COMPOSITION OF FEEDSTUFFS USED IN POULTRY DIETS:

Feed formulation involves the correlation of nutrients requirements of the birds with the amounts of various nutrients present in the feed ingredients to be used in formulating a diet. If nutrient concentration found in composition tables are erroneously high, diets formulated on the basis of those values will be deficient even though the dietary concentration are calculated to satisfy the requirements. The desirable solution to the problem would be the actual analysis of each batch of feedstuff before its use in diet formulation. Because of the impracticality of this solution, some reliance must be placed on tabled values for the nutrient composition of feed stuffs. In using the tables it should be recognized that feed stuffs available in particular areas may differ from those described in the tables.

CEREAL GRAINS AND CEREAL BY-PRODUCTS:

The name cereal is given to those members of the graminae which are cultivated for their seeds; cereal grains are essentially carbohydrate concentrates, the main component of the dry matter being starch. The dry matter content of the grain depends on the harvesting method and storage condition but is generally within the range of 80-90%.

The crude protein is most variable component usually ranging from 8-12%. Of the nitrogenous components 86-90% are in the form of proteins but these are deficient in certain essential amino acid particularly lysine and methionine. It has been shown that the value of cereal proteins for promoting growth in young chicks is in the order Oats > Barley > Maize or Wheat. The high relative value of oat protein for growth is probably due to its slightly higher lysine content.

The oil contents of cereal grains vary with species, oats being the richest (5%) and wheat being the poorest (2%). The embryo or germ contains more oil than the endosperm; in wheat e.g.; the embryo has 10-17% oil while the endosperm contains only 1-2%. The embryo of rice is exceptionally rich in oil containing as much as 35%. Cereal oils are unsaturated, the main acids being linoliec and oliec and because of this they tend to become rancid and also produce a soft body fat.

The crude protein content of the harvested grains is highest in those such as oats or rice which contains a husk or hull and lowest in the naked grains, wheat and maize. The husk has a diluent effect on the grain as a whole and reduces the energy value proportionally.

Starch occurs in the endosperm of the grain in the form of granules, whose size and shape vary with different species. Cereal starches consist of about 25% amylose and 75% amylopectin. The cereals are all deficient in calcium containing less than 0.15%. The phosphorus content is higher but part of this is present as phytates. Cereal phytates have the property of being able to immobilize dietary calcium and probably magnesium; oat phytates are more effective in this respect than barley or wheat phytates. The cereal grains are deficient in vitamin D and with the exception of yellow maize in provitamin A. They are good sources of vitamin E and thiamine but have a low content of riboflavin. Most of the vitamins are concentrated in the aleurone layer and the germ of the grain.

VARIABILITY IN CEREAL GRAINS:

Bushel weights (bulk densities) of cereal grains are used in commerce to establish market grades and prices. Bushel weights of grains also have been used as criteria of feeding value and in some instances, those practice seems justified for poultry. For example, at standard moisture level, there is a strong relationship between bushel weight and the general feeding value of oats and barley. An increase in bushel weight of these grains is a reflection of an increase in the proportion of the meaty kernel and a decrease in the proportion of the fibrous hull. Thus there is a definite increase in metabolizable energy and usually protein content of barley and oats as bushel weight increases.