Introduction to Vitamins and Minerals

Vitamins and minerals are very important components in the diets of animals. In this post we'll take a look at what vitamins and minerals are, the difference between requirements and allowances and how we determine them, as well as how to work out if an animal is deficient in a particular vitamin or mineral. 
 
Vitamins

Vitamins are organic compounds required in small amounts in the diet that are essential for life. Vitamins are important because they are essential for most metabolic reactions. They act as co-factors for enzymes that are required for carbohydrate, amino acid and fat metabolism and thus the production of ATP for cells.Vitamins can be separated into fat-soluble and water-soluble categories. Those that are fat-soluble are able to be stored in the body and so their deficiencies aren't immediately apparent, there is also a risk of toxicity. They include Vitamins A, D, E, and K. Water-soluble vitamins must be supplied in the diet and have a lower risk of toxicity because they cannot be stored in the body. This group includes the B-Vitamins and Vitamin C.  

Many species require most of these vitamins in their diets in order to function properly. However, ruminants and horses do not require the B-group of vitamins because the microbes in their rumen (or colon for horses) provide this for them. Vitamins are only essential in the diet if the body can't produce them. 

Vitamers are members of the same vitamin family and play similar roles in the body. The vitamers of a particular vitamin each do the same thing but at different efficiencies.   

The stability in the ration and biological activity of a vitamin depends on the vitamin's environment, processing as well as time. In regards to the environment, vitamins may be oxidised and this decreases their biological activity. When vitamins are subjected to heat during processing, the same thing may occur. In addition, the amount of time the vitamin spends in storage with or without other compounds may affect its activity. This is because some compounds may have a protective or deleterious effect on the vitamin. 

Minerals
 
Minerals are the inorganic (elements other than carbon, nitrogen, oxygen or hydrogen) that are required in the diet and are essential for life. The essential minerals are important because the have catalytic functions in cells, as well as physiological and regulatory functions in the body. Macrominerals are those that exist in relatively high concentrations in the diet and body. Trace elements are those that are required in lesser quantities.

Requirements and Allowances

A "minimum requirement" refers to the least amount of a nutrient that will prevent the clinical signs of deficiency or support a well defined biochemical response. It is the amount of the nutrient in the diet that will allow the body to function at 95% of its optimum level. Requirements must maintain concentrations of the nutrient in tissues and storage organs, maintain the concentrations in products, and match the physiological requirements of the body.

A daily allowance is the dietary concentration of a nutrient needed to achieve optimum enzyme activity or tissue stores in a population. Allowances allow for the variation in a population and in practise can sometimes be over-generous and difficult to meet. Allowances are calculated by determining the mean requirement of the vitamin/mineral in a population and adding an additional 3 standard deviations.

Factors That Affect Vitamin and Mineral Requirements

 Characteristics of the animal, such as species, breed, age and physiological state, affect the requirements for vitamins and minerals. In addition dietary factors may affect the requirement too. This includes the chemical form of the element or vitamin, interacting elements or factors in the diet, and the processing or storage of feeds.

How Do We Determine Vitamin or Mineral Requirements?

There are three ways to determine the requirements for a vitamin or mineral:

1. Supplementing the animal with the particular vitamin or mineral and noting whether supplementation improves animal performance. 
2. Feed a diet deficient in the nutrient and measure the animal's response to supplementation
3. Factorial analysis: this is when the minerals are measured through the accumulation in the body, wool and foetus and allows for losses in milk, faeces, urine, sweat, etc. Estimates are made about the storage and excretion of the mineral during various physiological states. The dietary requirement is calculated by using the following formula:

• Dietary Requirement = (E+G+P+L) / A 
  Where:
  A is the coefficient of absorption for the vitamin or mineral
  E = endogenous losses
  G = the amount required per unit growth
  P = the amount required in pregnancy
  L = the amount lost in lactation.

  
  

How Do We Know if an Animal is Deficient in a Mineral?

There are a few ways to tell if an animal is not receiving enough of a particular mineral in its diet. An indirect method is to analyse the soil from which the animal's food grows. One could also analyse the feed that the animal eats to determine if enough of the mineral is present. A more direct method is to take a sample of the animal's tissue and analyse that. A production response trial can also be performed.   

A sequence of events occurs before an animal is deficient in a vitamin or mineral. Firstly, the storage supply of the nutrient is depleted, then the blood plasma stores are used up and then the presence of the nutrient in tissue enzymes. Once the levels of the nutrient in the tissues becomes too low, the onset of clinical signs begins.


That's all for this post, let me know if you have any questions :)