Evaluation of ruminal crude protein degradation of common feeds used in temperate climates

Abstract

The objective of this study was to evaluate the nutritional value of different feeds using chemical analysis and procedures to determine the nitrogen fractions expressed in g/kg of crude protein (CP) using a Cornell system. The experiment includes samples of common feeds used for ruminants in the Czech Republic. Fraction A is most commonly available from silages (average 468.2 g/kg CP) and least available in soybean (83.9 g/kg CP). In contrast, rapidly degradable protein (fraction B1) showed the lowest values in silages (average 31.5 g/kg CP) and the highest values in rapeseed cakes (average 195.7 g/kg CP) and lupines (average 308.7 g/kg CP). The intermediately degradable protein fraction B2 had a high value in almost all of the samples and especially in lupines (average B2 fraction 384.7 g/kg CP). The remaining fractions (B3 and C) represent slowly degraded proteins and unavailable proteins and represented a very small part of CP (average 18.9 and 34.9 g/kg CP, respectively). A strong relationship was found between fraction A and soluble protein (SOLP) and fraction B1 and SOLP. Other strong correlations were found between fraction B2 and CP, B2 and insoluble protein (IP), B3 and IP and B3 and neutral detergent insoluble nitrogen (NDIN).