Determination of proteins in different feeds using the in sacco method in comparison to the CNCPS method

The aim of this study was to determine the correlations between the output parameters of the in sacco method and the CNCPS method (Cornell Net Carbohydrate and Protein System). Both methods were tested on 106 samples from the feeds classified into following categories: extracted meal and cakes, cereals, legumes, maize and alfalfa silage, other silages, DDGS (dried distiller’s grains with solubles), oilseeds and various hays. The effective degradability of crude protein (EDg CP) by the in sacco method varied depending on the type of feed from 44.97% (hays) to 82.59% (alfalfa silage). The lowest degradation parameter of rapidly degraded fraction (a=24.3%) and the highest potentially degraded fraction (b=70.52%) were found in oilseeds. Five nitrogen fractions (A, B 1 , B 2 , B 3 , C) were determined according to the CNCPS method. Fraction A (NPN – non-protein nitrogen) was different in examined feed with the highest in silages (44.95% of the total CP). Fraction B 2 represented in tested feeds the highest part of the total CP, (except for silages, legumes, and oilseeds). Fraction B 3 ranged from 1.96% (legumes) to 19.25% (hays) of the total CP. The correlation between EDg CP and soluble fractions was low (r=0.5464) in concentrate feeds, the correlation between EDg and soluble fractions was (r=0.6323) also low in forages.