The Importance of Trace Mineral Nutrition

by Aaron Kinser, Ph.D., Vigortone Technical Service Nutritionist

The proper balance of protein, energy, vitamins, and all nutritionally-important minerals is needed to make a nutrition program successful. Nutrient balance is the key to any effective nutrition program. As our knowledge of trace minerals grows, we are finding out that trace mineral deficiencies may limit production in better-managed herds to a much greater extent than generally recognized.

Surveys have suggested that copper and zinc may be limiting nutrients in many situations. In a national forage survey(1) of 352 samples, only 2.5% of the samples contained adequate zinc and 36% of the samples contained adequate copper. Similar deficiencies have been observed in forage samples that Vigortone has collected over the last seven years. In these samples, only 8.3% provided adequate zinc and 36.2% were adequate in copper.

In a Montana study(2), the minerals found most likely to be deficient in forages of the Northern Great Plains were phosphorus, sodium, potassium, zinc, and copper. Cattle cannot perform to their genetic potential if their mineral needs are not met, even if they receive 100% of their protein and energy needs.

These surveys suggest that nearly all forages are deficient in one or more minerals and that there is a widespread occurrence of the deficient levels of copper and zinc for beef cattle grazing forages. In addition, trace mineral concentrations in forages vary much more than do protein and energy concentrations. This is further complicated by the fact that the availability of minerals may be affected by the distribution and form of minerals in the feedstuff, as well as interactions with other minerals or dietary components that inhibit absorption or utilization of a given mineral. North Carolina State University researcher Dr. Jerry Spears suggests that mineral deficiencies in ruminants fed forages often result from low availability rather than low concentration of a given mineral(3).

Trace mineral concentrations and availability are affected by four interdependent factors(4):

1) the genus, species, or variety of crop

2) type and mineral concentration of soil

3) stage of plant maturity

4) climatic or seasonal conditions.

Genus, species, or varietal effects: In general, legumes are higher in calcium, copper, zinc, iron, and cobalt than grasses. In contrast, grasses tend to be higher in manganese and molybdenum than legumes when grown on the same soil. Research has shown that even variety within a species affects mineral composition.

Mineral concentrations in soils: Plants react to inadequate supplies of trace minerals in soil either by reducing the concentration of the element in their tissue or by reducing growth, or a combination of both. However, it should also be recognized that optimal trace mineral supplies for plant growth may yield feeds that are deficient. For example, the iodine, selenium, and cobalt concentrations needed for optimal plant growth are much below the requirements of animals. Mineral concentration in soils has a great effect on pH, which in turn has a major impact on mineral uptake by plants. For example, molybdenum uptake increases as soil pH increases which adversely affects copper availability.

Stage of maturity: Forage trace mineral concentrations are more affected by maturity than that of grains. Generally, there is a rapid uptake of mineral during early growth and gradual dilution as the plant matures. Cobalt, copper, iron, molybdenum, and zinc are the most common minerals affected by plant maturity.

Climatic and seasonal conditions: In general, seasonal or climatic conditions that maximize yield often have no effect or decrease trace mineral concentrations. Leaching of soluble nutrients from forages during wet weather is well documented. However, copper, manganese, and zinc tend to be bound in plant tissues and are less susceptible to leaching than minerals like potassium and phosphorus. As forages stand through to fall and winter, typically leaves and seed heads will be lost. These portions of the plant often contain greater concentrations of the trace minerals than the stem. Consequently, the mineral concentration of standing forage usually decreases due to a change in leaf to stem ratio.

Increasing Emphasis On Trace Minerals

Dr. Dennis Herd at Texas A&M University has suggested that trace mineral supplementation needs are greater today than ever before because of the following reasons:

1. More is known about essential functions of trace minerals and production losses resulting from marginal deficiencies, which often existed in the past but were not recognized.

Dr. Cheryl Nockels at Colorado State University addressed the topic of marginal nutrient deficiencies. Nockels suggests that many people think that mineral and vitamin deficiencies only occur when visible signs are present. Possibly this occurs because most of the mineral and vitamin texts used in teaching nutrition courses show illustrations of different animal species exhibiting clinical signs of deficiency. However, very seldom are nutrient deficiencies so severe that clinical symptoms are observed. As a result, Nockels suggests that many producers think as long as their cattle look fat and healthy that no nutrient deficiencies exist.

Dr. Lee McDowell at the University of Florida emphasizes that subacute deficiencies (marginal) can exist, although clinical deficiency signs do not appear. McDowell further proposes that borderline deficiencies are both the most costly and the most difficult with which to cope and often go unnoticed and unrectified, yet they may result in poor and expensive gains, impaired reproduction, or depressed reproduction.

2. Increased genetic potential and productivity of cattle have probably increased requirements.

Not only has genetic potential increased, but today cattle are generally pushed to perform much nearer their genetic potential. Generally, producers do a good job of feeding adequate protein and energy, but frequently less emphasis is put on mineral nutrition, particularly trace minerals. Copper appears to be the trace mineral which is influenced to the greatest degree by genetics. Genetics greatly influence copper requirements and susceptibility to toxicity. Canadian research(5) suggested that Simmentals and possibly Limousins have higher copper requirements than Angus and Herefords.

3. The interactions occurring between minerals that effect their availability are better understood than they were in the past.

Many minerals interfere with the utilization of other minerals at levels well below the "maximum tolerable level." Both minerals in the feed and water come into play. Minerals in water frequently are more available than those in feed and thus impact livestock mineral status. All minerals can be involved in interactions, but the effect other minerals have on the need for copper appears more specific and unique than with many of the other minerals. For example, the levels of molybdenum, sulfur, and iron both in the diet and water can affect the availability of copper.

4. Whenever yields of crops have been increased with nitrogen, phosphorus, and potassium fertilizers without accompanied repletion of trace minerals, the content of many of the trace minerals in feedstuffs has decreased over time. This is especially true for shallow-rooted crops.

5. Liming, fertilization practices, and/or industrial pollution may be altering the composition or proportion of minerals in forages in certain areas.

6. Research in recent years has shown that trace mineral deficiencies have a negative effect on the immune system leading to health problems and failures of commonly accepted disease treatments. 

Specifically, trace minerals such as copper, selenium, manganese, iron, and zinc have all been shown to have an impact on the immune system. Research has related deficiencies of specific trace minerals to the frequency and severity of such problems as mastitis, retained placenta, stillbirths, embryo mortality, general reproductive failure, weak calves, and dummy calves at birth without good nursing reflexes, calf scours, abomasal ulcers in calves, pneumonia, and apparent vaccine failure. Reductions in growth and/or fertility are often the second item to be affected by a specific trace mineral deficiency. Both immune system function and performance can be affected by marginal deficiencies.

Summary

Trace mineral nutrition has always been important, but due to the abovementioned factors, trace mineral supplementation needs are greater today than was previously thought. Recent forage surveys have shown that there is a widespread occurrence of deficient levels of plant copper and zinc.

Furthermore, just because trace minerals can be found in plants does not mean they are available to the animal. Soil mineral level, soil pH, climatic conditions, plant species, and stage of plant maturity all factor into the trace mineral content and bioavailability for forages.

For these reasons, it is important that cattle be on a good, balanced mineral program to optimize performance. The data from the Vigortone Ranch Trials clearly illustrates that the Vigortone mineral program improves cattle performance and health.

References:

(1) Corah, L., D. Dargatz and C. Peters. 1996. Nutrient forage survey results: Trace mineral and related nutrient levels. Kansas State Univ. Cattlemen's Day Report of Progress 756:83.

(2)'Grings, E.E., M.R. Haferkamp, R.K. Heitschmidt, and M.G. Karl. 1996. Mineral dynamics in forages of the Northern Great Plains. J. Range Manage. 49:234.

(3) Spears, J.W. 1991. Advances in mineral nutrition in grazing ruminants. Proc., 2nd Grazing Livestock Nutr. Conf. P. 138.

(4) Berger, L.L. 1995. Factors affecting the trace mineral composition of feedstuffs. Salt and Trace Minerals Vol. 26 No. 2. Published by the Salt Institute.

(5) Smart, M.E. and D.A. Christensen. 1985. The effect of cow's dietary copper intake, sire breed, age on her copper status and that of her fetus in the first ninety days of gestation. Can. J. Comp. Med. 49:156.

For more information, please call us at 1-800-553-1712 or email us at contactus@vigortone.com.  Dr. Kinser can be reached at akinser@vigortone.com.