Comparison of fractionation methods for nitrogen and starch in maize and grass silages.
In in situ nylon bag technique, many feed evaluation systems use a washing machine method (WMM) to determine the washout (W) fraction and to wash the rumen incubated nylon bags. As this method has some disadvantages, an alternate modified method (MM) was recently introduced. The aim of this study was to determine and compare the W and non-washout (D+U) fractions of nitrogen (N) and/or starch of maize and grass silages, using the WMM and the MM. Ninety-nine maize silage and 99 grass silage samples were selected with a broad range in chemical composition. The results showed a large range in the W, soluble (S) and D+U fractions of N of maize and grass silages and the W, insoluble washout (W-S) and D+U fractions of starch of maize silages, determined by both methods, due to variation in their chemical composition. The values for N fractions of maize and grass silages obtained with both methods were found different (p < 0.001). Large differences (p < 0.001) were found in the D+U fraction of starch of maize silages which might be due to different methodological approaches, such as different rinsing procedures (washing vs. shaking), duration of rinsing (40 min vs. 60 min) and different solvents (water vs. buffer solution). The large differences (p < 0.001) in the W-S and D+U fractions of starch determined with both methods can led to different predicted values for the effective rumen starch degradability. In conclusion, the MM with one recommended shaking procedure, performed under identical and controlled experimental conditions, can give more reliable results compared to the WMM, using different washing programs and procedures.
Animal Nutrition Group, Wageningen University, Wageningen, The Netherlands.|Wageningen UR Livestock Research, Lelystad, The Netherlands.|Institute of Animal Sciences, University of Agriculture, Faisalabad, Pakistan.
M
M
Ali
Animal Nutrition Group, Wageningen University, Wageningen, The Netherlands.
L H
LH
de Jonge
Animal Nutrition Group, Wageningen University, Wageningen, The Netherlands.
J W
JW
Cone
Wageningen UR Livestock Research, Lelystad, The Netherlands.
G
G
van Duinkerken
Product Board Animal Feed, Zoetermeer, The Netherlands.
M C
MC
Blok
BLGG AgroXpertus, Wageningen, The Netherlands.
M H
MH
Bruinenberg
Animal Nutrition Group, Wageningen University, Wageningen, The Netherlands.|Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
W H
WH
Hendriks
D005591:Chemical Fractionation / Q000379:methods*; D005504:Food Analysis; D009584:Nitrogen / Q000737:chemistry*; D006109:Poaceae / Q000737:chemistry*; D012820:Silage / Q000032:analysis*; D013213:Starch / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry*
D013213:Starch; D009584:Nitrogen
modified method; nitrogen; silages; starch; washing machine method