Crude protein and the metabolisable energy values were two nutrients, based on which, the nutritionists formulated the poultry feed formulae. Gradually, the nutritionists started looking more deeply and included major amino acids like lysine and methionine, major minerals like calcium and phosphorus and major vitamins like A and D. The requirements were recommended by the NRC (National Research Council), which were worked out mostly at the universities long ago.

The breeding companies increased the production potential of the bird by selective breeding and by inventing better hybrid crosses. They employed nutritionists and experimented on the nutrient requirements of the changing genotypes. More and more nutrients were added and revised periodically basing on the performance and the environment. Different levels were recommended for hot climates. Mostly the nutrient levels were being revised upwards with the improved production levels.

The nutrient requirements were differentiated basing on the nature of the bird stocks, the major classes being broilers, layers and broiler breeders. The bodyweight (for maintainance), the weight gain expected, production output and the climate (mostly environment temperature) the bird lives in are the major considerations. Most of these changes up to 2010 were done in the direction of getting the maximum output and conversion efficiency (kilo feed per kilo chicken or eggs). Improving the meat yield and getting better fertility hatchability and chick quality are the additional parameters considered.

The broiler feed formulations have undergone tremendous changes. Four types of formulae, prestarter, starter, grower and the finisher for a 40-day growing cycle of the broiler are prescribed for broilers. Chick, grower, prelayer, layer1, layer2 and layer3 for the layers. Similar diets for female broiler breeders and separate low-protein diets for broiler breeder males were introduced.

Poultry production had gone up in volumes and poultry became a serious competitor to human beings for the major ingredients like grains and vegetable oil. Fish meal and meat meal are being totally replaced by all plant diets for the fear of infections. Dicalcium phosphate replaced the traditional bone meal for similar reason.

Availability and price of the materials necessitated the change in formulations. As the feed prices went up, the nutritionists started using unconventional feed sources like grain byproducts in the place of grains. Corn being replaced by many other grains including wheat or dried distillery grains. Many deoiled cakes like rapeseed, cotton seed in place of de oiled soybean meal with changes and cautious levels. The nutritionists also are looking at the actual requirements critically. Amino acid requirements instead of crude protein. It has been found that the birds are doing well even at a lower level of crude protein if the amino acid requirements are met. The costs of the feed could be economized by reducing the crude protein levels.

The pre-starter and starter diets of broilers have gone up to 23.5 and 22.5 per cent by 2010. The protein levels are being revised downwards and the broiler producers are giving as low as 19.5 per cent and 18 per cent getting similar results. The additional feed consumed per kg of meat is being offset by the price of the lower grade ingredients.

Similarly, the protein requirements of layer birds are being revised to 16 to 16.5 per cent from 18 per cent in spite of the fact that the layer is laying many more eggs and continue to lay more. The levels fed to broiler breeders are still being lowered to 14.5 per cent from 17.5 per cent. The four-kilogram breeder layer is found to require much lesser levels of protein to produce smaller number of eggs.

The available phosphorus was once being supplied from only organic sources like dicalcium phosphate and the levels were increased to 0.7 total phosphorus. The same phosphorus levels are being managed from the phosphorus available in the fibre part of the food digested with the help of phytase enzyme reducing the supplementation of elemental phosphorus to 25 per cent of what it was few years ago.

Re looking in to the present levels of ingredients in the feed formula rather than the usefulness of added levels is going to be the theme of the feed formulation of the next decade. No doubt, this is going to result in substantial savings on the major input - feed.