A concentrate is usually described as a feed or feed mixture which supplies primary nutrients (protein, carbohydrate and fat) at higher level but contains less than 18% crude fibre (CF) with low moisture. In general, concentrates are feeds that are high in nitrogen free extract (NFE) and Total Digestible Nutrients (TDN) and low in crude fibre.
On the basis of the crude protein content of air dry concentrates, these are classified as either energy rich concentrates when crude protein (CP) is less than 18% or protein rich concentrates when the CP value exceeds 18%.
Energy sources
These are described under the following categories:
1.1.Grains and seeds
1.2.Milling by-products
1.3.Molasses
1.4.Roots and tubers
1.1. Grains and seeds
Grains are seeds from cereal plants, members of the grass family called Graminaea. Cereal grains are essentially carbohydrates, the main component of the dry matter being starch, which is concentrated on the endosperm. All cereal crops are annuals (Kharif). By- products of harvested grains as chaff, stover and straw are utilized as low quality forages for ruminant animals. Moreover, many of the grains are milled or processed in some manner thereby creating additional by-products which can be fed to livestock with varying degrees of nutritive values. In India except for poultry, swine and lactating d airy animals, grains are not usually fed for livestock production, because of high cost due to high demand by human beings.
The crude protein content of grains and seeds varies between 8-12%, which again is deficient in lysine and methionine. The oil which is mostly present in the embryo is highest in oats (4-6%) and lowest in wheat (1-2%). Cereal oils are unsaturated, the main fatty acids being linoleic and oleic and because of this, the cereals tend to become rancid quickly and also produces soft body fat in non-ruminants. The crude fibre content of harvested grain is highest in oats and rice, which contain a husk or hull formed from the inner and outer paleae and is lowest in the naked grains like wheat and maize. All cereals are deficient in vitamin D and calcium, but are moderately rich in phosphorus and vitamin E.
Cereal grains and cereal by-products
Nutrient composition of grains
The name cereal is given to those members of the Gramineae which are cultivated for their seeds. The dry matter content of grain depends on the method of harvesting and storage conditions but is generally within the range of 80-90%. Protein constitutes 85-90% of the nitrogenous compounds. The protein occurs in all tissues of cereal grains, but higher concentrations are found in the embryo and aleurone layer than in the starchy endosperm pericarp and testa. The protein content of grain though variable, normally ranges from 8-12%. The lipid content of cereal grains also vary with species, normally ranges from 1-6%. Maize and oat contain 4-6% oil, while sorghum 3-4% and wheat, barley and rice
contain 1-3% oil. The embryo or germ contains more oil than the endosperm. Cereal oils are unsaturated, the main acids being linoleic and oleic and because of this, they tend to become rancid quickly.
The crude fibre content of the harvested grains is highest in those such as oats or rice which contain husk and is lowest in grains without husk like wheat and maize. The husk has a diluent effect on the grain as a whole and reduces the energy value of proportionally. Starch occurs in the endosperm of the grain in the form of granules, whose size and shape vary with different species. Cereal starch consists of about 25% amylase and 75% amylopectin, although waxy starches contain greater proportions of amylopectin. The cereals are deficient in calcium and vitamin D. Though phosphorus content is higher, but part of this is present as phytic acid. Cereal phytates have the property of being able to bind dietary calcium and probably magnesium, thus preventing their absorption from the gut. Except yellow maize, all other cereals are low in provitamin A. They are good sources of vitamin E and thiamin, but have a low content of riboflavin. Cereals generally form a lower proportion of the total diet of ruminants.