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      Wednesday, April 23, 2014

September 2008

Trace minerals are essential to maintain animal health, production and reproduction, but are required in trace or minute amounts.  When not present in sufficient quantity, these trace minerals can cause severe biological problems for the animal and economic losses for the producer.

However, with trace minerals being required in such small amounts, excess supplementation can cause toxicity.  The addition of trace minerals to a livestock ration should be done in consultation with a professional recommendation.

The trace minerals that are of particular concern in Saskatchewan are copper, zinc, manganese, iodine, cobalt and selenium.

Average Trace Mineral Composition of Selected Saskatchewan Feedstuffs
Source: Saskatchewan Feed Test Laboratory (1989)

Feedstuff Copper* Zinc Manganese Iron Selenium
all values  mg/kg or ppm          
Barley 4.28 30.2 18.1 66 .26
Wheat 4.13 28.9 19.9 81 .29
Oats 3.56 27.6 18.4 78 .26
Alfalfa 8.8 23.79 44.5 181.4 .31
Grass Hay (brome) 8.34 19.96 52.51 177.21 .11
Barley Silage 5.44 29.47 30.5 223.3 .21
 
Minimum and Maximum
Requirements of Cattle
Copper Zinc Manganese Iron Selenium
  10 - 100 30 - 500 calves
20 - 1,000
cows
40 - 1,000
50 - 1,000 .1 - 2

* recommended cattle copper levels are toxic to sheep

Copper

Copper deficiency in livestock can result from low dietary copper levels, high levels of the mineral molybdenum, high levels of iron and/or high levels of sulphates in drinking water or in the feed.  The majority of forages grown in Saskatchewan are deficient in copper.

Deficiency symptoms include anemia, loss of colour in the haircoat, digestive upset and poor animal performance (growth, lactation and/or reproduction).  Young animals and high performance animals are particularly susceptible to copper deficiency.  Young calves may express copper deficiency as lameness and/or display bone swellings above the joints.  Other symptoms may include an apparent loss or reduction in immunity to parasites, (i.e. lice and coccidiosis).  Specific areas of the province are more prone to low copper and high molybdenum content of the feedstuffs.

In these areas and where high sulphate (500 mg/l or more) and/or iron exists in the drinking water, additional copper supplement is required in the ration.  High molybdenum levels in forage require additional levels of copper in the ration.  A copper:molybdenum ratio of 6:1 or greater is ideal.  Ratios from 2:1 to 3:1 are borderline and toxic if less than 2:1.  High levels of molybdenum cause binding of copper in the digestive tract, and thereby reduce copper availability to the animal.

Primary copper deficiency (low copper in diet as determined by a feed test) and secondary copper deficiency (failure of copper to be absorbed or utilized) must be treated differently.  Blood plasma copper levels alone are not totally reliable in diagnosis of copper deficiency.  Copper levels in hair samples are highly variable, while liver copper profiles provide a better indicator of the copper status of the animal.

Zinc

Zinc deficiency in livestock is manifested by reduced growth rate, reduced fertility, para keratosis (thickening and scaling of skin cells), loss of hair, dermatitis (inflammation of the skin), and an increased susceptibility to foot rot and other foot infections.  While clinical cases of zinc deficiency are rare, sub-clinical deficiencies can be more accurately assessed with a feed analysis that will help determine a potential deficiency and possible solution.

Manganese

Manganese deficiency in livestock impairs reproductive performance (delayed cycling, silent heats and reduced conception rates), skeletal deformities and contracted (shortened) tendons in new born calves, enlarged joints and reduced birth weight.  There is some evidence that excessively high calcium in the ration predisposes a manganese deficiency.  A manganese/choline interaction has been identified in the "fat cow syndrome."

Since manganese deficiencies can cause reproductive losses, it is recommended that supplemental manganese be available at recommended levels to the animal.  A feed analysis will determine the levels of manganese in the diet.

Iodine and cobalt

Feed source levels of iodine and cobalt are generally very low in Saskatchewan and therefore require supplementation.

Iodine deficiencies can be manifested by weak or stillborn calves, calves that may be hairless, goitre, impaired fertility, retained placenta and increased susceptibility of soft tissue to infection.

Animals have no known requirement for cobalt other than as a constituent of Vitamin B12. Therefore, deficiency symptoms described for Vitamin B12 apply to cobalt.  Deficiency symptoms are commonly expressed by a "starvation-like" body condition, rough hair coat, discharge from the eyes, anemia and reproductive failure.

In the past, supplemental cobalt and iodine were usually provided as cobalt-iodized (blue) salt.  The general availability of Trace Mineralized Fortified Salt provides both cobalt and iodine in addition to copper, zinc and manganese.  The addition of selenium is optional.

Selenium

Selenium deficiency problems are common, especially in the thin black, black and grey wooded soil zones of the province.  Selenium deficiency is most commonly expressed as white muscle disease, but also results in reduced disease resistance, retained placenta and weak or dead calves.  Deficiency symptoms are commonly expressed in calves that tend to "lie around", may lack an aggressive suckling ability, and/or are chronically stiff.

Vitamin E metabolism is similar to selenium and deficiencies can be expressed as having the same symptoms as selenium deficiency.  Vitamin E and selenium are usually administered jointly where clinical symptoms occur.  To some extent, one can replace the other, but not completely.

Since selenium is extremely toxic, great care should be exercised when including selenium in a mineral mix or a ration. Feeding directions for this trace mineral must be followed carefully.

Diagnosis of trace mineral deficiency

Diagnosis of trace mineral deficiencies should be based on a complete assessment of the animal group, a feed and water analysis and sampling, and evaluating of blood and animal tissues (liver biopsy).  Single criteria or individual animal diagnosis is generally not sufficient to adequately address trace mineral deficiency problems.

Due to complex interaction between trace minerals and macro-minerals, as well as the other elements which affect the absorption, retention and utilization, a broad comprehensive overview of the management scenario must be undertaken when developing minimum and maximum levels for a mineral program.

Supplementation

Trace minerals are supplemented as trace mineral supplements or included in trace mineralized salts.  Sufficient concentration of the minerals must be available in the diet and/or supplement to be biologically beneficial to the animal.

Mineral supplements are formulated to provide adequate intakes of minerals when fed at the rate recommended by the mineral manufacturer.  The feed rate varies depending on the supplement formulation, but is generally in the range of 45 - 70 gm (1.5 - 2.5 oz.) per head/day.  Under Saskatchewan conditions, many trace mineral supplements are formulated within the following levels to provide an overall adequate intake of trace minerals.

 

Copper

2,500-4,000

mg/kg

of mineral or fortified salt

Zinc

8,000-12,000

mg/kg

of mineral or fortified salt

Manganese

7,500-10,000

mg/kg

of mineral or fortified salt

Cobalt

40-60

mg/kg

of mineral or fortified salt

Iodine

100-200

mg/kg

of mineral or fortified salt

Selenium

25-120

mg/kg

of mineral or fortified salt

 

While excessive intakes of trace minerals should always be avoided because of the relatively high toxicity effects, the more common problem is that of inadequate and consistent intakes of minerals.

Methods of supplementation

Free choice feeding of minerals is probably the easiest and most widespread 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, this practice may not hold true where high sodium content exists in the feed or water.

Guides for cattle free choice mineral intakes

  1. Mineral intakes should normally be about 60 gm (two oz.) per head/day.
  2. Salt intakes should normally be about 45 gm to 60 gm (1.5 oz. to two oz.) per head/day.
  3. When feeding dry hay or silage, voluntary intakes of minerals generally drop.
  4. Cereal greenfeed and cereal silage can contain very high levels of sodium which reduces salt intakes.
  5. Canola hay or silage contains high levels of sulfur which interferes with copper absorption.
  6. With hard water (total dissolved solids of greater than 2,000 mg/l), mineral intakes are usually lower.
  7. Salt intakes are usually greater if salt is placed in areas where cattle frequent.

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.

Chelates

Chelated mineral supplements are readily available in the marketplace.  Chelates are metal elements bound to organic or inorganic compounds.  Some studies have reported the biological availability of the organic chelates to be higher than the elemental or inorganic chelate form of the mineral.

Producers should carefully analyze the benefits of feeding chelated minerals in relation to the cost of providing them.

Chelated minerals may be useful in a trace mineral program where there are availability difficulties of mineral due to interference of absorption e.g. (sulphate or molybdenum).  Chelates may also be beneficial during critical times of stress, reproduction, or when other mineral supplementation programs have not been successful.

For more information, contact:
Agriculture Knowledge Centre
Toll Free: 1-866-457-2377
E-mail: aginfo@gov.sk.ca  



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