Explain the Digestibility Coefficient?

You have earlier learnt that dietary proteins are hydrolyzed to amino acids during digestion. The digestion begins in the stomach by the action of pepsin and later completed in the intestines by trypsin, erepsin and other enzymes. Proteins differ in their digestibility. Egg and milk proteins are easily digested and converted into amino acids while pulse proteins are slowly digested to amino acids. Amino acids are absorbed into the blood stream and the un-hydrolyzed portion of the protein is wasted in the faeces. Thus, digestibility coefficient of protein refers to the percentage of the ingested protein absorbed into the blood stream after the process of digestion is complete. When an animal is fed on nitrogen (N)-free diet, certain amount of nitrogen is excreted in the faeces. This is derived mainly from the digestive juices. This is called 'endogenous faecal N.' When a protein food is given, the N found in faeces consists both of endogenous N and food N lost in digestion. To find out N lost in digestion, endogenous faecal N should also be determined. For the determination of the digestibility coefficient, therefore, the data on food nitrogen intake (I,), total faecal nitrogen excreted (F_n) and endogenous faecal nitrogen (F_e) are required. The digestibility coefficient can thus be calculated using the formula:

The digestibility coefficients of proteins are influenced by several factors, such as, the presence of indigestible carbohydrates like cellulose and hemi-cellulose and the presence of proteolytic enzyme inhibitors.