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      Wednesday, April 16, 2014

January 09

Animals have specific requirements for minerals. These 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)

 

Calcium (%)

Phosphorus (%)

Magnesium (%)

Barley

.06

.38

.17

Wheat

.07

.38

.18

Oats

.08

.39

.16

Alfalfa Hay

1.54

.22

.40

Grass Hay (Brome)

.57

.16

.18

Barley Silage

.47

.32

.29

Cereal Straw

.28

.07

.17

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

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).

Calcium

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 performance 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.

Phosphorus

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 for 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:Phosphorus Ratios

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.

Magnesium

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.

Potassium

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.

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, 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.  Remove all salt blocks.  After the cows are accustom 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

  1. Mineral intakes should normally be about 60 gm (2 oz.) per head per day.
  2. Salt intakes should normally be about 45 gm to 60 gm (1.5 oz. to 2 oz.) per head per day.
  3. When feeding dry hay or silage, voluntary intakes generally drop.
  4. Cereal greenfeed and cereal silage can contain very high levels of Sodium which reduces salt intakes.
  5. With hard water (total dissolved solids of greater than 2000 mg/l) mineral intakes are usually lower.
  6. 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 this dietary requirement.

Mineral Supplements

Mineral supplements are available in three broad categories:

  1. 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.
  2. Equal Calcium - Phosphorus (e.g. 1:1 Mineral) This mineral is used to supplement a grain-forage ration or a legume-grass pasture.
  3. 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.

Contact the Agriculture Knowledge Centre for further information   1-866-457-2377 

 



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