3 January 2010

3 minute read

Dairy cattle require specific amounts of nutrients to support various levels of performance, so changes in feed intake can have a dramatic impact on the formulation of rations and nutrient intake. Dietary nutrient densities are minimised when feed consumption is maximised, making it easier to formulate rations that are adequate in nutrients. The amount of feed that a dairy cow consumes is highly correlated to its nutrient intake. Every effort should be made to maximise feed consumption when feeding dairy cattle. As feed consumption declines, dietary nutrient densities are increased. The higher the intake, the more forage that can be included in a dairy ration and the fewer concentrates that will be required.

The most cost-effective feeding programmes can be implemented when feed consumption is maximised. Maximised feed consumption minimises the cost of providing required nutrients because higher levels of forages and by-product feeds can be incorporated into the ration. When feed consumption is maximised there is more flexibility in the type of feeds that can be used in formulating the ration.

The quality of forage has a dramatic effect on feed consumption. Feeding the highest-quality forage will maximise feed consumption and nutrient intake and minimise dietary nutrient densities, ration cost and the quantities of concentrates that need to be incorporated into a ration. The feeding of roughages containing high fibre and low digestible energy levels is the primary cause of many dairy farms' failure to realise maximum dry matter intake. Higher forage levels also help to maintain a more stable and healthier rumen and reduce the animal's consumption of grain, which can then be put to other uses, including human consumption.

As forage quality declines, the digestive passage rate becomes slower, resulting in a greater fill factor and causing a reduction in feed intake. When low-quality forages have to be fed, they should be chopped to minimise their depressing effect on feed consumption. Care needs to be taken not to chop forage so fine that milk butterfat is depressed by the resulting low effective fibre level.

Every effort should be taken to minimise heat stress so that feed consumption is not depressed. Shade is very important in areas where cows are exposed to high levels of solar radiation. In hot dry climates, applying water or using misters or evaporative coolers can be effective ways of lowering ambient temperatures, cooling cows and reducing heat stress. Circulating air with fans increases evapotranspiration and increases the dissipation of a cow's body heat load. Opening housing facilities to increase air circulation during times of heat stress increases air movement, which will increase cooling and reduce heat stress. Providing a cool water supply can also help to reduce heat stress.

Adequate consumption of water is critical for maintaining feed consumption; there is a high correlation between feed and water consumption in dairy cattle. When dairy cattle are required to consume poor-quality water, water and feed consumption will be depressed. Maximum performance will only be achieved when cattle have ad libitum access to a good-quality water source.

Poor-quality water or an inadequate supply of water will depress an animal's performance more quickly and more dramatically than any other nutrient deficiency. Adequacy of watering space must also be considered. When cows have to wait too long to drink, their water and dry matter consumption are decreased. If water sources of variable qualities are available, the highest-producing cows should be given the best-quality water.

When developing feeding programmes for dairy cattle, the goal should be to maximise feed consumption by trying to minimise the various factors that depress it. When feed consumption is maximised, performance is optimised, and this should be the primary goal of a dairy feeding programme.