The improvement of cow genetic merit over recent years has resulted in cows with an exceptionally high production potential; this potential can only be exploited successfully if these cows achieve high nutrient intakes. Ideally as large a portion as possible of this intake should consist of grazed grass, as grass, if efficiently grazed, offers an opportunity to reduce feed costs.

However considering that under ‘perfect’ grazing conditions the upper limit to herbage intake is approximately 17 kg DM/day, capable of producing 27 litres, then it is obvious that grass will often fail to fulfil the nutrient needs of higher producing cows.

As a result supplementary concentrates must be provided with a view to improving performance over and above that which can be produced from pasture alone.

Given the higher responses of high yielding cows concentrate feeding should be targeted to individual cows on a basis of current milk yield. Suggested concentrate feed levels for feeding cows at pasture are presented in Table 1.

Table 1. Suggested concentrate feed levels for cows in early and late season with a herbage allowance of 25kg DM/cow/day above 5cm (Mayne 1996)


The Energy Gap

It is important to be aware of the limitations of grass with regard to energy. The maximum supply of energy, which a cow will receive from grass in “perfect” grazing conditions, is 200 MJ/day. The average 30 litre cow requires 223 MJ/day; 70 MJ for maintenance, 3 MJ for follicle growth and 5 MJ per litre of milk produced. If the energy intake of the cow is deficient, the cow will experience a negative energy balance.

A negative energy balance results in body condition loss and is associated with poor follicle growth and lower conception rates. It is therefore extremely important to provide the cow with additional energy. The benefits are clearly shown in Table 2.


Insufficient Minerals

While grass does supply a portion of minerals, there are a number of minerals that are insufficient. The following graph shows the mineral supply to a typical cow grazing 12 kg grass DM.


Balancing the mineral requirement of the productive cow is essential if optimum productivity is to be achieved therefore it is important to feed a compound that is fortified with minerals.