Mineral Requirements for animals
Mineral requirements are based on the type, weight and age, as well as the rate of performance (weight gain, level of milk production, pregnancy, etc.) expected of the animal.
Mineral imbalances and/or deficiencies can result in decreased performance, decreased disease resistance and reproductive failure which results in significant economic losses.
Mineral deficiencies or imbalances occur when the animal's requirements are not met because of low mineral content in the feedstuffs, low biological availability of the mineral, or another mineral or other substances interferes with the absorption of the mineral by the animal.
While animals may recognize their body's need for minerals, the concept of "Nutritional Wisdom" whereby the animal will eat the minerals that it requires and also consume the correct amounts of the required mineral has not been shown to exist. Mineral supplements are not uniformly palatable. Other than dry matter intakes, daily water consumption and satisfying salt intakes, cattle have no known inherent ability to satisfy daily intakes of other nutrients including minerals. This means that cattle may or may not eat mineral supplements offered on a free-choice basis. Water quality, ration composition and variability between individual animals are also factors influencing palatability and intakes.
Therefore, it is necessary to provide the broad spectrum of frequently deficient minerals in the form that the animals will consume, in the quantity that satisfies the requirements.
To ensure adequate intakes of minerals, the best method is to add them to the ration (mix with grain or use fortified pelleted feeds).
Average Mineral Composition of Selected Saskatchewan Feedstuffs
(Source: Prairie Feed Resource Centre 2002 (100% Dry Matter)
|Grass Hay (Brome)
Feed test results will provide producers with an accurate means of matching and supplementing the nutritional levels of their feeds with the specific requirements of the class of animal being fed.
Macro minerals are those that the animal requires in relatively large amounts usually supplied in grams, ounces or a percentage of the diet. They include salt or Sodium Chloride (NaCl), Calcium (Ca), Phosphorous (P), Potassium (K) and Magnesium (Mg).
Forages are usually good sources of calcium, while cereals are at best a marginal source. Legume forages contain high levels of calcium, while grasses contain only moderate amounts.
Calcium is the essential "building block" for the bones and teeth, enzymes, hormones and muscle development. Calcium deficiency is commonly manifested as "Milk Fever" in high producing lactating cows. Abnormal bone growth, reduced milk production, retained placentas, stillborn calves and poor reproductive Alperformance are common symptoms of a calcium deficiency.
Calcium availability and absorption is influenced by a number of factors. Low Vitamin D levels and high levels of dietary phosphorus will reduce calcium absorption. Excess magnesium reduces calcium absorption while a deficiency of magnesium decreases calcium mobilization into the blood which may result in milk fever symptoms in freshening or lactating cows.
Calcium supplementation is easily accomplished by the addition of calcium carbonate (feed grade limestone) to a high grain ration or a 2:1 or 3:1 mineral supplement mix included in the ration or fed free choice. Limestone contains about 36% calcium and is relatively inexpensive. Mineral supplements for cattle are identified by the ratio of calcium to phosphorus. For example, a 1:1 mineral from one company may contain 15% calcium and 15% phosphorus. Another company may sell a 1:1 mineral containing 18% calcium and 18% phosphorus. Most mineral supplements also contain trace minerals and vitamins. Range minerals may also contain salt.
Grains are considered a good source and forages are marginal suppliers of phosphorus. Therefore pasture and forage based diets are generally deficient in phosphorus.
Phosphorus deficiency can result in low conception rates, reduced feed intake, poor feed efficiency, lower growth rate, reduced milk production, reproductive failures and skeletal abnormalities. A common symptom of phosphorus deficiency is often seen as an abnormal habit of eating or chewing foreign substances such as dirt or wood. Since the body pool of phosphorus is low, phosphorus deficiencies of this mineral are very quickly expressed physiologically. A Vitamin D deficiency or an excess in dietary calcium will reduce the absorption of phosphorus. The most critical need or phosphorus is the last trimester of pregnancy (2-3 months pre-calving) and the period immediately prior to breeding season.
Phosphorus supplementation by a free choice high phosphorus mineral supplement for range conditions or inclusion of a phosphorus source in a complete ration are methods of providing this important mineral.
Calcium and phosphorus are present in the body in approximately 2:1 ratios (that is 2 parts calcium to 1 part phosphorus). Calcium and phosphorus are absorbed by the animal in the proportions that are present in the diet. Rations with ratios less than 1.5:1 have been shown to be detrimental to production, while rations in the range of 1.5:1 to 7:1 have proven satisfactory. Levels exceeding 8:1 can result in depressed performance.
Common feedstuffs in Saskatchewan are an adequate source of magnesium. Since high levels of calcium and phosphorus intake may decrease the availability of dietary magnesium, care should be taken to correct any deficiencies resulting from this problem.
Grass Tetany or "Green Grass Staggers" is a magnesium deficiency occurring when animals graze lush green pasture. This disease is expressed by nervous twitching and lack of muscle co-ordination. A concurrent clinical symptom may be a calcium deficiency. High potassium levels and nitrogen fertilization of the pasture may cause increased incidences of this condition. Magnesium oxide supplied in the mineral mix will prevent this deficiency.
Forage grown in Saskatchewan usually contain sufficient potassium to meet animal needs. However, cereal grains can be low in this nutrient.
Physiologically, potassium is of major importance in osmotic balance, acid-base balance, and in maintaining body water balance. Growth retardation, unsteady gait, general overall muscle weakness and eating or chewing of foreign substances have been associated with potassium deficiencies.
There is also some evidence to suggest that stressed animals (recently inducted into the feedlot) benefit from potassium supplementation.
Under certain growing conditions (drought, cool growing temperatures, high levels of soil fertility), cereal crops can accumulate very high levels of potassium. Levels exceeding 4.0% have been identified. Normal levels usually range from 1.6% to 1.8%. Excessive levels of potassium can impair calcium and magnesium absorption. Cases of "downer cows" have been identified in cows receiving a cereal forage or cereal silage diet that is high in potassium. This is especially apparent in older cows and cows with higher levels of milk production. Symptoms often occur 3 to 4 weeks prior to calving but may occur during the lactation period. Supplementing the diet with 2 to 4 ounces of limestone per day usually prevents these symptoms from occurring and will help correct an imbalance.
Sodium and chlorine (salt)
Feeds in Saskatchewan do not contain sufficient sodium and chlorine to satisfy animal requirements. Deficiency symptoms manifest themselves as a poor appetite, reduced performance and general unthriftiness of the animal.
Salt is the only mineral that animals show a particular desire to eat and therefore is a useful carrier for the other essential minerals. Salt can also be used to regulate the intake of minerals and feedstuffs.
Micro minerals are needed in trace amounts and generally are in shorter supply within the base diet. Only small amounts of micro minerals pass through milk to nursing calves, making calves reliant on the stores they have in their liver at birth until they begin to ingest forage and supplements as they grow. Calf liver stores at birth largely depend on liver concentrations in the dam. Trace minerals are usually represented in a feed analysis with a ppm (parts per million) or mg/kg unit denotation. Micro minerals can be stored in the liver so constant intake is not essential.
Iron is an essential mineral needed to prevent anemia. Iron is generally abundant in cattle diets, but has an antagonistic relationship with some trace minerals, particularly copper. Surface water is generally less likely than well water to contain excess iron.
Most areas in Saskatchewan tend to be selenium deficient. Clinical signs of selenium deficiency include retained placentas after calving, weak calves, and white muscle disease. Selenium works in tandem with vitamin E and both are critical for reducing the risk of retained placenta and white muscle disease.
If white muscle disease is found in calves, it often shows up 2 to 3 weeks after calving. Calves will appear to be completely healthy, yet unable to stand on their own. While a diagnosis should come from a veterinarian, a layman's method of determining whether a calf has white muscle disease is to pick the calf up and see if its legs go out straight and stiff, like a carpenter's sawhorse. If caught early, the condition is generally easily treated, though not necessarily cured, with an injection of bovine selenium.
Iodine is not a major concern for toxicity, but can be lacking in the diet if producers supplement with non-iodized salt. Iodine deficiencies can result in goiter, decreased reproduction, and foot rot. Iodine supplementation is recommended on a year-round basis as a precautionary measure. It is inexpensive and mixes easily in salt or a mineral package. Most commercial pre-mixed mineral packages include available sources of iodine.
Cobalt is one of the trace minerals that is often overlooked. However, recent research has indicated that it is needed for proper immunological response. Cobalt is an element used to form vitamin B12, which in turn is needed to form propionic acid, one of the critical volatile fatty acids produced in the rumen and used by the cow for energy. Cobalt deficiency or toxicity is rare and most commercially available or custom mineral packages include trace amounts of cobalt to ensure the minimum requirement is satisfied.
Molybdenum is rarely deficient, but more often is in too great of a supply. Molybdenum is one of the most notorious antagonists to copper, especially in the presence of sulfates. Molybdenum and sulfates together will tie up copper in the rumen so that it cannot be absorbed. Molybdenum can tie up copper even once it has entered the bloodstream, making it necessary to increase the amount of copper in the diet.
Molybdenum occurs naturally in the diet, so producers need to ensure that copper is available in great enough amounts to overcome the molybdenum.
Generally for every ppm of molybdenum, there should be 6 to 8 ppm of copper, depending also on iron and sulfates in the diet. Figure 1 illustrates how much faster a cow's copper stores can be depleted in the presence of molybdenum and sulphur. In this experiment, cattle were supplemented to bring their liver copper to approximately 85 ppm. They were then deprived of copper for 98 days. Some of the cattle were fed excess molybdenum and sulphur, while the rest ate a diet free of the antagonists. After 98 days, the excess molybdenum and sulphur lowered copper stores in the liver by twice that of a diet free of antagonists.
Copper is a critical element needed for many biological functions ranging from metabolism of iron, which prevents the animal becoming anemic, to assisting with immune functions and reproduction. Cattle in the Saskatchewan can often be copper deficient, especially in the presence of antagonists such as molybdenum, sulfates and iron, as previously discussed. Often, cattle are sub clinically deficient in copper, leaving producers unaware of the problem.
Clinical signs of copper deficiency are often accompanied by a "rusty" appearance on black-hided cattle or an obvious lack of shedding of the winter coat. Red-hided cattle that are copper deficient will often shed hair that looks more yellow than red.
It should be noted that hair discoloration or lack of shedding is not a guarantee that cattle are copper deficient, but rather raises suspicion of the possibility. Some "blonding" may occur during the summer months, especially in red cattle, that should not be construed as a sign of copper deficiency. Other signs of copper deficiency include diarrhea and scouring of calves and cows, especially during the late summer and early fall.
Copper is one of the most difficult minerals to maintain at an adequate level because of the low concentration of copper in most diets and the frequent presence of high levels of antagonists. It should be noted that breed can affect copper requirements, as well. Clinical trials have indicated that Simmental and Charolais cattle need more copper than Angus cattle because those breeds metabolize the mineral differently.
Zinc is a vital element for immune response, growth, and reproduction. Clinical signs of zinc deficiency include reduced feed intake, thin/unthrifty cattle, and increased prevalence of skin lesions. Stressed cattle that are zinc deficient typically demonstrate higher levels of sickness, lower response to treatment, and longer recovery times than cattle with adequate levels of zinc in their system. Zinc has an interdependent relationship with copper in that increasing the supplementation of both minerals together will result in a greater increase in zinc levels than will supplementing for zinc alone (figure 2). Note in figure 2 that two forms of the zinc-and-copper combination were supplemented – a chelated (or organic) compound and a sulfate (or inorganic) compound.
The difference between chelated and sulfate minerals will be discussed later in this document. Regardless of the mineral form, increasing supplementation of both copper and zinc resulted in higher levels of zinc than supplementing one mineral alone. While zinc tends to work in tandem with copper, there are cases where extreme levels of zinc can tie up copper. However, this scenario is generally of little concern for cattle in Saskatchewan.
Manganese deficiencies are generally difficult to diagnose without clinical tests. Manganese is critical for proper gonad (testes and ovaries) function and development. Manganese deficiencies generally result in reduced fertility, but because there are no true clinical signs of a deficiency, they usually go unresolved. Most mineral packages contain enough manganese to maintain needed levels.
Vitamins are organic compounds required in minute amounts by the body. Vitamins may be fat soluble or water soluble. Vitamins A, D, E and K fall into the fat soluble category, while Vitamin C, niacin, folic acid, biotin and the rest of the vitamin B complex are water soluble. Vitamins are essential for growth, metabolism, reproduction, and animal health.
The fat soluble vitamins are stored in fatty tissue and in the liver. They must be supplied in the diet and they are present in lush growing forages. Water soluble vitamins are produced by rumen microbes in quantities sufficient enough that they need not be supplied as part the diet.
Vitamin A is important for vision, growth, reproduction, maintenance of mucous membranes in the digestive and reproductive tracts, and is also important for immunity. A deficiency in Vitamin A results in reduced fertility and low conception rates, retained placentas, abortion, still births and weak calves. It can also lead to reduced immune response, night blindness and water belly.
Vitamin D is required for calcium and phosphorus absorption, the mobilization of calcium from bone and is important in immunity. Vitamin D is often referred to as the sunshine vitamin and is found in sun-cured forages. When cattle are exposed to sunlight or fed sun-cured forages they may not need supplementation. However, due to reduced daylight hours and cloud cover, supplementation may be required in the winter months. Vitamin D supplementation is required if feeding silage during the winter. Deficiency symptoms include loss of appetite, digestive disturbances, rickets, swollen and stiff joints, irritability, tetany, convulsions, bones that are weak and easily broken and a decrease in blood calcium. Calves may be born dead, weak or deformed.
Vitamin E is important for muscle function and disease resistance. Recent studies show a benefit of supplementing higher than previously recommended rates of Vitamin E. Increased Vitamin E improves colostrum quality, immune function and reproductive performance. A deficiency in Vitamin E will result in retained placentas, reduced fertility and poor growth rates. Vitamin E is expensive but necessary, especially 6 weeks prior to calving and through to re-breeding. It is also necessary for calves at weaning time and during other stressful periods.
Vitamin A, D and E can be injected at 90 day intervals over the winter feeding period, may be added to and fed as part of your daily mineral mix, or included as an ingredient in a fortified pellet.
Methods of Supplementation
Free choice feeding of minerals is probably the easiest and most wide-spread practice of supplying minerals, however with this method of supplementation, wide variation of intake can exist. Free choice intake is dependent on several factors: palatability of the mineral preparation, water quality and hardness, mineral content of the feeds, types of feeds, and physical location of the mineral and individual animal preferences. Mixing salt with the cattle mineral supplement will generally encourage consumption and tends to prevent excessive intakes. However, where a high salt content exists in the feed or water this practice may not hold true. A common mix is one part loose fortified salt to one part mineral. This mixture is fed in a mineral feeder without access to other sources of salt. After the cows are accustomed to this mix, you could use one part loose fortified salt to two parts mineral to encourage higher intakes of mineral.
Thumb rules for cattle free choice mineral intakes:
- Mineral intakes should normally be about a minimum of 60 gm (2 oz.) per head per day or as indicated on the product label.
- Salt intakes should normally be about 45 gm to 60 gm (1.5 oz. to 2 oz.) per head per day.
- When feeding dry hay or silage, voluntary intakes generally drop.
- Cereal greenfeed and cereal silage can contain very high levels of Sodium which reduces salt intakes.
- With hard water (total dissolved solids of greater than 2000 mg/l) mineral intakes are usually lower.
- Location of salt will affect intakes. Higher intakes will occur if salt is placed in an active alley way or near the water source.
These guidelines demonstrate the variability of free choice mineral intakes under different conditions. The guidelines also emphasize the importance of measuring and adjusting mineral intakes to achieve required supplementation levels. Inclusion of mineral supplement in the ration at a level sufficient to meet the animal's requirements is the preferred method of satisfying dietary requirements.
Mineral supplements are available in three broad categories:
- High Calcium - Low Phosphorus (e.g. 2:1 or 3:1 Mineral) This mineral is utilized in high grain rations. Additional calcium can be supplemented by adding feed grade limestone to the ration.
- Equal Calcium - Phosphorus (e.g. 1:1 Mineral) This mineral is used to supplement a grain-forage ration or a legume-grass pasture.
- Low Calcium - High Phosphorus (e.g. 1:2 Mineral) This mineral is used to supplement a ration that is legume forage based or is used to correct a Calcium:Phosphorus imbalance in the ration.
Organic (Chelated) vs. Inorganic Minerals
Organic minerals are called by several different names, including complexed minerals and, more commonly, chelated minerals. Chelated minerals are affixed to an amino acid, usually either lysine or methionine. Inorganic minerals are affixed to a sulfate, chloride or oxide compound. The inorganic compound is the standard industry form of most minerals. Inorganic minerals are more widely used mainly because they are less expensive and in most cases provide adequate nutrition to cattle.
Many assertions have been made that chelated minerals are more advantageous to cattle, but research supporting these assertions is inconsistent when making broad comparisons. When more specific circumstances are considered, the majority of research indicates that chelates have greater bio-availability, especially when antagonists such as molybdenum, sulfates, and iron are present or when animals are under stress. The most common minerals to feed in a chelated form are copper, zinc, manganese, and cobalt. Table 2 illustrates a compilation of research comparing the bio-availability of the most common types of mineral packages available to producers. For the purpose of comparing this data, the sulfate form of copper, zinc, and manganese was considered to be the benchmark for bio-availability. The table is not meant to imply that the sulfate form of the mineral is 100 percent available to the animal, but rather uses 100 percent merely to set the comparison benchmark. As the comparison shows, the chelated forms of minerals are generally more bio-available.
Table 2. Comparison of bio-availability of mineral packages. Data are based on a compilation of research on mineral bio-availability. The availability of the sulfate form is set at 100 percent to serve as the benchmark for comparison purposes. Adapted from Greene 2000.
Common reasons to use chelated minerals
In some cases, using chelates can offer some benefits. Here are some examples for the most commonly used chelates.
Copper, zinc and manganese:
- Chelated copper, zinc and manganese can boost short-term growth and immune response when cattle are under stress from weaning and feedlot receiving, disease challenges, hauling, artificial insemination (AI), nutritional stress (lack of feed or poor feed) and so on. Chelated minerals may also be used to "prime" the immune system prior to these known times of stress as a preventive measure to help cattle cope with the stress. Long-term studies comparing the two forms of minerals show similar results, but the chelated minerals have shown more rapid short-term recoveries from mineral deficiencies. If a deficiency exists, producers may benefit from supplementing with chelated minerals for a specified period of time, then re-evaluating the mineral program once recovery is complete (Spears 1989 and Chirase et al. 1994).
- Producers may also find that chelated minerals are beneficial when dietary antagonists such as molybdenum, iron, and sulfates are present, because chelated minerals are more likely to pass through the rumen and get absorbed from the small intestine rather than getting bound up in the rumen and rendered unavailable.
- Research has shown that chelated minerals can help achieve greater pregnancy rates to AI breeding, especially among cattle that may have endured some nutritional stress before the breeding season (Stanton et al. 2000, Ahola et al. 2004, and Whitehurst et al. 2014).
- Research has also shown that chelated minerals increase liver stores more rapidly. Producers should consider chelated minerals if they know that their cattle will face a mineral shortage in the future or if minerals have not been provided for an extended period (Spears 1989, Eckert et al. 1999, and Rabiansky et al. 1999).
- Chelated cobalt, when compared to other forms of cobalt, has been shown to boost immune response when cattle are exposed to a disease challenge or vaccinations (Sager 2013).
- Commercially available chelated cobalt has been shown to help maintain body condition. As discussed previously, cobalt is required to synthesize vitamin B12, as well as propionic acid. Of the volatile fatty acids produced in the rumen and used by the cow for energy, propionic acid results in the greatest energy content. As with any mineral, assess your particular situation before you commit to a mineral package.
Mineral packages with chelates cost more per ton than typical inorganic mineral packages. For this reason, each producer must analyze the benefits and cost for his or her particular situation. Some may be able to meet their herd's mineral needs simply by feeding a larger amount of the less expensive inorganic minerals.
On the other hand, it may be financially beneficial to feed a chelated mineral at a lower level. The cost/benefit outlook for mineral supplementation changes throughout the year. Many cost-minded producers incorporate chelated minerals at certain times in their production cycle while relying on the inorganic forms at other times.
Life stage considerations
The vast majority of research in chelated minerals (copper, zinc, manganese) has focused on two areas: growth and feedlot performance and reproduction.
Cattle in feedlots generally have not reached full maturity and are still expending energy on growth. Experiments evaluating reproduction have been performed with cattle over a wide range of ages. The cattle that seem to benefit the most from chelated minerals have been less than 4 years of age (those still growing). Replacement heifers have demonstrated improved pregnancy rates to AI when supplemented with chelated copper, zinc and manganese. Responses in the form of improved body condition have been shown across multiple age classes in the research conducted with chelated cobalt (Arthington and Swenson 2004, Stanton et al. 2000, Ahola et al. 2004, Whitehurst et al. 2014, and Anderson et al. 2008).
Injectable trace minerals
Injectable minerals, like chelated mineral supplements, have been shown to be highly available to cattle and have resulted in benefits similar to chelated minerals in regard to immune response, response to vaccines, etc. Given the high bio-availability of injectable minerals, they can be a great addition/supplement to a producer's mineral program. They do, however, provide only a short-term response and should not be the sole source of mineral supplementation provided to a herd. It is neither feasible nor practical to think that producers can "inject" their way to a balanced mineral program. When administering injectable minerals, producers should carefully follow labels and Verified Beef Production guidelines to reduce the incidence of injection site lesions and damage to the end product (beef).
Supplementation Frequency, Final Advice
There is no foolproof method for supplementing minerals, but producers should always follow label recommendations. Feedlots have the opportunity to mix the mineral package with the feed and distributing it daily as part of the ration. Cattle operations in a range setting do not have that luxury and may not be able to distribute mineral supplements more than once every week or two. Fortunately, with the exception of magnesium, cattle can store most minerals in their liver for several weeks. For this reason, it is possible to place a week's ration of mineral supplement out on the range with little fear of something going awry if the cattle go without a supplement for a day or two. If you know your cattle will go without mineral supplements for a time, you may need to feed them higher levels of minerals (and perhaps incorporate chelates) to build up their liver stores in preparation for the upcoming nutritional stress. Take the time to work with a nutritionist to determine the best practice for your operation.
Lastly, consider these final recommendations before buying and using any supplement:
- Take measures to assess your herd's mineral status (e.g., diet nutrient analysis, pregnancy rate, calving distribution, calf health, and blood and liver tissue analysis).
- Test your feeds to determine the mineral content and relate this to the expected intake and the animals' requirements.
- Work with your local Regional Livestock Specialist, nutritionist, or feed industry representative to develop a mineral program that is right for your herd and your management plan. No two operations are the same. What works for you may not work for your neighbour.
- Always follow the label guidelines for mineral supplements and monitor consumption.
- Don't risk the financial consequences of an inadequate mineral program.