Minerals are required by the body of the animal for optimum growth, proper muscle and nerve function. In addition, they are essential components of body enzymes, hormones and cells.

There are several minerals that are essential for maintenance, growth, production and reproduction of dairy animals. Minerals required in a large proportion are called macro-minerals and include calcium, phosphorous, sodium, chlorine, potassium, magnesium and sulphur. Macro-minerals are important structural components of bone and other tissues and serve as important constituents of body fluids. They play vital roles in the maintenance of acid base balance, osmotic pressure, membrane electric potential and nervous transmission.

Minerals required in ppm/kg feed are referred to as micro or trace minerals. This group includes cobalt, copper, iodine, iron, manganese, molybdenum, selenium, zinc and chromium. Trace minerals serve as components of enzyme and hormones.

Some inorganic sources of trace minerals are more bioavailable than others (i.e. Sulphates are more bioavailable than Oxides). Organic minerals are the minerals bonded with an organic compound like amino acid, organic acid or carbohydrate. Organic minerals have a better bioavailability than inorganic minerals but they are more expensive. The worldwide trend is to fulfil the basic requirements through inorganic minerals, and top it up with organic minerals as and when required.

In dairy cattle, two key goals are efficient production and reproduction. Minerals play a significant role in herd fertility. They also have a beneficial role to play in resumption of follicular growth and fertility in dairy cows. Trace element deficiency may be linked to retained foetal membranes (Gupta et al 2005), abortion (Mee, 2004) etc. Trace element status of dairy cows is very important for fertility in the following lactation.

Deficiency of selenium and iodine result in high incidence of retained foetal membrane.

Calcium related disorders are common during parturition or within few days of parturition. Calcium deficiency leads to prolonged first oestrus, ovulation, increased incidence of dystocia and retention of placenta.
Sodium deficiency prevents utilisation of protein and energy.

Deficiency of potassium causes muscle weakness. Deficiency of copper leads to early embryonic death and re-absorption of embryo (Miller et al, 1988), increased chances of retained placenta (O’Dell 1990) and low fertility (Howell and Hall, 1930).

Deficiency of molybdenum leads to decreased libido in male and delayed puberty, reduced conception rate and anoestrus condition in female (Sathish Kumar, 2003);
Zinc is essential for proper sexual maturity, reproductive capacity, fertility and normal reproductive events in females (Sathish Kumar, 2003).

Deficiency of manganese causes poor fertility, is responsible for silent estrus and anoestrus condition (Corrah, 1996) and is important for cholesterol synthesis (Keou, 1990)

Conclusion

The requirement of minerals by dairy animals is influenced by several factors including age, stage of pregnancy and stage of lactation. Minerals perform an essential role in dairy cow reproduction and hoof health. Trace minerals play a critical role in proper functioning of enzymes, hormones and cells. Deficiency can and often do result in less than optimal performance and lost opportunity cost, directly affecting the milk production, health, fertility, conception and the overall profitability of the dairy operation.

Minerals are, therefore, a critical part of a successful dairy nutrition programme.