Most feeds for dairy cows consist of the stems, leaves, seeds and roots of various plants. Although somewhat arbitrary, this classification is based on the value of a feed to supply a particular nutrient. Nutrients are chemical substances that are necessary for the maintenance, growth, production, reproduction and health of the animal. In addition, certain plants and spoiled feeds contain toxins that are detrimental to the animal's health. When a feed sample is placed in an oven maintained at 105deg.
Feeds contain variable amounts of water.
The amount of water in the feeds is usually of little concern. Milking cows drink from 4 to 5 kg of water for each kg of dry matter they eat. Cows need access to fresh, clean water most of the day. When expressed on a dry matter basis, the concentration of a nutrient in a feed can be compared directly to the concentration of that nutrient required in the diet of the cow. The dry matter of a feed may be divided into organic matter and inorganic matter.