Journal
CZECH JOURNAL OF ANIMAL SCIENCE
Volume 59, Issue 6, Pages 288-295Publisher
CZECH ACADEMY AGRICULTURAL SCIENCES
DOI: 10.17221/7499-CJAS
Keywords
feedstuffs; nitrogen fractions; Cornell Net Carbohydrate and Protein System; in situ method; effective crude protein degradability
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Funding
- European Commission [FP7-KBBE-2007-1]
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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.
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