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Understanding micro nutrients: Why are they important?

By Tracy Meyer, ADVIT Animal Nutrition
Vitamins and minerals constitute a small percentage of the pig diet, but their importance to the health and well-being of the pig cannot be over-emphasised.  About five percent of the total body weight of a pig consists of mineral elements.  These elements are essential for most of the basic metabolic reactions in the body.  They also have a role in the structure of chromosomes, enzymes, nerves, blood, skeleton, hair and milk.  Additionally, they play an important part in reproduction, growth, production and resistance to parasites and disease. Vitamins are required for normal metabolic function; development of normal tissues; and health, growth and maintenance.  Some vitamins can be produced by the pig’s body in sufficient quantities to meet its needs.  Others are present in adequate amounts in feed ingredients commonly used in pig diets.  However, several vitamins need to be added to pig diets to obtain optimal performance.
Vitamin and mineral needs are more critical today than in previous years because of changes in feeding, housing and management systems.  These changes include:
•    Housing pigs indoors has removed the access to soils and grazing crops which would have provided vitamins and minerals.
•    The use of slotted floors has prevented the recycling of faeces, which may be high in B-vitamins and Vitamin K that are synthesised by microorganisms in the large intestine.
•    Reduced usage of multiple protein sources in the diets. When multiple protein sources are used, they may complement each other in providing the vitamin and mineral needs of the pig.
•    The daily feed intake during gestation has decreased, and therefore the dietary vitamin and mineral concentrations must be increased as daily feed intake is decreased. Moving sows from outdoor to indoor housing lowers the maintenance requirements of that sow, and hence the feeding levels are lowered.
•    As the weaning age of pigs decreased, the quality of the diet with regard to all the nutrients becomes more critical.
•    The bioavailability of nutrients in feed ingredients varies and inhibitors/moulds may result in reduced absorption, increasing the requirements for certain vitamins and minerals.
The vitamin and mineral requirements of the pig are also affected by:
•    Health and immune challenges.
•    Temperature changes – especially when moving piglets from environmentally controlled housing to open housing.  Where pigs are housed in open facilities through the entire growth period, seasonal temperature changes will increase the stress on the pig.
•    Stocking density.
•    Physiological age and growth phase
•    Reproduction.
A number of decades ago, vitamins and minerals were added to the diet to protect the animal from a deficiency, but today, health, ecology and economy are the most important reasons for their addition.
When formulating rations and premixes for the pig, nutritionists apply the “barrel analogy” to make sure that the minimum requirement for all individual nutrients is met. Wikipedia describes this as “Liebig’s Law of the Minimum.” This is a principle developed in agricultural science by Carl Spregel (1828) and later popularised by Justus von Liebig.  It states that growth is controlled not by the total amount of recourses available, but by the scarcest resource (limiting factor).  Liebig used the image of a barrel – now called Liebig’s barrel – to explain his law.  Just as the capacity of a barrel with staves of unequal length is limited by the shortest stave, so a plant/animal’s growth is limited by the nutrient in shortest supply.”
It is important to understand from a pig’s perspective, why these vitamins and minerals are required.  The most important minerals and vitamins are listed (right), together with a basic description of their individual role in the body.
The minerals and vitamins in the diet are involved in a complex inter-relationship.  David Watts  (1990) in the Journal of Orthomolecular Medicine made this statement:  “Nutrient interrelationships are complex, especially among the trace elements.  A mineral cannot be affected without affecting at least two other minerals, each of which will then affect two others, etc.
Mineral relationships can be compared to a series of intermeshing gears which are all connected, some directly and some indirectly.  Any movement of one gear (mineral) will result in the movement of all the other gears (minerals).  The extent of effect upon each gear (mineral) will depend on the gear size (mineral quantity), and the number of cogs in the gear (number of enzymes or biochemical reactions the mineral is involved in).  This meshwork of gears goes beyond just the mineral relationships, extending to and affecting the vitamins, hormones and neurological functions.”
There are a vast amount of interactions which can occur, which emphasises the importance of using a certified premix company as your preferred supplier.  It is very important to remember that the computer input to your feed mill, after mixing and what the pig finally eats can be different rations.  The use of a “tonic” on top of your feeding regime may be of benefit to ensure that all the nutrient requirements are met to their individual needs so as not to fall victim to the barrel effect.
Pig Tonic is a concentrated liquid containing vitamins, trace elements, essential amino acids, fatty acids, electrolytes and nucleotides.  It can be used throughout the life cycle, and will benefit the pig when under stress, disease challenge and at times of feed change.
In conclusion, to maximise the genetic growth potential of the pig, it is essential to ensure that the supply of nutrients is at an optimum level.  The vitamin and mineral premix complements the raw materials used in a formulation, guaranteeing that the pig will receive the correct level of nutrition at all times.

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