Vitamins
|
Vitamins are compounds that are essential for the health of the animal, but which the animal is unable to make for itself. Vitamins must therefore be included in the diet. There are two types of vitamins, those that are soluble in fat or oil (the fat soluble vitamins), and those that are soluble in water (the water soluble vitamins). The requirement for a constant, daily supply of vitamins is different between these two groups of vitamins, as is the danger of toxicity.
Fat soluble vitamins
These vitamins can be stored in the animal’s fat stores (in the liver or the subcutaneous fat). If necessary, once these stores have been built up, the animal can draw on them and so does not require a constant daily supply of fresh vitamins. The adult animal is therefore much less likely to develop a deficiency of any of the fat soluble vitamins unless their diet is deficient in them for a very prolonged period. However, because they do accumulate in the body, it is potentially possible to poison the animal with the fat soluble vitamins since a constant over-supply cannot be efficiently excreted.
The fat soluble vitamins are A, D, E and K
|
Water soluble vitamins
These vitamins are not stored in the animal’s body and so need to be continually included in the diet. However, because they are not stored, there is little risk of them ever reaching toxic concentrations.
The water soluble vitamins are the
B group and Vitamin C.
|
|
|
| Minerals |
There are a number of minerals that are essential for life, and an insufficient supply of them may cause disease or even death. However, it is very rare for deficiencies to occur with most of the minerals, particularly those required in only very small amounts (the trace elements) and indeed problems with some (such as arsenic and lead), although they have an essential role in the body, are usually only encountered when they are in excess and a toxicity situation has occurred. The nutritionally important major and trace elements, and their approximate concentrations in the animal, are given in the table below. Links in this table go to pages with more information on the diseases or problems caused by deficiency (or toxicity) of these minerals.
|
Nutritionally important essential mineral elements
and their approximate concentration in the animal
(McDonald et al., 1995).
Many of the minerals are toxic, especially copper, selenium, molybdenum, fluorine, vanadium and arsenic. Some, like copper, are cumulative poisons. Small quantities ingested with the feed will build up in the body and over time may reach levels at which problems of toxicity start to develop. Although the amount of copper eaten each day may be small, the animal is unable to excrete it efficiently.
|
Different dietary sources of minerals have very different availabilities to the animal. In addition, a number of the minerals interact with each other, so that a surplus of one mineral can induce a deficiency in another even though an otherwise adequate supply of the second mineral is being given.
Minerals are an expensive portion of the diet and, while they are essential, their indiscriminate addition to diets should be avoided because of dangers of toxicity, the unnecessary cost, and the environmental pollution that will be caused by animals having to excrete excessive amounts of minerals in their faeces and urine.
|
|
|
| References and Further Reading |
|
|
McDonald, P., Edwards, R.A., Greenhalgh, J.F.D. and Morgan, C.A. (1995). Animal Nutrition. Fifth Edition. Longman Scientific and Technical, Harlow, UK. p.98. |
|
|
Masters, D.G., Yu Shunxiang, Lu De-Xun and White, C.L. (1995). Mineral Problems in Sheep in
Northern China and Other
Regions of Asia. In: Proceedings of a workshop held in Beijing,
People’s Republic of China, 25-30 September 1995. |
 |
|
|
