In order to understand the way the feedstuffs are build up it is helpful to check this Diagram I made.
Dry Matter (DM) and water
Basically food is built up from two parts: water and dry matter. When Feeding horses it is important to feed them at least 1 kg DM per 100 kg body weight. It is important to notice that a product does also contain water. Due to this a horse does need more product to reach the needed amount of DM.
example: Horse weight: 500 KG This horse does need 5 KG DM per day
There are three types of roughage commonly fed to horses.
hay: 90% DMM: 5/0,9= 5,55 = feeding minimum 5,6 KG
haylage: 60% DM: 5/0,6= 8,33 = feeding minimum 8,4 KG
Grass Silage: 30 % DM: 5/0,3= 16,67 = feeding minimum 16,7 KG
organic matter and minerals (Ash)
The organic matter does include all biological molecules. This are the structures all living things are build with. Minerals are the non biological molecules in the food. The organic matter can be split up in Fat, Carbohydrates and Proteins. The total percentage of minerals is named Ash In roughage a high Ash percentage could mean there is much sand in there.There are two categories of minerals, macro minerals and micro minerals. The macro minerals like calcium, phosphorous, potassium, magnesium, sodium and sulphur. Selenium, cobalt, iodine, zinc, copper and iron are all micro minerals. Micro minerals are needed in much smaller quanties then macro minerals, hence the name.
Fat or Lipids
Lipid can be divided into two groups; essential and non essential fatty acids. The essential fatty acids in horses are omega 3 & 6 These EFA's need to be added to the diet as the horse is unable to produce these. Omega 9 is manufactured by the horse in quantities that are regarded as adequate to its needs. Fat can be used as a fuel during low intensity exercise. This does mean it is interesting to feed to horses competing in Endurance and Trec. Roughage is usually low in Fat.