NET ENERGY OF LACTATION (NEl)The amount of energy in a feed which is available for milk production and body maintenance. Feeds generally are similar in total energy content but vary widely in the proportion of the total energy which is available for maintenance and milk production. The remainder of the energy in the feed is lost in the feces urine, gas belched form the rumen and excess heat production by the cow. In the cow, it takes 0.74 Mcal NEl to produce 1 kg of milk containing 4% fat and the net energy content of most feed range from 0.9 to 2.2 Mcal NEl per kg dry matter.
NEUTRAL DETERGENT FIBER (NDF)A measure of the amount of cell wall in a feed determined by a laboratory procedure. Neutral detergent fiber includes cellulose, hemicellulose and lignin.
NON-FIBER CARBOHYDRATECarbohydrates that are not part of the neutral detergent fiber, but generally accumulate in the plant as energy reserve (e.g., starch). These carbohydrates usually are more rapidly and more completely digested than the fibrous carbohydrates (syn Non-structural carbohydrate).
NON-PROTEIN NITROGEN (NPN)Nitrogen that comes from a source other than protein but may be used by a ruminant in the building of protein. NPN sources include compounds such as urea and anhydrous ammonia, which are used in feed formulations for ruminant only.
NON-STRUCTURAL CARBOHYDRATE(see non-fiber carbohydrate).
NUTRIENTThe chemical substances found in feeds that can be used, and are necessary, for the maintenance, production and health of the animal. The main classes of nutrients are carbohydrates, fats, proteins, minerals, vitamins and water.
NUTRIENT REQUIREMENTThis refers to meeting the animal's need of the various classes of nutrients for maintenance, growth, reproduction, lactation and physical work.