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Journal of Dairy Science Vol. 98 No. 9, 2015
UPDATING AND ASSESSING THE CNCPS FEED LIBRARY
6343
ash contamination could also influence estimates of
kd. Commercial laboratories have addressed this issue
through determination of NDF digestibility on an OM
basis. Using NDF assay with amylase, sodium sulfite
and ash correction (
aNDFom
) in future updates of the
library is recommended to remove variance associated
with ash contamination. Evaluation against laboratory
data compared each individual feed in the feed library
to the mean and SD of the corresponding feed in the
databases available from the commercial laboratories.
Each component within each feed was required to fall
within 1 SD of the mean value from the laboratory data
Table 2.
Equations used by the Cornell Net Carbohydrate and Protein System (CNCPS) to calculate carbohydrate and protein fractions
Fraction
1
Description
Equation
2,3
Equation
no.
CHO
j
Carbohydrates
100 − CP
j
− EE
j
− Ash
j
[1]
CC
j
Indigestible fiber
(aNDFom
j
× (Lignin
j
× aNDFom
j
) × 2.4)/100 or, aNDFom
j
× uNDFom
j
[2]
CB3
j
Digestible fiber
aNDFom
j
− CC
j
[3]
NFC
j
Nonfiber CHO
CHO
j
− aNDFom
j
[4]
CB2
j
Soluble fiber
NFC
j
− CA1
j
− CA2
j
− CA3
j
− CA4
j
− CB1
j
[5]
CA1
j
Volatile fatty acids
Acetic
j
+ Propionic
j
+ (Butyric + Isobutyric)
j
[6]
CA2
j
Lactic acid
Lactic
j
[7]
CA3
j
Other organic acids
Organic acids
j
[8]
CA4
j
WSC
WSC
j
[9]
CB1
j
Starch
Starch
j
[10]
PA1
j
4
Ammonia
Ammonia
j
× (SP
j
/100) × (CP
j
/100)
[11]
PA2
j
Soluble true protein
SP
j
× CP
j
/100 − PA1
j
[12]
PB1
j
Insoluble true protein
CP
j
− (PA1
j
− PA2
j
− PB2
j
− PC
j
)
[13]
PB2
j
Fiber-bound protein
(NDICP
j
− ADICP
j
) × CP
j
/ 100
[14]
PC
j
Indigestible protein
ADICP
j
× CP
j
/ 100
[15]
SUM
j
Sum of composition
100 = CP
j
+ EE
j
+ ash
j
+ NDF
j
+ acetic
j
+ propionic
j
+ isobutyric
j
+ lactic
j
+ + other organic
acids
j
+ WSC
j
+ starch
j
+ soluble fiber
j
[16]
1
Subscript
j
means the
j
th feed in the library.
2
EE = ether extract; WSC = water-soluble carbohydrates; SP = soluble protein; ADICP = acid detergent-insoluble CP; NDICP = neutral
detergent-insoluble CP; aNDFom = NDF assay with amylase, sodium sulfite and ash correction; uNDFom = undigested NDFom after a 240-h
in vitro fermentation and ash correction.
3
Chemical components are expressed as percent DM except: SP = % CP; ADICP = % CP; NDICP = % CP; ammonia = % SP; lignin = %
NDF; uNDFom = unavailable aNDFom, % NDF.
4
Previous versions of the CNCPS feed library use NPN for the PA1 fraction. This has been replaced with ammonia.
Figure 1.
Frequency distributions for corn silage ash (A) and NDF (B) generated using commercial laboratory data sets (n = 21,000;
Cumberland Valley Analytical Services Inc., Maugansville, MD, and Dairy One Cooperative Inc., Ithaca, NY).