In Vitro Post Ruminal Protein Digestibility of some Commonly Used Feeds and its Prediction from CNCP Based Protein Fractions

The objective of the study was to develop a multiple regression equation for predicting in vitro post ruminal protein digestibility of feeds from different protein fractions. Sixteen feeds viz., maize grain, maize gluten meal, maize fibre, maize oil cake, wheat, wheat bran, barley, soybean meal, sunflower meal, deoiled coconut cake, cottonseed cake, groundnut cake, mustard cake, fish meal, guar churi/chuni and Leucaena leucocephala leaves were incubated in the rumen of three fistulated cattle for 24 h and the dried residues were subjected to pepsin-pancreatin digestion. All the above feeds were also subjected to protein fractionation using phosphate buffer and detergent solutions viz., neutral detergent and acid detergent solutions. Then a multiple regression equation was drawn for post ruminal digestibility from different protein fractions. In vitro post ruminal digestibility of all feeds was high, ranging from 67.68% in sunflower meal to 88.36% in barley. Highest value for A+B₁ fraction (% of total N), the highly degradable fraction was obtained in mustard and groundnut cake followed by barley whereas lowest value was seen in maize gluten meal followed by maize fibre and Leucaena leucocephala leaves. Highest B₂ fraction was found in maize grain followed by Leucaena leucocephala leaves whereas lowest in groundnut cake. However, B₃ and C fractions which have lower and least digestibility in lower tract, was highest in maize gluten meal and lowest in mustard cake, Leucaena leucocephala and wheat bran, respectively. Prediction equation drawn for post ruminal protein digestibility from C fraction alone or B₂, B₃ and C fractions, were significant (P<0.05, 0.02, respectively). Thus, the laboratory analysis of protein fractionation can be used as a method for predicting the protein digestibility of different feeds in lower tract, so in feeds having high content of bypass protein.