Balancing Minerals and Vitamins for Production, Reproduction and Health

Tim Brown

# Take Home Messages

• Laboratory analyses of feedstuffs for mineral content are essential for balancing minerals in the diet.
• When selecting sources of supplemental minerals, only those of high bioavailability should be considered.
• The feeding of minerals in excess of established requirements should be avoided except in certain situations where more of a particular element has proven to provide benefits to the animal.
• Diets for lactating cows should be fortified with around 100,000 IU vitamin A and 10,000 IU of vitamin D per day, particularly when stored forages (hay, silage) are fed.
• Diets of dairy cows should be fortified with around 1,000 IU and 500 IU of vitamin E during the dry period and lactation, respectively.

# Introduction

The objectives of this paper are: (1) To discuss the differences between the concept of Abalancing@ rations for minerals and vitamins and that of Afortifying@ rations with these nutrients, (2) To briefly describe some of the mineral and vitamin requirements of dairy cattle, and to provide reference sources for more detailed information on mineral and vitamin requirements and metabolism. (3) To provide examples of how to determine the adequacy of dietary minerals based on laboratory analyses, and how to calculate the amount of mineral supplement that is required. (4) To provide some practical guidelines for fortifying dairy rations with minerals and vitamins to prevent a few of the more common production, reproduction, and health problems in today=s modern dairies.

The nutritional concept of Abalancing@ minerals and vitamins involves our attempts to provide, in the diet, appropriate amounts of available nutrients to meet the animal=s requirements (maintenance, growth, production, reproduction, and health) while at the same time, preventing interactions among the nutrients that will limit the animal=s ability to use them. When we formulate diets for livestock, we frequently consider that we are Abalancing A all of the minerals and vitamins in the ration. However, for some of these, we often are merely providing supplementation or fortification to ensure that the nutrient supply to the animal falls into a rather broad range, somewhere between levels that are so low that they cause losses of production efficiency, and so high that they cause imbalances, toxicities, or exorbitant costs. Often, our ability to truly balance for certain minerals and vitamins depends on the information that is available to us regarding the content of those nutrients in our feedstuffs, and the absolute availability or activity of those nutrients for metabolism by the animal. We generally have more concrete information to work with when we evaluate feedstuffs for mineral content than we do when we try to gather information on the vitamin content or vitamin activity of feedstuffs. The mineral concentrations in our feedstuffs, particularly forages, are variable from load to load, and are affected by a number of factors, necessitating a laboratory analysis to tell us what those values are. However, minerals within the feeds are quite stable, and once we have analyzed those feeds, the mineral content is unlikely to change appreciably. On the other hand, the vitamin content of our feedstuffs will change over time, so we can never have a great deal of confidence in how much vitamins our cattle are getting from the feeds. Thus, for minerals, we are able to come closer to actually matching dietary supply to metabolic needs, whereas for vitamins, we depend more on Afortification@ of the diet to remain within Atolerable@ levels. Some of the factors that affect our ability to balance minerals and vitamins in dairy rations include:

Numerous excellent discussions of the above-mentioned factors have been published (1, 4, 11, 12, 14, 17). Our concern in today=s dairy nutrition programs is not preventing the development of the classical deficiency symptoms that research has characterized for each mineral and vitamin, but is avoiding losses in production efficiency that result from sub-optimal levels or improper ratios of these nutrients in the diet.

 # The Mineral and Vitamin Requirements

There are so many variables that affect the manner in which dietary minerals and vitamins are used by animals that science has not been able to definitively determine the absolute requirement for each of these nutrients under every condition. For the purpose of providing practical guidelines for mineral requirements, certain assumptions have had to be made. Depending on which research data are evaluated, differing conclusions can be drawn regarding the absolute mineral and vitamin requirements of the animal, and different recommendations can be made regarding the optimum concentrations of these in the diet. One rich source of information regarding dietary mineral requirements is the National Research Council=s (NRC) Nutrient Requirements of Dairy Cattle (14). This publication represents a survey and critical review of the published scientific literature on dairy nutrition. Despite the fact that we are still refining our knowledge of mineral and vitamin nutrition and metabolism, we have come a long way, and the classic mineral and vitamin deficiency symptoms of yesteryear are rarely seen in today=s well managed dairy herds. Some ranges in the NRC recommended mineral content of diets for lactating cows and the recommended maximum tolerable levels for certain minerals and vitamins are listed in Table 1.

Several universities, feed manufacturers, and nutrition consultants will recommend dietary mineral and vitamin levels that differ from those in the NRC. Many of these deviations from NRC have merit based on recent research and field observations. However, dairymen are cautioned against indiscriminate overfeeding of any mineral or vitamin with the attitude that Aif my cow needs just a little of this, more will be better@. Mineral imbalances created by indiscriminate over supplementation can be just as detrimental as simple deficiencies. A few of the more common trace mineral recommendations that differ from those of the NRC requirements are listed in Table 2. Some recommendations for feeding supplemental vitamins in excess of NRC recommendations are given in Table 3. Some of these recommendations likely will change as we learn more about specific involvement of minerals and vitamins in dairy cattle production, reproduction and health.

Evaluating Rations For Mineral Content

Fortunately, for many of the minerals of nutritional interest, reasonably priced laboratory analyses are generally available. The important questions are Afor which minerals should I analyze, how many of my feedstuffs should I analyze for minerals, and how often should I do it?@. The minerals that are most commonly analyzed in feeds are calcium, phosphorous, magnesium, sodium, potassium, copper, zinc, manganese, and iron. Although there are other minerals for which we also need to be concerned (chlorine, sulfur, cobalt, iodine, selenium), these generally are more difficult and expensive to analyze in the laboratory, and thus, we tend to rely more on Abook@ values for these elements. We must remember, however, that the more Aguesses@, or book values, that we use, the less confidence we will have in our final analysis of mineral adequacy in our rations. Generally, the mineral content of forages varies more than that of grains and by-product feeds. As such, if you want to save some analytical costs, just analyze your forages for mineral content. This will reduce your confidence in the mineral content of those grains and by-products, but Abook values@ for these will be closer to correct than will be book values for the mineral content of the forages. An analysis should be obtained for each newly purchased lot of forage, and for each home-grown forage for which the production conditions suggest that there may be differences in nutrient composition (different fields, harvest dates, fertilization rates, weathering conditions, etc.). When one considers the time and effort it takes to sample feeds, and the expense of analyzing the feeds, the concept of the Total Mixed Ration (TMR) greatly simplifies our efforts. With a TMR, where all feeds and supplemental ingredients are incorporated into the ration, we can simply send the complete mixture to the laboratory and compare the results directly with the animal=s dietary requirements. However, those who do not feed a TMR (component feeding) will need a mineral analysis (or book value) for each feed, and make a few calculations (example provided below) from the results. Of course, we have available to us many user-friendly ration balancing and ration evaluation computer programs that provide great utility for assessing nutrient adequacy in cattle diets.

 # Calculating Dietary Mineral Concentration from Analysis

 .165 kg total calcium ) 21.8 kg total DM intake x 100 = .76% calcium in the total diet dry matter. You can then compare this number to the figures in the nutrient recommendation tables for your particular size of cow and her production level. You will see that .76% calcium in the diet falls in the upper range of NRC recommended calcium levels.

218 B 108 = 110 mg supplemental copper needed per day.

Divide the amount of supplemental copper you need by the copper concentration in the supplement (110 mg copper needed ) 8,800 mg copper/kg supplement) = .0125 kg supplement, or 12.5 grams of this supplement per cow per day. Remember to take into account the contributions that this much supplement will make to the zinc and manganese levels in the ration.

 # Bioavailability of Minerals from Different Supplements

Bioavailability is the term used to describe the degree to which minerals from different sources can be used by the animal. Simple solubility of the mineral elements seems to be one of the major factors affecting bioavailability, thus, mineral supplements from which the elements are readily soluble in water will be the most bioavailable. A laboratory analysis of the mineral content of feedstuffs will not provide an estimate of their bioavailability. However, the bioavailability of minerals from feedstuffs has been estimated and those estimates have been taken into account in calculating the recommended mineral levels in dairy diets (14). All dairy rations will require some supplemental minerals. The objective of supplementing the ration is to provide elements that the animal can use. Unfortunately, many sources of supplemental minerals have limited ability to provide Auseable@ minerals to the animal. Dairymen are encouraged to avoid the mineral supplements known to be low in bioavailability. Table 4 lists a few common supplements and their relative bioavailability.

The cost of mineral supplements also needs to be considered when deciding which source to use. The marketing of mineral supplements is highly competitive, and marketing claims abound regarding superiority of one source over another. Perhaps one area in which marketing is most aggressive today is in the promotion of Aorganic@ trace minerals. These come in the form of chelates, proteinates, and complexes in which the mineral element is chemically attached to an organic molecule(s), usually amino acids or pieces of protein. Peer review research has shown that in some instances organic mineral supplements are better at improving immune system function, reducing somatic cell counts, improving reproductive performance or improving hoof health. However, in most of these cases, the difference in performance between the organic source and highly bioavailable inorganic sources has been slight. This research indicates that the organic mineral sources are themselves highly bioavailable, but, from a practical standpoint, one should only pay slightly more per unit of element supplied for the slight advantage over a good inorganic source.

 # Practical Considerations in Balancing and Fortifying

Raising dietary calcium and magnesium levels when unprotected fats are fed. It is commonly recommended that dietary calcium and magnesium levels be increased to 1.0% and .45% in the diet dry matter, respectively, when ruminally unprotected fats (oilseeds, tallow) are fed. This doesn=t mean that the animal=s metabolic requirement for these elements has been increased by the extra fat, it just means that providing these elements at slightly higher levels in the diet is a cheap, easy, and effective way of overcoming some of the negative effects (depressed fiber digestion, reduced microbial protein synthesis, etc.) of feeding unprotected fats and oils.

# Possible Mineral and Vitamin Applications of the Near Future

Additionally, we have known the metabolic roles for the vitamin choline for a long time, but fortification of dairy diets with choline has not proven beneficial due to the fact that choline is extensively degraded in the rumen. However, in experiments where choline was either infused post-ruminally or fed in a form that resisted degradation in the rumen, production of milk and milk components increased (5, 6). Further research evaluating the benefits of feeding ruminally protected choline may bring about recommendations regarding it=s supplementation in dairy diets. There is currently no consensus among the scientific community regarding whether or not these early indications will prove to be practically beneficial in dairy nutrition. If supplementing choline is beneficial for dairy cattle, further research must define the appropriate amounts and forms of supplementation of chromium and choline that will be most acceptable. Again, supplementation of minerals and vitamins in this fashion is not actually a balancing procedure, but a fortification to achieve improved animal production, reproduction, or health.

 # Conclusion

One must keep in mind that even though the micronutrients in the diet constitute only a small proportion of the mass of the total diet, they are essential for normal health and production. Diligence in evaluating feedstuffs for mineral content is essential for managing mineral nutrition. Careful balancing and fortifying of the diet with minerals and vitamins will help promote high production efficiency and avoid health problems related to minerals and vitamins. Minor errors in our attempts to fortify diets or Abalance@ the micronutrients may cause minor problems in our herds. These minor problems are often unnoticeable, but they can still negatively impact our production efficiency. However, we must not mislead ourselves into thinking that major health or production problems are the result of minor deficiencies or imbalances in the micronutrients. Too often, producers and consultants will discuss the possibility that a difference in a few parts per million of a certain trace element, or a few I.U. of some vitamin in the diet has caused an outbreak of illness or the development of severe reproductive inefficiency or a severe reduction in milk production. In many of these cases, other nutritive, herd health, or management factors have precipitated the observed problems, and the producer should focus his attention first on solving the major problems.

 # References

1. Beede, D. K, W. K. Sanchez and C. Wang. 1992. Macrominerals. Page 272 in Large Dairy Herd Management. Van Horn and Wilcox, eds., American Dairy Science Association, Champaign, IL.
2. Burton, J. L., B. A. Mallard and D. N. Mowat. 1993. Effects of supplemental chromium on immune response of periparturient and early lactation dairy cows. J. Anim. Sci. 71:1532.
3. Cervantes, A., T. R. Smith, and J. W. Young. 1996. Effects of nicotinamide on milk composition and production in dairy cows fed supplemental fat. J. Dairy Sci. 78:105
4. Church, D. C., ed., 1988. The Ruminant Animal. Digestive Physiology and Nutrition. Waveland Press, Prospect Heights, IL.
5. Erdman, R. A. 1992. Vitamins. Page 297 in Large Dairy Herd Management. Van Horn and Wilcox, eds., American Dairy Science Association, Champaign, IL.
6. Erdman and Sharma. 1991. Effect of dietary rumen-protected choline in lactating dairy cows. J. Dairy Sci. 74:1641.
7. Erickson, P. S. M. R. Murphy and J. H. Clark. 1992. Supplementation of dairy cow diets with calcium salts of long-chain fatty acids and nicotinic acid in early lactation. J. Dairy Sci. 75:1078.
8. Horner, J. L., C. E. Coppock, G. T Schelling, J. M. Labore, and D. H. Nave. 1986. Influence of niacin and whole cottonseed on intake, milk yield and composition , and systemic responses of dairy cows. J. Dairy Sci. 69:3087.
9. Hutjens, M. F. 1992. Selecting Feed Additives. Page 309 in Large Dairy Herd Management. Van Horn and Wilcox, eds., American Dairy Science Association, Champaign, IL.
10. Jaster, E. H., G. F. Hartnell, and M. F. Hutjens. 1983. Feeding supplemental niacin for milk production in six dairy herds. J. Dairy Sci. 66:1046
11. McDowell, L. R. , J. H. Conrad, G. L. Ellis, and J. K. Loosli. 1983. Minerals for Grazing Ruminants in Tropical Regions. Department of Animal Science, Center for Tropical Agriculture, University of Florida, Gainsville.
12. Miller, J. K., and F. C. Madsen. 1992. Trace Minerals. Page 287 in Large Dairy Herd Management. Van Horn and Wilcox, eds., American Dairy Science Association, Champaign, IL.
13. National Research Council. 1980. Mineral Tolerances of Domestic Animals. Natl. Acad. Sci. Washington, DC.
14. National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6^th rev. ed. Natl. Acad. Sci. Washington, DC.
15. Sharma and Erdman. 1989. Effect of dietary and abomasally infused choline on milk production responses of lactating dairy cows. J. Nutr. 119:248.
16. Spears, J. W., E. B. Kegley and J. D. Ward. 1991. Bioavailability of organic, inorganic trace minerals explored. Feedstuffs 63(45):12.
17. Underwood, E. J. 1977. Trace Elements in Human and Animal Nutrition. 4^th ed. Academic Press, New York.
18. Weiss, W. P., J. S. Hogan, D. A. Todhunter, and K. L. Smith. 1997. Effect of Vitamin E supplementation in diets with a low concentration of selenium on mammary gland health of dairy cows. J. Dairy Sci. 80:1728.