Step 1: Reduce undigested protein
Protein is normally digested in the small intestine and provides amino acids to the animal. Amino acids are the building blocks for protein deposition (growth) and are important for a great number of functions in the body. Unfortunately the protein that we supply via the diet is not 100% digestible. If protein is not digested in the small intestine, it will reach the large intestine and forms a substrate for pathogens (like E. coli) to develop. Too much undigested protein may result in an imbalance of the microflora which leads to digestive disorders like diarrhoea.
On the one hand we want to provide high amounts of protein to the animal for optimal performance, but on the other hand we need a low level of protein to reduce the risk of digestive disorders. This seems a paradox, but with the correct tools, nutritionists are able to manage this very well.
To face this issue it is most relevant to know the exact requirement of the animal for each essential amino acid, the so called ideal amino acid profile. This profile varies between species (pigs vs. poultry) and per stage of life (piglets vs. growers/finishers). Recently a lot of new research has become available that reveals this ideal amino acid profile. Once we know the requirement of each amino acid we can supply a diet that meets this ideal amino acid profile as close as possible. Amino acids in the diet are supplied via protein raw materials and feed grade amino acids.
Currently the first five limiting amino acids (lysine, threonine, methionine, tryptophan and valine) are available in free feed grade form. These feed grade amino acids are 100% digestible, so they do not contribute to undigested protein. The next limiting amino acids (isoleucine, leucine, histidine, etc) should be added via protein rich feedstuffs – most preferably the feedstuffs chosen have a high digestibility. Table 1 shows an ideal amino acid profile in the feed for piglets following the latest results from amino acid dose-response trials.