Mineral nutrition is very important for successful beef production because it impacts animal growth, reproduction, milk production and health. Cattle obtain part of their mineral requirements from forage, water and protein supplements, but the remainder of their requirements must be met through mineral supplements.
The big question is: "Which mineral supplement is needed for my cattle?" Selection of the right mineral is dependent on the geographical region, forage system, cattle production stage and other factors. Jason Banta of Texas A&M AgriLife Extension provided some considerations in mineral supplement selection at the School for Successful Ranching during the 2019 Cattle Raisers Convention in Fort Worth. The majority of this article was taken from Banta's presentation.
Components of a complete mineral supplement include salt (primarily for its sodium content), macro minerals and trace minerals (also called micro minerals). The supplement also may contain vitamins A, E and maybe D. Macro minerals are expressed as a percentage of the diet, whereas trace minerals are measured in parts per million (ppm) or milligrams per kilograms (mg/kg). The macro and trace minerals are listed in Table 1.
All mineral supplements are not the same due to differences among manufacturers. There are variances among formulations as well as mineral sources. Manufacturer reputation is important. Does it stand behind its product with good technical service? Is the formulation based on a solid research program? Some mineral supplements contain palatability enhancers and some don't. A mineral supplement should have rain and wind resistance. It is not desirable for a mineral formulation to turn into a hard block when it is rained on.
In addition, you don't want the particles ground so fine that they are easily blown out of the feeder.
Targeted intake varies among mineral products. Previously, it was generally two or four ounces. Today, most of the formulations have a target intake of four ounces. An average intake of three to four ounces per day is acceptable for beef cattle. If targeted intake for a mineral is not listed on the tag, it is easily determined by the selenium content. Commonly, 25 to 27 mg/kg of selenium indicates a four-ounce intake. If the selenium content is 50 to 54 mg/kg, target intake is approximately two ounces per day.
There are three common mineral supplement formulations available in Texas. One of the formulations is a high calcium (typically 14% to 18%) and lower phosphorus (typically 5% to 8%) product.
A second formulation has similar calcium and phosphorus levels, which are commonly around 12% each or 12% calcium and 10% phosphorus.
The third mineral formulation is suitable for cattle on green winter pasture (small grains and/or ryegrass) because it contains moderate to high concentrations of magnesium to help prevent grass tetany. Ensure that salt is included in the mineral supplement because it is important for absorption of magnesium by cattle.
Generally, 5% magnesium is adequate to prevent grass tetany problems. Make sure cattle are eating targeted amounts of minerals because when magnesium is increased, intake decreases. One manufacturer has been able to raise the magnesium content to 13% and maintain consumption with a palatability enhancer.
Common additives found in mineral supplements include insecticides, antibiotics and ionophores. Insect growth regulators are added primarily for horn fly control. Cattle pass the insect growth regulators through their digestive tract and excrete it in their feces. Horn flies are controlled as they hatch in the manure.
Certain mineral supplements contain chlortetracycline antibiotic and are sometimes used in areas where anaplasmosis is prevalent. These supplements require a Veterinary Feed Directive, which is a written statement that authorizes the owner or caretaker of animals to obtain and use animal feed containing Veterinary Feed Directive drugs such as antibiotics.
The ionophores -- Bovatec and Rumensin -- are used in some mineral supplements. These ionophores are used to increase feed efficiency or body weight gain by altering ruminant fermentation patterns. Make sure to follow label directions if using a mineral supplement with an ionophore. The product may be approved for use in growing cattle, but not for use in cows.
There is a long list of additives offered for sale that are not well-researched and have limited or no benefits. Use caution in accepting claims that are not supported by legitimate research. Also watch for selective research reporting where partial results are reported to make the product look better than it is. Ask for research sources to establish whether the studies were done by qualified and impartial investigators. Obtain the original research reports to determine if they support the claims made by the company selling the product.
Performance of many additives on the market will not justify their cost.
Macro mineral considerations
On native rangeland, mineral concentrations decrease over time in dormant grass, especially phosphorus and potassium. Rangeland grasses include species such as big bluestem, little bluestem, Indiangrass and switch grass. Bermuda, bahia, dallis and old world bluestems, such as KR bluestem, are examples of introduced grasses. A different mineral supplement may be required when cattle graze dormant range grasses than the one fed during the growing season.
A two-to-one ratio of phosphorus to calcium is recommended for beef cattle diets, but this ratio often is altered by protein and energy supplements. The ratio is corrected by adding calcium to the feed supplement when needed. Many people think that high levels of phosphorus will improve reproduction; however, once nutrient requirements are met, extra phosphorus will not have any effect.
Many rangeland soils are high in calcium or they overlay a limestone base. This does not mean, however, that the range grasses take in more calcium. Bermudagrass averages 0.43% calcium whereas native forages average 0.48%.
In coastal regions, mineral intake by cattle often is challenging because of the forage salt content. It is possible to increase intake by feeding a low-salt mineral formulation such as ADM AMPT-T Low Salt or Purina Coastal Cattle Mineral. Molasses-based mineral tubs also can increase mineral consumption.
Milk fever is a disease characterized by reduced levels of calcium in the cow's blood. The disease occurs following calving at the onset of lactation when calcium demand for colostrum and milk production exceeds the cow's ability to mobilize it. Increasing calcium content in the mineral supplement and lowering the phosphorus level can help avoid milk fever.
Trace mineral considerations
Dietary requirement of copper, zinc and manganese in mineral supplements is a ratio of 10-30-40, but most formulated minerals have either 1-4-2 or 1-3-2 ratios. Many products contain considerably more copper than needed. A few products have amounts of copper that are concerning because high levels have been reported to reduce average daily gain. Copper has no effect on female reproductive capability and probably none on bulls. Zinc is important for ovarian remodeling and corpus luteum production which is essential for establishing and maintaining pregnancy. In males, zinc impacts testicular growth. Manganese possibly affects estrous, but there are no reports of the mineral affecting reproduction in the male.
A 1,250-pound cow requires about 1.30 milligrams of selenium per day. The FDA limit for feeding selenium is three milligrams per day, which is about 2.31 times the nutritional requirement for cattle. Toxicity could result from cattle obtaining selenium from multiple sources in amounts that raise their intake well above requirements.
Preferred forms of iodine in mineral supplements are calcium iodate and EDDI, an organic form. Too much calcium iodate in a supplement has been reported to reduce weight gain and feed intake. Don't use potassium or sodium iodate, because they are less stable than calcium iodate and EDDI.
There are two types of vitamins: water soluble and fat soluble. The B vitamin complex is water soluble and vitamins A, D, E and K are fat soluble. Vitamin A deficiency can occur during winter and drought, but when cattle are grazing green grass, they get plenty of vitamin A. Symptoms of Vitamin A deficiency include birth of dead or weak calves, frequent occurrence of retained placentas and impairment of sperm production. To avoid vitamin A deficiencies, make sure it is in the mineral supplement when green grass is not available.
When selecting a mineral supplement, it is wise to consult a qualified animal nutritionist for help in matching the right product to your situation.
Photo by Robert Fears
Dormant native grass - Mineral concentrations decrease over time in dormant native grass.
Photo by Robert Fears
Targeted mineral intake - Targeted mineral intake may be hard to achieve on coastal pastures.
Photo by Robert Fears
5 percent magnesium - Five percent magnesium is adequate to prevent grass tetany on winter pasture.
Photo by Robert Fears
High calcium - High calcium soils do not increase calcium in plants.