grass tetany can usually be prevented by feeding cattle a mineral mixture containing magnesium oxide. A mineral mixture containing 10 to 14 percent magnesium consumed at 4 ounces per day should provide adequate magnesium. Adequate salt intake is also important in the prevention of grass tetany. Avoid using hard blocks to supplement salt when cattle are at risk for grass tetany; supply salt in a loose form to allow for adequate salt consumption. When grass tetany is not a risk, blocks can be used to supplement minerals provided trace minerals are elevated to account for lower intake of block versus loose salt minerals. Animals with grass tetany respond almost immediately to an intravenous infusion of calcium-magnesium gluconate.
Potassium
    Potassium functions in acid-base balance, osmotic pressure and the amount of water retained in the body. Grasses, particularly early lush spring growth, contains adequate amounts of potassium for grazing cattle and supplementation is rarely needed in grazing cattle. However, potassium may occasionally be low in stockpiled forages or hay that was rained upon prior to baling because potassium is soluble and will leach from the forage.