Cattlemen, researchers, veterinarians and nutritionists have known for years that the health of an animal is closely tied to the nutritional plane the animal is on. Animals living with substandard nutrient intake are commonly seen to have any number of complications to overall healthfulness, having a greater problem with resistance to disease and in fact, simply maintaining a normal, productive existence.
An area that has gained quite a bit of attention over recent years is the relationship of mineral nutrition in this picture. Feeding of minerals, while generally accepted as necessary, is probably one of the most misunderstood components of a sound cattle production system. As you go across the country and talk to producer after producer, you normally find that they will have some type of a mineral program. These programs will be very diverse and unfortunately, in many cases, completely unsuitable for a specific cattle operation. And, in many cases, this may be true regarding any component of their nutritional program. In general, however, it seems most common in regard to mineral supplementation. It is vitally important for cattlemen, whether they are commercial or purebred producers, stocker cattle operators or feedyard managers to develop and adopt a sound mineral program in order to be productive and profitable. To help develop a sound program for your area contact a nutritionist specializing in beef cattle, either independent or one affiliated with a feed or mineral company. You can also talk to your veterinarian or local extension agent who should be able to give you some guidelines.
We will discuss here the implications of the producer's mineral program on herd and in following issues continue this discussion on ways that herd health can be improved by improving nutritional status or through the use of other tools available in the industry.
To revisit some basic understandings, minerals are inorganic materials that are involved in countless normal metabolic functions in the body. They are vital to everything from normal bone growth to components of the smallest enzyme involved in the most minute of physiological processes. A deficiency of one can create major complications in normal bodily function, growth or as we are about to see, animal health.
Normally, in cattle diets we consider the macro or major minerals which include Calcium (Ca), Phosphorus (P), Magnesium (Mg), Potassium (K), Sodium (Na), Chlorine (Cl) and Sulfur (S). Micro or trace minerals are Cobalt, (Co), Copper (Cu), Iodine (I), Iron (Fe), Manganese (Mn) Selenium (Se) and Zinc (Zn). The macro minerals are those which are required in larger quantities in the body. Dietary requirements are typically measured in grams per head per day or as a percentage of the diet. Micro minerals are needed in very small quantities and are measured in terms of milligrams per heads per day or in parts per million (ppm) in the diet.
Dietary Sources of Minerals
Over the life of a cow, the majority of her nutrient intake comes from forages, growing, dormant or harvested and stored. This is how God designed her and one of the reasons cattle production is a viable enterprise. In light of this, it is reasonable to assume that since the majority of the cow's nutrient source is from forages, a large percentage of the minerals in her diet are from this source. This is where the complications arise. Forages are highly variable in mineral content in general. Throw into this the effect that previous land use, fertilization, environmental conditions, stage of production and a host of other factors have on the mineral availability and a highly complex feeding/supplementation scenario is created. It is important that the producer is aware of the strengths and weaknesses in the mineral component of his forage program and that he build his mineral program around these circumstances. Additionally, in many cases, in a given area we may encounter a mineral “deficiency” that is apparent not so much from the fact that there is actually a shortage of a given mineral. It may be that there is the existence of a high concentration of another mineral that competes with the mineral in question for an absorption site. This, therefore, creates a deficiency in one mineral simply because not enough is available to overcome this competition with another. There are multitude of interactions between the various minerals both in the digestive tract and in the animal itself.
All this is said to show the importance of the basic mineral program in the cow's diet and also how complicated it can become. As discussed originally, the actual premise of this article is to discuss the interactions of minerals as related to animal health. The preceding discussion simply set the stage.
Animal Health and Mineral Relationships
Animal health can be described as the maintenance of normal physiological functions which allow for a productive existence. A multitude of components must work together to maintain this “steady state” in the animal. The availability of the mineral components in the diet is one very important part of this overall picture. Most significantly the animal's immune system must be maintained. If the immune system is not functioning she cannot be resistant to the various pathogens in the environment. Additionally, without an effective immune system, no amount of vaccination can compensate for this deficiency.
Minerals are not related only to the immune system. If we look at normal calf development, a shortage of calcium, phosphorus and magnesium can lead to impaired skeletal growth and an animal that is not nearly as efficient as it should be, therefore not achieving it's genetic potential. Similarly, these minerals are closely tied to milk production in the cow and can suppress normal milk production if not found in the diet in sufficient amounts. Deficiencies in magnesium has long been tied to conditions such as grass tetany which is a malfunction of the nervous and muscle system. More recent research has shown interactions of calcium and phosphorus in this condition as well. Potassium, Chlorine and Sodium are closely related to movement of water in and out of the cells as well as transmission of nerve impulse across the cell walls.
The Immune System
The immune system in animals (and people) is an amazing mechanism and is quite frankly, not all that well understood. Let's take a minute to examine this system and it's complexity. The animal is able to defend itself from infectious microorganisms by employing three distinct lines of defense. The first and most obvious defense mechanism includes the skin, the lining of the respiratory and gastro-intestinal tracts with accompanying mucous secretions and general body fluid secretions. The skin prevents microorganisms from entering the body, while secretions of sweat, tears and oils kill invading disease-causing organisms. Mucous from the linings of the lungs and respiratory or digestive tracts adhere to bacteria and also contain some bactericidal compounds.
The second defense mechanism involves two types of white blood cells. These cells are found in the blood stream and in lymphoid tissues (thymus, lymph nodes, spleen, bone marrow and areas of the gastro-intestinal tract lining). When the body is damaged or invaded, these cells travel to the injured area where they ingest and destroy alien microorganisms.
Three sub-groups of these white blood cells are produced from stem cells of the bone marrow. These white cells attack some parasites and they also inactivate regulatory compounds released during allergic reactions. Finally, they seek out, ingest and kill bacteria and are part of the defense system against bacterial infections.
Still a different type of white blood cell invade areas of infection and actively ingest bacteria, other foreign material and dead cells. As part of the inflammatory response, these cells follow the first group into the area of infectious inflammation and act as a second line of defense. These cells live in the body a total of about 12 hours. In light of this about 100 billion must be produced every day. Even a slight inhibition can seriously degrade the immune system.
Yet another group of white blood cells act as a third line of defense. The individual cell types are known as T and B cells respectively. Once these cells make contact with an invading organism, it becomes "sensitized" to the specific antigen. The result of this action is a "memory" by the T cells for this particular antigen so that when encountered again, a defense mechanism is already intact. An example of this is the immunization of cattle against Infectious Bovine Rhinotracheitis Virus (IBRV) at which time the T cells will produce antibodies that will bind to IBR but not to unrelated viruses. Once T cells have been sensitized to a particular infectious organism, they are able to act quickly in the event of a recurrence of the attack by the particular organism. The B cells act very similarly
The complexity of this system becomes obvious. As with any type of complex design, biological or otherwise, the increased intricacy will allow the system to become more easily disrupted due to any number of internal or external factors. Such factors may be nutritional imbalances, attack by infectious agents or any of a host of stress conditions. Thus, every precaution must be taken to cover as many bases as possible to insure appropriate nutrients are provided.
Specific Trace Mineral Effects
Two of the trace elements which have been identified to be critical in the function of the immune system are Zinc (Zn) and Copper (Cu). Research has repeatedly shown that many of the important immunological functions discussed above may be adversely affected when Zn is deficient because of it's critical role in the metabolism of nucleic acids and protein. A deficiency in Zn can lead to a deficiency of an enzyme which is then associated with severe T cell deficiency. The granulocytes from individuals with Zn deficiency are shown to be limited in mobility and thus are not capable to move to areas of infection in a timely fashion. The immune system depends on rapid cell production and movement when functioning properly, thus the immune system may be adversely affected during periods of Zn deficiency.
As an aside, dietary shortages are not the only cause of deficiencies. Body Zn levels have been shown to be affected by various stressors, including infectious diseases, transportation, environmental stress, etc., which results in a redistribution of Zn from plasma to the liver which makes it unavailable for many normal processes.
In a similar manner, recent findings suggest that Cu may also play an important role in immune function. Cells involved in the immune response obtained from blood of Cu deficient-calves had a decreased ability to kill ingested microorganisms in the laboratory. Copper deficiency has also resulted in decreased numbers of antibody-producing cells which reduces the ability to fight off antigens.
These studies and scores similar have shown that the deficiency of these minerals as well as many others are closely related to an immune system that does not function properly and therefore does not fight off infection as it was designed. In many cases the deficiency of a given mineral may not be directly related to the functioning of the immune system but may be tied to a system that must operate in conjunction with it in order to maintain a normal state in the body. It also becomes obvious that small discrepancies can have a significant effect on how the animal's body maintains it's healthfulness.
While the contribution of a mineral program to the bottom line is not always apparent, the lack of one will soon show up in terms of decreased production, efficiency and profitability. It is vitally important to have a sound mineral program in place, well matched to your operation and forage programs. In many cases apparent production and health problems are corrected by simply identifying one or more mineral deficiencies or imbalances. A small correction can often lead to significant improvements in your productivity.
Dr. Steve Blezinger is a nutrition and management consultant with an office in Sulphur Springs, TX. He can be reached at 667 CR 4711, TX 75482, by phone at (903) 885-7992 or by e-mail at firstname.lastname@example.org. For more information please visit www.blnconsult.com.