TABLE 20-2Model Abbreviations for Diet and Digestive Macronutrients

NutrientDietaDietaRuminal OutflowDigested or AbsorbedFeces
% of DMkg/d or g/d (_g)
Dry matterDt_DMDt_DMInAn_DigDMFe_DM
WaterAn_WaIn
Total forageDt_ForDt_ForIn
Dry forageDt_ForDryDt_ForDryIn
Wet forageDt_ForWetDt_ForWetIn
ConcentrateDt_ConcDt_ConcIn
PastureDt_PastureDt_PastureIn
AshDt_AshDt_AshIn
Organic matterDt_OMDt_OMInAn_DigOMFe_OM
Residual OMDt_rOMDt_rOMInAn_DigrOMaFe_rOM
NitrogenFe_N_g
Crude proteinDt_CPDt_CPInDu_CPAn_DigCPFe_CP, Fe_InfCP
True proteinDt_TPDt_TPInDu_TPAn_DigTP
Metabolizable proteinDt_MPDt_MPIn
Nonprotein NbDt_NPNDt_NPNInDu_NPN
CP equivalent of NPNbDt_NPNCPDt_NPNCPInDu_NPNCP
DM of NPN sourcebDt NPNDMDt NPNDMInDu NPNDM
Fraction A of CPc_ Dt_CPA_ Dt_CPAIn_
Fraction B of CPDt_CPBDt_CPBIn
Fraction C of CPDt_CPCDt_CPCIn
Ruminally degraded CPDt_RDPDt_RDPIn
Ruminally undegraded CPDt_RUPDt_RUPInDu_RUPDu_idRUPFe_RUP
Microbial CPDu_MiCP_gDu_idMiCP_gFe_MiCP
Microbial NDu_MiN_gDu_idMiN_g
Microbial TPDu_MiTP_gDu_idMiTP_g
Endogenous CPDu_CPend_gFe_CPend_g
Endogenous NDu_Nend_gFe_Nend_g
StarchDt_StDt_StInDu_StAn_DigStFe_St
NDFDt_NDFDt_NDFInDu_NDFAn_DigNDFFe_NDF
Forage NDFDt_ForNDFDt_ForNDFIn
ADFDt_ADFDt_ADFIn
LigninDt_LgDt_LgIn
Fatty acidsDt_FADt_FAInDu_FAAn_DigFAFe_FA
Mcal/kgMcal/d
Gross energyDt_GEDt_GEInFe_GE
Digestible energyDt_DEDt_DEIn
Metabolizable energyDt_MEDt_MEIn
a

Nutrient concentrations and intake from individual feeds are denoted using the prefix Fd_ in place of Dt_. An additional set of concentrations and intakes is calculated for the summation of Dt_Xxx + Inf_Xxx labeled as An_Xxx.

b

NPN refers to nitrogen sources not containing peptide bound or free AAs such as urea or ammonium salts. Values are expressed as N for NPN, in CP equivalents for NPNCP, and as DM for NPNDM.

c

CPA = the CP escaping from an in situ analysis at time 0; CPC = the CP resistant to ruminal degradation at time infinity; CPC = the CP that degrades as a function of time in the rumen.

From: 20, Model Description and Evaluation

Cover of Nutrient Requirements of Dairy Cattle
Nutrient Requirements of Dairy Cattle: Eighth Revised Edition.
National Academies of Sciences, Engineering, and Medicine; Division on Earth and Life Studies; Board on Agriculture and Natural Resources; Committee on Nutrient Requirements of Dairy Cattle.
Washington (DC): National Academies Press (US); 2021 Aug 30.
Copyright 2021 by the National Academy of Sciences. All rights reserved.

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