Importance of Minerals for Cattle Health and Fertility.

 By Heather Smith Thomas.

 Minerals are essential nutrients.  For example, sodium, chlorine and potassium are crucial to maintain fluid balances in the body and blood.  Sodium chloride (salt) should always be provided because cattle need more salt than occurs naturally in forages.  Iron is an important component of red blood cells—enabling them to carry oxygen.  Bone formation and milk production depend on calcium and phosphorus.

“Calcium and phosphorus are called macro-minerals because they are required in fairly large amounts.  Deficiency is generally not a problem because these minerals are often present in high levels in many feeds.  Phosphorus supplementation is sometimes needed, however, if cows are on dry grass or crop residues for long periods.  Phosphorus levels in most harvested forages are generally adequate, unless it’s poor quality hay.  Calcium is adequate in most forages, but is higher in alfalfa than in grass.

Other minerals such as copper, iron, iodine, manganese, selenium and zinc are needed in very tiny amounts and are called trace minerals, and they also very important to health.  Adequate levels of copper, zinc, manganese and selenium, for example, are crucial for a healthy immune system and optimum reproduction.  

Reproductive performance in cattle, skeletal development in young animals, health and strong immunity all depend on these important trace minerals.  Some soils and plants, however, are short on various minerals, leaving feeds deficient.   Since the 1950’s, cattle producers have been aware of problems caused by selenium deficiencies (white muscle disease in young calves, retained placenta and infertility in cows, abortions, premature or weak newborn calves).   In most geographic areas of the U.S., soils are deficient in selenium.

Later, researchers found that copper deficiencies were also widespread, resulting in poor hair pigmentation, fragile bones, impaired reproductive performance, poor growth rates and reduced immunity.  Copper supplementation in cattle has improved conception rates and immune responses to vaccinations.

More recent forage and cattle studies have indicated that zinc may be the most widely deficient trace mineral.  Zinc is important in many body systems including production of certain enzymes (particularly for synthesis of DNA and proteins), carbohydrate metabolism, hoof structure and soundness, and male fertility (deficient animals have smaller testicles and reduced semen quality).  Zinc-deficient calves may have swollen feet, scaly skin with open lesions, wounds that take longer to heal, loss of hair, excessive salivation, reduced appetite, reduced feed efficiency and growth rates, and impaired immune systems.  Moderate deficiencies are not so readily recognized, but take an economic toll through decreased growth rate and impaired immunity and fertility.  Calves born to zinc-deficient dams have lower levels of immunity even when fed adequate amounts of zinc.

Manganese, another important trace mineral, is important for proper bone and cartilage formation—which directly affects bone growth in young animals.  It is also crucial for optimum fertility in cows.   Signs of deficiency in calves include skeletal deformities, swollen joints and stiffness.

USDA studies of blood levels for trace minerals in cattle around the country found numerous animals deficient in these 4 important minerals.  In one sampling, 7.8% of animals tested were classified as severely deficient for selenium and another 10.4% were marginally deficient.  

There were some regional differences, with 3.6% of cattle in the central US being severely deficient, compared with 18.6% in the southeast, for instance.  Nearly half of all cattle operations surveyed used supplemental selenium.  Of these operations, 98% used a mineral supplement containing additional selenium.  About 4% gave supplemental selenium via injection, and 4% added selenium to the cattle rations (some operations used more than one method of supplementation).  The percentages of severely deficient cattle were lower in operations that provided supplemental selenium, but there were still some animals that were considered severely deficient.

In 1997 USDA’s NAHMS collected blood-serum samples from 3,902 animals on 411 operations in 23 states to analyze for zinc content, taking into consideration the fact that these levels can fluctuate greatly due to stress or recent dietary supplementation.  This study found that 25.6% of cattle operations tested had at least one severely zinc deficient animal, and 93.9% had at least one moderately or severely zinc deficient animal, and 77 percent of the forage samples collected were found to have inadequate zinc to meet the requirements.  

Many producers today use supplemental minerals to augment cattle diets.  These are often supplied in salt/mineral mixes, provided free choice.  Consumption is varied however, with some animals consuming too much while others eat inadequate amounts or none at all.  Also, other aspects of diet (including certain minerals that may negatively interact with the supplement during digestion) may hinder absorption by the body.  Because of this variability, some operations individually dose their animals by drench, bolus or injection—to make sure the cattle directly receive the necessary minerals.  In recent years, the value of injected trace minerals has been recognized as a reliable way to ensure that cattle receive them.

Selenium Deficiency
Soils and feeds in many regions are low in selenium, and a few areas have too much.  Cattle are unhealthy if they don’t have enough, and unhealthy if they get too much.  Selenium is vital for proper body function, reproduction and a healthy immune system, but in excess it is toxic—causing loss of tail hair or hooves.  

Selenium, along with vitamin E, is crucial for producing an enzyme that protects muscle cells from damage, and is important for muscle function.  According to Dr. Steve Blezinger, a cattle nutritionist in Texas, selenium deficiency has been linked to reduced immunity (reducing the number and activity of cells required for normal immune response), decreased reproductive performance, retained placenta, and general poor performance.  

Selenium deficiency can lead to a wide variety of muscle diseases and weakness, reproductive problems, decrease in fertility, increased susceptibility to disease, and impaired heart function in young animals—especially if dams have inadequate selenium during pregnancy.  Calves may be stillborn or die within a few days of birth.  In some regions, white muscle disease can occur unless the dam was supplemented or the calf is given an injection of selenium at birth.  Calves with white muscle disease may be weak, or die suddenly because the heart muscle is impaired.

Copper Deficiency
Low copper levels in cattle can result in many problems—from poor hair coat to reduced weight gains, impaired immune system, broken bones, or lower reproduction rates.  Often it’s a subtle problem you don’t suspect unless you check copper levels in your animals.  When deficiency is corrected, they do better.

One of the most visible signs of copper deficiency is change in hair color. Black animals develop a red tint and red animals become bleached and light colored.  The coat becomes dull and animals may be slow to shed in the spring.  In young animals, copper deficiency can result in diarrhea and higher incidence of diseases, lameness and poor response to vaccination.  Affected animals may have a stiff gait; the ends of the cannon bones may be enlarged and painful, with sore fetlock joints.  Pasterns may be upright, with the calf walking on its toes.  Bones may be weak and brittle. Heifers may be late reaching puberty and fertility may be impaired.  Cows may be slow to cycle after calving.  

Cattle may develop severe copper deficiency due to excess of other trace minerals such as molybdenum or sulfur.  Deficiency may be primary when there’s not enough copper in the soil or plants grown on those soils, or secondary when other factors prevent utilization of copper.  Elements that bind with copper to prevent absorption by the body include molybdenum, iron, zinc, sulfur, lead and calcium carbonate.  When evaluating a forage sample for copper, always look at the copper to molybdenum ratio.  If forages contain less than 8 to 10 parts per million of copper, they are borderline deficient.  The problem is compounded when molybdenum levels are in excess of 1 to 3 parts per million or when the copper to molybdenum ratio falls below 3 to 1.

Copper levels in forages can vary from year to year, depending on weather conditions, soil factors, fertilization of fields and pastures, etc.  Another thing that makes it difficult to recognize a copper problem is that you often don’t see obvious signs (like discolored hair).  Cattle may have subtle symptoms such as higher incidence of disease, more respiratory problems, or calves with diarrhea or disappointing weight gains.

Forage samples, blood tests or liver biopsies can determine if there’s a problem.  Several strategies can be used to correct a deficiency.  You can supplement with extra copper in a loose salt/mineral mix, or individually dose each animal with oral drenching, copper boluses or injections.  Some of the early copper injection products caused injection site swellings, but newer products such as Multimin (providing copper, selenium, zinc and manganese) are less irritating.  
 
Zinc
According to Dr. Blezinger, zinc is deposited in high concentrations in the liver of the fetus, if the dam has adequate levels in her body, but liver levels decline between 30 days and 9 months of age.  Signs of severe zinc deficiency include swollen feet with open lesions, excessive salivation, loss of hair, reduced appetite and feed intake, reduced feed efficiency and growth, and impaired immune response.

Even if calves have adequate levels of copper, zinc and selenium, stress may still cause problems.  Even if these calves don’t get sick, they may not gain as well as they should.  They may also be at risk for “silent pneumonia” which will lower weight gains. It can be a challenge to get calves to eat enough mineral supplement.  Blezinger suggests incorporating an injectable produce into management programs.  “Periodically injecting the cows (with an injection 30 to 60 days prior to calving, and again 30 days prior to rebreeding) and the calves (at birth, and again just prior to weaning) will significantly improve trace mineral status and performance,” he says.

“The developing fetus is totally dependent upon availability of essential nutrients from the dam’s blood.  From conception through birth, and up to weaning age, the cow is either the sole source of nutrition the calf receives, or a significant part,” says Blezinger.

Probiotics And Prebiotics
In recent years, the use of probiotics and prebiotics in animal feeds has been shown to benefit digestion, animal performance and the immune system.  It is essential that the microbial population of the rumen be healthy and in appropriate numbers and balance for proper digestion of feed, and health of the animal. Probiotics are products that contain living microorganisms—bacteria and/or yeasts.  

Probiotics do not directly ferment fibrous material, but help maintain a healthy gut balance.  Yeast cultures indirectly improve fiber digestion.  Probiotics include bacteria and yeast cultures, whereas prebiotics are non-digestible sugars that play a beneficial role in aiding the “good” microbes and protecting against the “bad” ones.

Kyle Newman, PhD, microbiologist and lab director at Venture Laboratories in Kentucky says probiotics seem to prime the digestive system so there isn’t much chance of problems with acidosis; the rumen can handle it better.  “In addition, the lactic acid produced by the probiotic bacteria is normally in a form more utilizable by the host animal.  This is the principle behind a lot of the probiotics,” he says.

“When the lactic acid is there and in a tolerable form, it can be gluconeogenic.  There are certain rumen bacteria that can convert lactic acid into propionic acid, which can be used by the host animal for energy.  That’s another benefit for using probiotics, in terms of energy metabolism,” says Newman.

“The most widely studied use of probiotics is that these ‘good bacteria’ are playing musical chairs with bad bacteria and trying to crowd them out so they cannot cause disease in the host.  There is a lactobacillus product that Dr. Mindy Brashears developed at Texas Tech.  She produced a probiotic and showed that feeding it reduced the numbers of E. coli O157:H7 in the gut.  This E. coli is not a problem for cattle, but is a bad thing when it gets into human food.  This discovery was interesting, in providing an aid to help eliminate this dangerous pathogen,” he says.

Prebiotics are a bit different.  He explains that prebiotics are non-digestible or barely digestible by the mammalian enzymes in the gastro-intestinal tract.  “Prebiotics may help feed the beneficial microbes that are already in the gut or may provide inert material that has some beneficial effect on the animal,” he says.

“Sometimes you mix probiotics and prebiotics together to produce an additive beneficial situation.  In other instances you may use the prebiotic by itself, but the good bacteria must already be there.  The strict definition of a prebiotic is that it’s something that can be utilized by beneficial bacteria in the gut,” says Newman.

“However, one of the most prominent prebiotics on the market are the mannan oligosaccharides (MOS).  They do many things in the body, and are amazing, but they don’t feed the good guys.  They have mannose sugar in a complex form that prevents bad bacteria from using it as an energy source, but a lot of bad bacteria like mannos and are attracted to it.  Thus the prebiotic provides a binding site that the bad ones stick to, like flies on fly-paper, and take them on through the tract and prevent them from colonizing the animal and causing disease.  The bad bacteria stuck to the MOS ultimately die, and pass through the animal,” says Newman.

Alltech has a product called BIOMOS, which is probably the dominant prebiotic on the market.  Newman has done a number of studies on this product and found that it helped the immune system.  “It decreased respiratory infections in newborn calves dramatically.  There are studies that show it can enhance immunoglobulins in cattle as well as in the offspring that get the colostrum from those cattle.  Studies have documented the effect it has on the beneficial bacteria and in reducing pathogenic bacteria,” he says.

“It has also been shown to help repair and improve the gut micro-environment.  The intestine lining is covered with microvilli that are like tiny fingers that stick up—to increase the total surface area for more absorption.”  The surface of the intestine is similar to a big terry cloth towel.

“If there are more nubs sticking up, there will be better absorption of nutrients because there is increased surface area of the microvilli, which improves nutrient absorption,” he explains.