Characterization of proteins in feeds according to the CNCPS and comparison to in situ parameters

Abstract

Several methods were used for the evaluation of feed protein for rumen degradability and intestinal digestibility of rumen undegraded protein (RUP). The aim of this work was to explore the possibility of using the Cornell method of predicting the fraction RUP. An in situ method was adopted for estimation of degradability parameters (a, b, c) and effective degradable crude protein (EDCP), and five nitrogen fractions (A, B 1 , B 2 , B 3 , and C) were determined according to the Cornell Net Carbohydrate and Protein System (CNCPS). Fifty-one feedstuffs -13 cereals grains, 5 legume seeds, 3 oilseeds, 11 oilseed by-products, 4 distillers dried grains with solubles (DDGS), and 15 silages (maize, lucerne, grass, and grass-clover) -were used in this work. The examined feedstuffs varied widely in nutrient composition. Fraction B 1 (soluble true protein) in forages was small (2.5-5.7% of total N), but it varied to a large extent in concentrates (DDGS 0.9-1.2, legumes 46.5-63.7, oilseeds meal 17.1-51.8% of total N). Fraction B 2 represented a large proportion of the total protein in oil seed meals (44.3-82.6% of total N) and in DDGS (55.8-77.8% of total N), too. Fraction B 3 was relatively small (less than 10% of total N) in all feedstuffs and declined with increasing acid detergent insoluble nitrogen (ADIN) concentration. The concentration of ADIN fraction in feeds affected ruminal degradability. Lucerne silage, with a high content of ADIN (30.9% of total N), had a low effective crude protein (CP) degradability (57%). Correlation between EDCP and fraction A was r = 0.76. A weaker correlation (r = 0.67) was found between in situ parameter "b" and fractions B 2 and B 3 (r = 0.59), respectively. The results show that much more samples of all feed types should be analyzed to obtain results allowing a more exact prediction of CP degradability and RUP.

In situ and in vitro evaluation of crude protein degradation and utilisable crude protein content of barley, rye and triticale grains for ruminants

“…The NPN concentration in cereal grains is relatively low as compared to other feedstuffs (Chrenková et al, 2014;Westreicher-Kristen, Steingass, & Rodehutscord, 2012). Accordingly, only small differences were detected between the sum of the analysed AA and CP concentrations for samples examined in the present study.…”

“…This fraction could lead to high levels of microbial protein synthesis in vitro, which are washed out during in situ incubations. The NPN concentration in cereal grains is relatively low as compared to other feedstuffs (Chrenková et al., ; Westreicher‐Kristen, Steingass, & Rodehutscord, ). Accordingly, only small differences were detected between the sum of the analysed AA (Rodehutscord et al., ) and CP concentrations for samples examined in the present study.…”

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

“…The fraction A for our results of grain meals, rapeseed feeds, pasture forages and silages achieved mean values of 144.9, 206.8, 296.3 and 468.2 g/kg CP, respectively. These findings are in agreement with several authors (Choi et al, 2002;Chrenková et al, 2014;Polat et al, 2014). The same author noted that data on the nitrogen fractions determined according to the CNCPS system of lupine grains were lacking.…”

Determination of ruminal protein degradation of three forages using in vitro protein fractions and in situprotein degradability characteristics

“…The high proportions of SolP, A (NPN) in MS n as a result of intensive protein hydrolysis during ensiling. 21 Similar to our study, Sniffen et al, 11 showed that B 1 fraction of forages is very low. Generally, when forages are conserved through ensiling or drying, there is a shift in the proportion of B 1 and B 2 towards A (NPN) in silage and B 3 in dried forages.…”