Mineral Nutrition’s Affect on Herd Health


Published: Recent Advances in Dairy Nutrition Australia.  Rhône-Poulenc Animal Nutrition, Australia.  Dec 1995

The dairy cow, like all animals, needs more than just minerals to maintain herself and optimize production.  To maintain her condition and health and to provide the additional nutrients necessary for milk production she must receive adequate levels of energy, protein, minerals, vitamins and water.  If one of these five nutrient categories is out of balance, the cow’s health and productivity is jeopardized.

The mineral needs of a dairy cow can be divided into two categories; macrominerals and microminerals.  Macrominerals are minerals which are needed in greater quantities, usually a percentage of the total diet.  These minerals are found in animal tissues at the highest levels (Table 1).

 Table 1

Macromineral Function/Comments
Calcium Required for bone formation, milk production and overall body function.  Low levels in grains.  As plants mature, levels decrease.
Phosphorus Required for bone formation, milk production, energy metabolism and overall body function.  As plants mature, levels decrease.
Sodium Needed to maintain the proper water balance within the cow.  Deficient in both forages and grains.
Chlorine Needed to help maintain the animal’s acid-base balance.
Potassium Involved in water balance and acid-base balance of the animal.  Cofactor for enzymes associated with protein synthesis.  Low in mature, weathered forages.  Over fertilization with potassium may cause problems in Udder Oedema and Milk Fever.
Magnesium Role in many enzyme systems within the cow.  Essential for growth of rumen microbes.  Low levels in lush pastures may cause Grass Tetany.
Sulphur Needed by both the cow and rumen microbes.

Secondly, the microminerals or trace minerals, are required by the animal in very small quantities, parts per million (mg/kg).  Although the quantity required is very small they are still essential for the survival of the animal (Table 2).

Table 2

Micromineral Function/Comments
Cobalt Needed by the rumen microbes to synthesize the B Vitamins required by the dairy cow.  B Vitamins are essential for the production of propionic acid.  Increased propionic acid levels results in an increase in milk yield.
Copper Needed for the enzymes that control energy metabolism, body pigmentation and blood formation.  High levels of molybdenum will cause a copper deficiency.
Iodine Found in the thyroid hormones that control energy metabolism.  Requirements increase during periods of stress.
Iron Requirements are low in mature cows.  Essential nutrient for proper functioning of the immune system.
Manganese Involved in both fat and protein synthesis.  Levels vary widely in feed.
Molybdenum High levels may exist in plants grown of high pH soils.  Interacts with copper.  Found in xanthein oxidase enzyme in milk.
Selenium Involved in tissue integrity and the immune system.
Zinc Involved in over 200 functions within the cow.  Associated with the hormones of reproduction and glucose production.  Levels highly variable in feed.

The immune system is paramount to the health of the cow and minerals are extremely important to allow the immune system to function properly.  Zinc is involved in many areas of the immune system such as lymphocyte function and antibody response.  Manganese is also associated with many segments of the immune system.  Like selenium, iron is involved in the process of maintaining cellular integrity within the animal.  Copper is also involved in many areas of the immune system.  It has been shown that a copper or magnesium deficiency will decrease the cow’s ability to resist infection.

Selenium is a component of the enzyme glutathione peroxidase which has antioxidant properties.  This mineral’s main function is to maintain cellular tissue integrity; therefore infectious agents do not have access to the animal’s internal cellular environment.

Adequate mineral levels are required to help prevent various herd health problems common in today’s dairy herds.  Displaced abomasum, or twisted gut, is an abnormal shift of the cow’s fourth stomach, the abomasum.  This results in a decrease in feed intake and ultimately ketosis.  No known cause exists for displaced abomasum however stress, improper lead feeding (such as abrupt ration changes), acidic rations and high concentrate to roughage levels in the total ration may have an effect.  Feed management considerations such as the processing of the fibre to a very fine level or feeding too much grain over a short period of time may increase the incidences of displaced abomasum.  To aid in the prevention of displaced abomasum the stress levels placed on a cow should be minimized.  Ensuring fibre length is adequate and ration changes occur slowly helps prevent displaced abomasum.  Adequate dietary levels of calcium and selenium are also essential.

Grass tetany is a seasonal problem that plagues many farmers.  The condition is brought on by low magnesium levels in pastures.  Magnesium is involved in the nerve function within the cow.

When magnesium levels are low, the cow exhibits signs of excitability, characteristic of grass tetany.  Lush new forages are low in magnesium and high in nitrogen.  This excess nitrogen is converted to ammonia within the rumen.  The ammonia in turn inhibits magnesium absorption by the cow.  Therefore, the cow is consuming forage typically low in magnesium and the magnesium that is present is inhibited from absorption by the excess ammonia.  The result is a very low magnesium intake.  To prevent this condition, magnesium supplementation during the grass tetany season is warranted.  Pasture animals may be supplemented with a mixture of magnesium oxide with molasses or salt in a 1:1 ratio.  Alternatively, a complete mineral mix with a 25% magnesium oxide may be provided to help eliminate grass tetany (McDowell, 1985).  Pasture fertilization needs to be done to meet plant requirements, but not to excess; as excessive nitrogen fertilization will augment grass tetany problems.

Retained Placenta, commonly known as “not clearing”, is mainly due to interference in the detachment of the placenta membrane or due to a lack of or weak uterine contraction.  Adequate levels of Vitamin A and E and the minerals selenium and iodine are needed to help prevent this condition.  The correct calcium to phosphorus ratio (2:1) must also be maintained within the diet.

Udder Oedema is defined as an excess accumulation of fluid within the udder.  The exact cause is unknown however very high salt levels of approximately 200g/day have been shown to increase the incidences of Oedema.  Buffers fed to dry cows also increase the sodium intake of the cow and therefore can increase Oedema.  High potassium levels in excess of 227g/day have also been associated with Udder Oedema (NRC, 1989).  Farmers can help prevent Udder Oedema by supplying only the needed salt level to the cow.  The cow needs 0.10-0.30% sodium which equates to approximately 0.25-0.50% salt of total dry matter intake.  Feeding anionic salts prior to calving has also been shown to help prevent Udder Oedema.  Proper fertilization of pastures so that potassium levels are not in excess is also helpful.

Laminitis, or foot rot, is common at calving and has been linked to nutritional imbalances or poor feed management which results in acidosis.  Mastitis and Metritis, which is an inflammation of the uterus, are also known to be associated with the onset of foot rot.  A balanced ration, fed properly, will go a long way in helping to prevent the foot disorder.  Increasing the zinc of the diet (2.5% zinc methionine) has been shown to decrease infectious laminitis (foot rot) (Brazle, 1995).  Foot rot or infectious laminitis is also prevented when adequate levels of iodine are included in the ration (0.7ppm).

Milk Fever is caused by a calcium drain on the cow due to the increase demand for calcium associated with milk synthesis and the cow’s inability to mobilize calcium quickly enough to meet her needs.

To help prevent Milk Fever, adequate bone levels of calcium and phosphorus must be obtained in late lactation or the dry period.  This builds up the cow’s calcium and phosphorus reserves which are then called upon during the start of lactation.  If adequate mineral reserves have been built up, it is advantageous to limit calcium levels to 20g/day for three weeks prior to parturition.  In doing so, the cow is preparing her system to use her body stores for calcium and therefore the demand placed upon her for calcium at parturition can be met.  Low levels of calcium intake are extremely hard to achieve as most forages have high calcium levels.  Alternatively, anionic salts can be added approximately 21 days prior to parturition (Johnson, 1995).  Anionic salts commonly used are:
      • Magnesium sulphate
      • Ammonium sulphate
      • Ammonium chloride
      • Calcium sulphate

The salts act to create a systemic acidosis that results in a release of bicarbonate from the bones to help neutralize the acid.  With the release of the bicarbonate, calcium and phosphorus are also released from the bones.  When feeding anionic salts it is important that the calcium levels in the total ration are not limited.  The cow will need at least 150g of calcium per day (Johnson, 1995).  Fat cows should be avoided at calving as this condition reduces feed intake and tends to cause an increase in the incidences of Milk Fever.

The level of Mastitis within the herd is always a production and economic concern.  Mastitis is the end result of an interaction of several factors: management, the cow, the environment and various microorganisms present in the environment.  Possible causes of Mastitis are from contagious pathogens such as staphylococcus aureus and streptococci.  We can increase the resistance of the cow to these mastitic pathogens through nutrition.  However, it must be emphasized that no feed can cause or cure Mastitis.  Adequate levels of Vitamin A, D and E are needed, as are the minerals selenium, copper and zinc.

It is important to note that the occurrence of one case of Clinical Mastitis in your herd means 15-40 cases of Subclinical Mastitis occurring.  It is also known that somatic cell counts above 200,000 indicate an increase likelihood of Subclinical Mastitis.

How great is this milk production loss?  In an evaluation of Wisconsin dairy farmers on the Herd Improvement Program, somatic cell counts of 140,000-195,000 resulted in a 5% milk production loss.  A loss of 19-25% in milk production was associated somatic cell counts of 1,280,000-2,280,000 (Philpot and Nickerson, 1991).

The cow will have an increased resistance to these pathogenic organisms when Vitamin E levels in the plasma are greater than 0.4μg/ml and greater than 0.7μg/ml for selenium.  This can usually be achieved when the cow receives 0.3ppm of selenium and 1000mg/day of Vitamin E.  Low plasma levels of Vitamin E and selenium have been shown to increase rates of infection, cause higher somatic cell counts, are associated with infections of longer duration and more severe clinical signs of Mastitis.

The dairy cow needs a balanced nutrition program that includes adequate levels of minerals.  This is essential to help prevent the metabolic conditions associated with nutrition imbalances and at the same time enhance the immune system to help fight pathological agents.